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Primary Cardiac and Pericardial Neoplasms: Radiologic-Pathologic Correlation¹

¹ From the Department of Radiology, National Naval Medical Center, Bethesda, Md (M.L.G.); the Departments of Radiologic Pathology (M.L.R., J.R.G.) and Cardiovascular Pathology (A.P.B.), Armed Forces Institute of Pathology, Bldg 54, Rm M-121, 14th and Alaska Sts, NW, Washington, DC 20306-6000; and the Department of Radiology, Georgetown University Hospital, Washington, DC (C.E.G.). Received March 28, 2000; revision requested April 10 and received April 24; accepted April 24. Address correspondence to M.L.R. (e-mail: rosado@afip.osd.mil).

Abstract

Primary cardiac and pericardial neoplasms are rare lesions and include both benign and malignant histologic types. Myxoma is the most frequent primary cardiac neoplasm, but other benign tumors include papillary fibroelastoma, rhabdomyoma, fibroma, hemangioma, lipoma, and paraganglioma. Cardiac sarcoma represents the second most common primary cardiac neoplasm. Lymphoma can also affect the heart primarily. Pericardial tumors that affect the heart include benign teratomas and malignant mesotheliomas. Patients affected with cardiac or pericardial neoplasms often present with cardiovascular compromise or embolic phenomena and exhibit cardiomegaly at chest radiography. Benign cardiac tumors typically manifest as intracavitary, mural, or epicardial focal masses, whereas malignant tumors demonstrate invasive features and may involve the heart diffusely. Benign lesions can usually be successfully excised, but patients with malignant lesions have an extremely poor prognosis.

Index Terms: Heart, neoplasms, 51.31, 51.32, 51.34, 55.329 • Myxoma, 51.311 • Sarcoma, 51.324

LEARNING OBJECTIVES FOR TEST 5

After reading this article and taking the test, the reader will be able to:

• Describe the characteristics and morphologic features of primary cardiac and pericardial neoplasms.
  
• Identify the clinical manifestations that lead to radiologic evaluation for a primary cardiac or pericardial neoplasm.
  
• Enumerate the more common types of primary benign and malignant cardiac and pericardial neoplasms with emphasis on their characteristic radiologic and differential diagnostic features.
  

Introduction

Primary cardiac neoplasms are rare, affect patients of all ages, and have a reported prevalence in autopsy series of 0.001%–0.03% (1). It is estimated that primary cardiac neoplasms are 100–1,000 times less prevalent than secondary neoplasms of the heart. The most common primary cardiac neoplasm is myxoma, which accounts for approximately half of all cases. Other benign primary tumors include papillary fibroelastoma (the most common valvular tumor), rhabdomyoma, fibroma, hemangioma, and lipoma. Although cardiac paraganglioma is almost always benign, rare cases of malignant behavior have been reported (1). Although sarcomas constitute less than 25% of primary cardiac tumors, they represent the second most common primary cardiac neoplasm (2). Rarely, lymphoma may manifest as a primary cardiac tumor. Pericardial neoplasms also affect the heart and may mimic cardiac neoplasia. The two most common pericardial tumors are teratoma and malignant mesothelioma.

Benign neoplasms are usually classified pathologically according to histologic features and cellular differentiation as arising from muscle (rhabdomyoma), fibrous (fibroma), vascular (hemangioma), fat (lipoma), nervous (pheochromocytoma), and ectopic (teratoma) tissues. However, myxoma and papillary fibroelastoma do not fit into any of the above categories. Malignant neoplasms are classified by tissue type as mesenchymal (sarcoma), lymphoid (lymphoma), and mesothelial (mesothelioma) (1).

Patients with primary cardiac neoplasia present with a wide range of symptoms that are most commonly cardiovascular in nature and may mimic more common cardiopulmonary diseases, such as coronary artery disease, cardiomyopathy, pericarditis, and valvular dysfunction. The most common clinical presentation is heart failure (dyspnea, orthopnea, peripheral edema, and paroxysmal nocturnal dyspnea), followed by symptoms caused by peripheral emboli to the cerebral, systemic, and coronary arterial circulations (3,4). The clinical presentation is determined by many factors, including tumor location, size, growth rate, tendency for embolization (friability), and degree of invasiveness. Intracavitary tumors tend to obstruct cardiac valves or major vascular structures or produce emboli; myocardial lesions may affect the conduction system of the heart resulting in arrhythmias; pericardial lesions may lead to pericardial tamponade (3,5,6).

Radiologic evaluation usually begins with chest radiography, which typically reveals abnormal findings including cardiomegaly, signs of heart failure, abnormalities of cardiac contour, and pleural effusions (7). Specific chamber enlargement may result from various intracavitary tumors, whereas mural lesions may produce abnormal contours or cardiac enlargement (8). Pericardial neoplasms usually produce a rapidly developing pericardial effusion (9).

The diagnosis and management of primary cardiac neoplasms has been greatly facilitated by the development of noninvasive cardiac imaging. Although transthoracic echocardiography is useful in the initial evaluation of suspected cardiac tumors (7), transesophageal echocardiography is frequently required for a more comprehensive and accurate assessment (10). Computed tomography (CT) adequately demonstrates the morphology, location, and extent of a cardiac neoplasm, and its main advantage over echocardiography is in its depiction of the pericardium, great vessels, and other structures, which allows the radiologist to look for associated extracardiac disease, including metastases (11,12).

The utility of cardiac-gated magnetic resonance (MR) imaging in the preoperative evaluation of cardiac masses is well established (7,13–19). The wide field of view, high contrast and spatial resolution, and multiplanar imaging capabilities allow precise demonstration and localization of a mass, including its anatomic relationship to the cardiac chambers and any involvement of the myocardium, pericardium, or contiguous structures. In some cases, the use of gadolinium increases the conspicuity of a tumor by showing differential enhancement with respect to the surrounding normal myocardium (17).

In this article, the clinical, pathologic, and radiologic features of primary benign and malignant cardiac and pericardial neoplasms are presented, with emphasis on radiologic-pathologic correlation and differential diagnostic considerations.

Benign Neoplasms

Myxoma
Cardiac myxoma is a benign neoplasm that represents the most common primary tumor of the heart. It is an endocardial mass that occupies the cardiac chamber. Although the majority of myxomas are attached to the fossa ovalis of the interatrial septum, they also attach to the walls of the cardiac chambers and valve surfaces. Approximately 75% of myxomas are found in the left atrium, 20% are located in the right atrium, and rare cases are found in the ventricles (1,20).

Clinical Features.—Cardiac myxoma affects patients aged 11–82 years (mean, 50 years); a female predominance has been reported, with a female-to-male ratio ranging from 1.7:1 to 4:1 (21–23). Myxomas rarely affect children (24). Patients with cardiac myxomas have diverse clinical presentations, which in part depend on the location and morphology of the tumor and its tendency to embolize. Fibrous lesions are more likely to produce valvular obstruction, and polypoid, extensively myxoid lesions are more likely to embolize (20,23). A classic clinical triad of obstructive cardiac symptoms, embolic phenomena, and constitutional symptoms has been described, and most patients have at least one of these signs at presentation (21,22,25). The initial manifestations of atrial myxoma may also resemble those of infective endocarditis and include fever, chills, lethargy, arthralgias, petechiae, and positive blood cultures, although infection of an atrial myxoma is rare (21,26). Approximately 20% of patients with cardiac myxoma are asymptomatic. Physical examination of the majority of patients yields abnormal findings; usually a cardiac murmur is found, but a characteristic "tumor plop" may occasionally be heard (21,25).

The obstructive symptoms caused by cardiac myxomas reflect the size and mobility of the tumor and are seen in over half of affected patients (22); very mobile tumors can cause positional symptoms (25). Left atrial myxomas commonly cause mitral valve obstruction with dyspnea and orthopnea from pulmonary edema or heart failure. Right atrial myxomas may obstruct the tricuspid valve and cause symptoms of right-sided heart failure (20,22).

Embolic phenomena are the second most common manifestation of cardiac myxoma, occurring in approximately 30%–40% of patients (22,23). The most common sites of embolization are the central nervous system, coronary arteries, aorta, kidney, spleen, extremities, and pulmonary arteries. Fatal sequelae of cardiac myxomas are most commonly due to complete mitral or tricuspid valve obstruction by the tumor or to coronary or cerebral embolization (22,25). Constitutional symptoms include myalgia, muscle weakness, arthralgia, fever, fatigue, and weight loss and are seen in approximately 30% of patients. Cardiac arrhythmias, including atrial fibrillation and flutter have been reported in approximately 20% of all patients with cardiac myxomas (21,25).

Two distinct groups of patients with cardiac myxomas have been described. The first group includes patients with myxomas that occur as sporadic lesions. Approximately 86% of these myxomas occur in the left atrium, 94% are single, and the estimated risk of a second myxoma developing after complete excision is 1%–3% (27,28). The second group constitutes 7% of cardiac myxomas. These tumors exhibit an atypical biologic behavior, including multicentricity (45%), atypical location (in cardiac chambers other than the left atrium) (38%), recurrence after surgical excision (12%–22%), and an association with unusual conditions (20%) including the Carney complex. These patients are usually younger (mean age, 28 years), more commonly male, and exhibit a familial predisposition for cardiac myxoma. However, myxomas in both groups are histologically indistinguishable (27–29).

The Carney complex is an autosomal-dominant, inherited disorder in which cardiac myxomas occur in association with cutaneous and mammary myxomas, spotty skin pigmentation, endocrine overactivity (Cushing syndrome, sexual precocity, and acromegaly), psammomatous melanotic schwannoma, primary pigmented nodular adrenal disease, and testicular neoplasms, particularly large cell calcifying Sertoli cell tumor. Cardiac myxoma affects approximately two-thirds of patients with the Carney complex and is its most serious component because of its potentially fatal sequelae. Since 1985, more than 150 patients with the Carney complex have been identified (28,29).

Microscopic Features.—Myxomas are composed of myxoma cells, which have an ovoid nucleus with inconspicuous or large nucleoli, abundant eosinophilic cytoplasm, and indistinct cell borders. Myxoma cells form complex structures including rings, syncytia, and cords that are typically infiltrated by lymphocytes and macrophages. A myxoid background is present in areas without fibrosis. Hemosiderin is present within histiocytes and some myxoma cells (Fig 1a). Fibrosis, thrombosis, and calcification (Fig 1b) are common. Extramedullary hematopoiesis is present in approximately 10% of cases, and mucin-producing glands are present at the base of the tumor in 2% (Fig 1c) (1,20).

View larger version (188K): [in this window] [in a new window] [Download PPT slide]   Figure 1a.   Cardiac myxoma, microscopic features. (a) Low-power photomicrograph (original magnification, x15; hematoxylineosin [H-E] stain) demonstrates a myxomatous stroma containing abundant hemosiderin (dark, granular material most prominent in the upper portion of the photomicrograph). (b) Low-power photomicrograph (original magnification, x75; H-E stain) shows a focus of calcification (central dark staining area) within a myxomatous matrix. (c) High-power photomicrograph (original magnification, x300; periodic-acid Schiff stain) shows nests of myxoma cells (curved arrows) and glandular structures (arrowheads) amid a myxomatous matrix. The glandular differentiation is evidenced by circular lumina and dark red material within the cell cytoplasm (straight arrows).

View larger version (201K): [in this window] [in a new window] [Download PPT slide]   Figure 1b.   Cardiac myxoma, microscopic features. (a) Low-power photomicrograph (original magnification, x15; hematoxylineosin [H-E] stain) demonstrates a myxomatous stroma containing abundant hemosiderin (dark, granular material most prominent in the upper portion of the photomicrograph). (b) Low-power photomicrograph (original magnification, x75; H-E stain) shows a focus of calcification (central dark staining area) within a myxomatous matrix. (c) High-power photomicrograph (original magnification, x300; periodic-acid Schiff stain) shows nests of myxoma cells (curved arrows) and glandular structures (arrowheads) amid a myxomatous matrix. The glandular differentiation is evidenced by circular lumina and dark red material within the cell cytoplasm (straight arrows).

View larger version (176K): [in this window] [in a new window] [Download PPT slide]   Figure 1c.   Cardiac myxoma, microscopic features. (a) Low-power photomicrograph (original magnification, x15; hematoxylineosin [H-E] stain) demonstrates a myxomatous stroma containing abundant hemosiderin (dark, granular material most prominent in the upper portion of the photomicrograph). (b) Low-power photomicrograph (original magnification, x75; H-E stain) shows a focus of calcification (central dark staining area) within a myxomatous matrix. (c) High-power photomicrograph (original magnification, x300; periodic-acid Schiff stain) shows nests of myxoma cells (curved arrows) and glandular structures (arrowheads) amid a myxomatous matrix. The glandular differentiation is evidenced by circular lumina and dark red material within the cell cytoplasm (straight arrows).

View larger version (131K): [in this window] [in a new window] [Download PPT slide]   Figure 2.   Cardiac myxoma, pathologic features. (2) Photograph demonstrates a firm, round lobular mass with a variegated surface.

View larger version (171K): [in this window] [in a new window] [Download PPT slide]   Figure 3.   Photograph of a left atrial myxoma demonstrates a sessile, multilobular, gelatinous mass. A portion of the interatrial septum (arrow) was excised en block with the tumor.

View larger version (109K): [in this window] [in a new window] [Download PPT slide]   Figure 4.   Photograph of a left atrial myxoma demonstrates an elongated, focally hemorrhagic mass with an irregular surface.

View larger version (141K): [in this window] [in a new window] [Download PPT slide]   Figure 5.   Left atrial myxoma in a 41-year-old woman with dyspnea and cough. Posteroanterior chest radiograph shows a prominent left atrial appendage (arrow), pulmonary vascular redistribution, and prominent interstitial markings.

View larger version (143K): [in this window] [in a new window] [Download PPT slide]   Figure 6a.   Right atrial myxoma in an asymptomatic 55-year-old woman with a heart murmur. (a) Posteroanterior chest radiograph demonstrates dense, ovoid, intracardiac calcification (arrows) and borderline cardiac enlargement. (b) Radiograph of the excised specimen demonstrates multifocal, coarse, flocculent tumoral calcification. The densely calcified focus (*) likely represents the calcification seen on radiographs. (c) Photograph of a cut section of the resected specimen shows calcification (*) and hemorrhage (arrows) within the tumor.

View larger version (106K): [in this window] [in a new window] [Download PPT slide]   Figure 6b.   Right atrial myxoma in an asymptomatic 55-year-old woman with a heart murmur. (a) Posteroanterior chest radiograph demonstrates dense, ovoid, intracardiac calcification (arrows) and borderline cardiac enlargement. (b) Radiograph of the excised specimen demonstrates multifocal, coarse, flocculent tumoral calcification. The densely calcified focus (*) likely represents the calcification seen on radiographs. (c) Photograph of a cut section of the resected specimen shows calcification (*) and hemorrhage (arrows) within the tumor.

View larger version (121K): [in this window] [in a new window] [Download PPT slide]   Figure 6c.   Right atrial myxoma in an asymptomatic 55-year-old woman with a heart murmur. (a) Posteroanterior chest radiograph demonstrates dense, ovoid, intracardiac calcification (arrows) and borderline cardiac enlargement. (b) Radiograph of the excised specimen demonstrates multifocal, coarse, flocculent tumoral calcification. The densely calcified focus (*) likely represents the calcification seen on radiographs. (c) Photograph of a cut section of the resected specimen shows calcification (*) and hemorrhage (arrows) within the tumor.

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 7a.   Left atrial myxoma in a 48-year-old man with a 2-year history of intermittent fever. (a) Long axis transesophageal echocardiogram demonstrates a lobular and papillary, heterogeneous, echogenic left atrial mass. (b) Photograph shows the variegated gelatinous mass with multiple excrescences that was excised at surgery.

View larger version (117K): [in this window] [in a new window] [Download PPT slide]   Figure 7b.   Left atrial myxoma in a 48-year-old man with a 2-year history of intermittent fever. (a) Long axis transesophageal echocardiogram demonstrates a lobular and papillary, heterogeneous, echogenic left atrial mass. (b) Photograph shows the variegated gelatinous mass with multiple excrescences that was excised at surgery.

View larger version (126K): [in this window] [in a new window] [Download PPT slide]   Figure 8a.   Left atrial myxoma in a 61-year-old woman with progressively worsening dyspnea. (a) Non-contrast-enhanced chest CT scan (mediastinal window) shows an ovoid left atrial mass that is hypoattenuating with respect to the surrounding blood. (b) Contrast-enhanced chest CT scan (mediastinal window) shows heterogeneous enhancement of the myxoma, which is attached to the interatrial septum. The contrast material-opacified blood outlines the margins of the lobular mass. Note the large bilateral pleural effusions and bibasilar atelectasis.

View larger version (126K): [in this window] [in a new window] [Download PPT slide]   Figure 8b.   Left atrial myxoma in a 61-year-old woman with progressively worsening dyspnea. (a) Non-contrast-enhanced chest CT scan (mediastinal window) shows an ovoid left atrial mass that is hypoattenuating with respect to the surrounding blood. (b) Contrast-enhanced chest CT scan (mediastinal window) shows heterogeneous enhancement of the myxoma, which is attached to the interatrial septum. The contrast material-opacified blood outlines the margins of the lobular mass. Note the large bilateral pleural effusions and bibasilar atelectasis.

View larger version (112K): [in this window] [in a new window] [Download PPT slide]   Figure 9a.   Right atrial myxoma in a 51-year-old woman with abdominal complaints. (a) Contrast-enhanced chest CT scan (mediastinal window) shows a lobular heterogeneous right atrial mass with foci of internal calcification and resultant atrial enlargement. (b) Photograph of the cut specimen shows a lobular, heterogeneous, ovoid mass.

View larger version (138K): [in this window] [in a new window] [Download PPT slide]   Figure 9b.   Right atrial myxoma in a 51-year-old woman with abdominal complaints. (a) Contrast-enhanced chest CT scan (mediastinal window) shows a lobular heterogeneous right atrial mass with foci of internal calcification and resultant atrial enlargement. (b) Photograph of the cut specimen shows a lobular, heterogeneous, ovoid mass.

View larger version (134K): [in this window] [in a new window] [Download PPT slide]   Figure 10a.   Left atrial myxoma in a 71-year-old man with angina and transient ischemic attacks. (a) Axial proton density-weighted ([echo time msec/repetition time msec] 2,769/20) MR image shows a tumor with a heterogeneous appearance: peripheral high signal intensity and central low signal intensity. The high signal intensity likely represents the myxomatous components. (b) Axial cine GRE (50/12) MR image better demonstrates the point of attachment of the tumor. Note the complete loss of signal intensity in the tumor, a finding that may represent a high iron content.

View larger version (106K): [in this window] [in a new window] [Download PPT slide]   Figure 10b.   Left atrial myxoma in a 71-year-old man with angina and transient ischemic attacks. (a) Axial proton density-weighted ([echo time msec/repetition time msec] 2,769/20) MR image shows a tumor with a heterogeneous appearance: peripheral high signal intensity and central low signal intensity. The high signal intensity likely represents the myxomatous components. (b) Axial cine GRE (50/12) MR image better demonstrates the point of attachment of the tumor. Note the complete loss of signal intensity in the tumor, a finding that may represent a high iron content.

View larger version (121K): [in this window] [in a new window] [Download PPT slide]   Figure 11a.   Right atrial myxoma in a 47-year-old woman with prominent neck vein pulsations, fatigue, and headache. (a) Coronal T1-weighted (869/20) MR image demonstrates a spherical heterogeneous mass attached to the lateral wall of the right atrium. (b) Axial T1-weighted (722/20) gadolinium-enhanced MR image demonstrates heterogeneous central foci of enhancement of the myxoma.

View larger version (131K): [in this window] [in a new window] [Download PPT slide]   Figure 11b.   Right atrial myxoma in a 47-year-old woman with prominent neck vein pulsations, fatigue, and headache. (a) Coronal T1-weighted (869/20) MR image demonstrates a spherical heterogeneous mass attached to the lateral wall of the right atrium. (b) Axial T1-weighted (722/20) gadolinium-enhanced MR image demonstrates heterogeneous central foci of enhancement of the myxoma.

View larger version (88K): [in this window] [in a new window] [Download PPT slide]   Figure 12.   Left atrial myxoma in a 52-year-old man with dyspnea on exertion. Axial cine GRE (75/12) MR images, obtained during systole and diastole, demonstrate the point of attachment (arrowheads) to the interatrial septum and the tumor prolapse across the mitral valve (arrow) during diastole. The tumor has an elongated morphology and low signal intensity.

Papillary Fibroelastoma
Clinical Features.—Papillary fibroelastomas are benign endocardial papillomas that predominantly affect the cardiac valves and account for approximately three-fourths of all cardiac valvular tumors (39). Although rare, they represent the second most common primary benign cardiac neoplasm. Papillary fibroelastomas affect men and women equally, and patients have a mean age of 60 years (1,39–41). Most papillary fibroelastomas are found incidentally at the time of autopsy, coronary surgery, echocardiography, or cardiac catheterization. However, affected patients may present with chest pain, transient ischemic attacks or stroke, dyspnea, or sudden death secondary to obstruction of the coronary ostia or embolization. Embolic fragments may arise from the tumor itself or from platelet and fibrin clots that may form on its surface (42,43). The treatment of papillary fibroelastoma is simple surgical excision with possible leaflet repair or valve replacement (42,44,45). Recurrence after surgical resection has not been reported (42,46).

Microscopic Features.—Papillary fibroelastomas are avascular papillomas lined by a single layer of endothelial cells. The core of the tumor is formed by fibrous connective tissue, and there are scattered smooth muscle cells within the papillary projections. The papillary projections may be obliterated by surface thrombosis (1).

Pathologic Features.—Papillary fibroelastomas are gelatinous masses with a characteristic "sea anemone" appearance, produced by multiple narrow branching papillary fronds (Fig 13). The fronds are seen best by immersing the tumor in water. Although papillary fibroelastomas are found mainly on the aortic or mitral valves, away from the valvular free edges, they may also occur on the endocardial surfaces of the atria or ventricles. They are usually solitary lesions that measure 1 cm or less in diameter and attach to the endocardial surface by a pedicle (1).

View larger version (154K): [in this window] [in a new window] [Download PPT slide]   Figure 13a.   Papillary fibroelastoma in a 69-year-old man with chronic atrial fibrillation. (a) Transthoracic four-chamber echocardiogram shows a rounded echogenic mass (arrow) attached to the apex of the left ventricle (LV). LA = left atrium, RA = right atrium, LV = left ventricle. (b) Axial, cine GRE (66/5) MR image demonstrates a 1-cm mass at the apex of the left ventricle (arrowhead). (c) Photograph of the excised specimen shows a gelatinous, multilobular, papillary mass.

View larger version (135K): [in this window] [in a new window] [Download PPT slide]   Figure 13b.   Papillary fibroelastoma in a 69-year-old man with chronic atrial fibrillation. (a) Transthoracic four-chamber echocardiogram shows a rounded echogenic mass (arrow) attached to the apex of the left ventricle (LV). LA = left atrium, RA = right atrium, LV = left ventricle. (b) Axial, cine GRE (66/5) MR image demonstrates a 1-cm mass at the apex of the left ventricle (arrowhead). (c) Photograph of the excised specimen shows a gelatinous, multilobular, papillary mass.

View larger version (106K): [in this window] [in a new window] [Download PPT slide]   Figure 13c.   Papillary fibroelastoma in a 69-year-old man with chronic atrial fibrillation. (a) Transthoracic four-chamber echocardiogram shows a rounded echogenic mass (arrow) attached to the apex of the left ventricle (LV). LA = left atrium, RA = right atrium, LV = left ventricle. (b) Axial, cine GRE (66/5) MR image demonstrates a 1-cm mass at the apex of the left ventricle (arrowhead). (c) Photograph of the excised specimen shows a gelatinous, multilobular, papillary mass.

Rhabdomyoma
Clinical Features.—Cardiac rhabdomyomas represent up to 90% of cardiac tumors in infants and children and are usually discovered in patients less than 1 year of age (1,47). They are benign myocardial hamartomas that are strongly associated with tuberous sclerosis; in fact, approximately 50% of patients with cardiac rhabdomyomas have tuberous sclerosis. The remainder of these tumors occur sporadically or in association with congenital heart disease. Although most infants with tuberous sclerosis have cardiac rhabdomyomas, the prevalence of these lesions in this population decreases with increasing age, because of spontaneous tumor regression and better survival of patients without cardiac tumors (1,48). Most patients are asymptomatic and are discovered at prenatal ultrasonography (US) or through screening. Affected children may be detected in utero because of nonimmune fetal hydrops and fetal death. Other presenting features include tachyarrhythmias, murmurs, and heart failure. Because the majority of cardiac rhabdomyomas regress spontaneously, surgery is not routinely required. However, patients with life-threatening symptoms, usually those secondary to left ventricular outflow tract obstruction or refractory arrhythmias, respond well to surgical excision (47,49–52).

Microscopic Features.—Rhabdomyomas are composed of enlarged, vacuolated cells with sparse cytoplasm that resemble altered myocytes. Cells stain strongly with periodic-acid Schiff stains due to their high glycogen content. "Spider cells" are typical and are characterized by a centrally located nucleus with radial extensions to the cell periphery (Fig 14) (1).

View larger version (195K): [in this window] [in a new window] [Download PPT slide]   Figure 14.   Rhabdomyoma, microscopic features. High-power photomicrograph (original magnification, x300; H-E stain) demonstrates typical vacuolated cells of rhabdomyoma. Cytoplasmic streaming is a typical artifact that results in "spider cells" (arrows).

View larger version (129K): [in this window] [in a new window] [Download PPT slide]   Figure 15a.   Rhabdomyoma in a 3-month-old boy with tachycardia. (a) Coronal T1-weighted (370/25) MR image shows diffuse heterogeneous nodular thickening of the left ventricular myocardium and interventricular septum (arrows). (b) Photograph of the cut autopsy specimen of the heart shows multiple, firm, white nodules distributed throughout the left ventricular myocardium (arrows).

View larger version (115K): [in this window] [in a new window] [Download PPT slide]   Figure 15b.   Rhabdomyoma in a 3-month-old boy with tachycardia. (a) Coronal T1-weighted (370/25) MR image shows diffuse heterogeneous nodular thickening of the left ventricular myocardium and interventricular septum (arrows). (b) Photograph of the cut autopsy specimen of the heart shows multiple, firm, white nodules distributed throughout the left ventricular myocardium (arrows).

Fibroma
Clinical Features.—Cardiac fibroma is a congenital neoplasm that typically affects children, one-third of whom are under 1 year of age at the time of presentation. Although fibroma represents the second most common cardiac neoplasm in children, it is the pediatric cardiac tumor most commonly resected. However, approximately 15% of cardiac fibromas occur in adolescents and adults (40,57,58). The mean age of affected patients is 13 years, with an age range of 0–56 years (57). There is an increased risk of cardiac fibroma in patients with Gorlin (basal cell nevus) syndrome, which is characterized by multiple nevoid basal cell carcinomas of the skin, jaw cysts, and bifid ribs. Less than 14% of these patients have cardiac fibromas (1,59).

Common clinical manifestations in patients with cardiac fibromas are heart failure, arrhythmias, and sudden death. Invasion or compression of the cardiac conduction system with resulting arrhythmia is considered to be the cause of death in most patients who die because of this tumor. One-third of patients are asymptomatic, and their tumors are discovered because of a cardiac murmur detected during physical examination or at chest radiography. Embolic sequelae are not a feature of cardiac fibromas (57,60).

Microscopic Features.—Fibromas occurring in infants are cellular, fibroblast-rich tumors with little collagen, whereas tumors in adults are composed predominantly of collagen (Fig 16). Numerous elastic fibers, identifiable with special stains, are found in over 50% of cases. Foci of calcification, and less commonly ossification, are seen in approximately 50% of cases. Small groups of lymphocytes and mononuclear inflammatory cells may be present, especially surrounding vessels and at the junction with the normal myocardium (1,57).

View larger version (193K): [in this window] [in a new window] [Download PPT slide]   Figure 16.   Fibroma, microscopic features. High-power photomicrograph (original magnification, x150; H-E stain) demonstrates dense collagen bundles in a largely acellular fibroma.

View larger version (136K): [in this window] [in a new window] [Download PPT slide]   Figure 17a.   Cardiac fibroma in a newborn girl in whom anterior myocardial thickening had been noted at prenatal US. (a, b) Axial T1- (354/25) (a) and sagittal T1-weighted (401/25) (b) MR images demonstrate a large homogeneous mural mass of the anterior wall of the right ventricle that nearly obliterates the right ventricular cavity. (c) Intraoperative photograph shows the large right ventricular mural mass (m).

View larger version (155K): [in this window] [in a new window] [Download PPT slide]   Figure 17b.   Cardiac fibroma in a newborn girl in whom anterior myocardial thickening had been noted at prenatal US. (a, b) Axial T1- (354/25) (a) and sagittal T1-weighted (401/25) (b) MR images demonstrate a large homogeneous mural mass of the anterior wall of the right ventricle that nearly obliterates the right ventricular cavity. (c) Intraoperative photograph shows the large right ventricular mural mass (m).

View larger version (125K): [in this window] [in a new window] [Download PPT slide]   Figure 17c.   Cardiac fibroma in a newborn girl in whom anterior myocardial thickening had been noted at prenatal US. (a, b) Axial T1- (354/25) (a) and sagittal T1-weighted (401/25) (b) MR images demonstrate a large homogeneous mural mass of the anterior wall of the right ventricle that nearly obliterates the right ventricular cavity. (c) Intraoperative photograph shows the large right ventricular mural mass (m).

Echocardiography reveals an echogenic mass that may display heterogeneous echogenicity. Multifocal, central tumor calcifications are occasionally identified. The affected myocardium is usually hypokinetic (5,57). CT demonstrates a heterogeneous mural mass and has a high sensitivity for the detection of tumoral calcification. These lesions typically enhance homogeneously or heterogeneously after intravenous administration of contrast material. An associated pericardial effusion may be seen but is not a predominant feature (57).

At MR imaging, cardiac fibromas may manifest as a discrete mural mass or focal myocardial thickening (Fig 17). These lesions appear isointense to hyperintense relative to myocardium on T1-weighted and hypointense on T2-weighted images, findings characteristic of fibrous tissue (13,17,18,57). Contrast-enhanced MR imaging may better delineate the tumor and may demonstrate heterogeneous enhancement. Nonenhancing areas may correlate with poorly vascularized fibrous tissue (17).

Therapy and Prognosis.—The treatment of symptomatic patients with cardiac fibroma is surgical excision, which usually yields satisfactory results. Patients with very extensive tumors that are not entirely resectable can benefit from partial tumor excision (40,57,61). The surgical outcome is less favorable in patients with large masses, severe heart failure at initial presentation, or recurrent arrhythmias in the neonatal period or early infancy (58). Cardiac fibromas may remain stable in size for years or may even regress (57). Postsurgical tumor recurrence is rare (60).

Hemangioma
Clinical Features.—Cardiac hemangiomas are benign vascular tumors that can affect patients of all age groups. These are rare lesions and account for approximately 5%–10% of benign cardiac tumors. Most affected patients are asymptomatic, and the tumor is discovered incidentally (1). Symptomatic patients most commonly present with dyspnea on exertion but may also have chest pain, right-sided heart failure, arrhythmias, pericarditis or pericardial effusion (which may be hemorrhagic), syncope, and sudden death (62–64). Cardiac hemangiomas can occur in the clinical setting of Kasabach-Merritt syndrome, which is characterized by multiple systemic hemangiomas associated with recurrent thrombocytopenia and consumptive coagulopathy (62).

Microscopic Features.—Cardiac hemangiomas are classified as cavernous (composed of multiple thin-walled, dilated vessels), capillary (composed of smaller capillary-like vessels), or arteriovenous (composed of thick-walled dysplastic arteries, venous-like vessels, and capillaries). Endocardial hemangiomas are usually capillary or mixed cavernous-capillary hemangiomas. They often have a myxoid stroma with a sparse inflammatory background. Intramural hemangiomas are histologically diverse and may be capillary, cavernous, or arteriovenous hemangiomas. Intramural cardiac hemangiomas may contain other tissue elements, especially fat, and occasionally fibrous tissue, similar to intramuscular soft-tissue hemangiomas (Fig 18) (1,63).

View larger version (189K): [in this window] [in a new window] [Download PPT slide]   Figure 18.   Hemangioma, microscopic features. High-power photomicrograph (original magnification, x125; H-E stain) shows characteristic dilated vascular channels (curved arrows) interspersed among myocardial cells. There are scattered fat cells within the interstitium (straight arrows).

View larger version (118K): [in this window] [in a new window] [Download PPT slide]   Figure 19a.   Cardiac hemangioma in a 24-year-old pregnant woman with Marfan syndrome and mild aortic root dilatation, who was found to have a left ventricular mass at surveillance echocardiography. (a) Axial T1-weighted (631/11) MR image demonstrates a lobular, pedunculated, intracavitary left ventricular mass (arrow) arising from the posterior papillary muscle (arrowhead). (b) Photograph shows the tan, bosselated mass that was excised at surgery.

View larger version (117K): [in this window] [in a new window] [Download PPT slide]   Figure 19b.   Cardiac hemangioma in a 24-year-old pregnant woman with Marfan syndrome and mild aortic root dilatation, who was found to have a left ventricular mass at surveillance echocardiography. (a) Axial T1-weighted (631/11) MR image demonstrates a lobular, pedunculated, intracavitary left ventricular mass (arrow) arising from the posterior papillary muscle (arrowhead). (b) Photograph shows the tan, bosselated mass that was excised at surgery.

Therapy and Prognosis.—Cardiac hemangiomas can be successfully excised, and surgical resection is the treatment of choice for symptomatic lesions or when the diagnosis is in question. The long-term outcome of patients with surgically treated symptomatic lesions is excellent (62,63). Spontaneous regression of a cardiac hemangioma has been reported (67), and, therefore, surgery may not always be necessary, particularly for extensive but asymptomatic hemangiomas that would require complex and potentially hazardous excision (62).

Lipoma
Clinical Features.—Cardiac lipomas are very rare, benign neoplasms composed of adipose tissue. These tumors are typically found in adult patients but can affect patients of all ages (40,68,69). Although they usually do not cause symptoms, intracavitary lesions can manifest with dyspnea secondary to blood flow obstruction. In addition, involvement of the cardiac conduction system may result in arrhythmias (68–70).

Microscopic Features.—Cardiac lipomas are largely composed of mature adipocytes. Although there may be entrapped myocytes at the interface of the tumor with the myocardium, the myocytes are not distributed throughout the tumor, as they are in lipomatous hypertrophy of the interatrial septum. A capsule is usually present, although it may be focally absent or attenuated. In contrast to lipomatous hypertrophy of the interatrial septum, cardiac lipomas do not contain brown fat cells (1).

Pathologic Features.—Lipomas are circumscribed, spherical, or elliptical masses of homogeneous yellow fat. Although nearly all cardiac lipomas are epicardial lesions occurring at any site on the atrial or ventricular surfaces, they may also occur in endocardial or myocardial locations (Fig 20). Most reported cases of cardiac lipomas are described as single lesions; however, multiple lipomas have been reported in patients with congenital heart defects, tuberous sclerosis, and rarely in an otherwise normal heart (1,68,70).

View larger version (134K): [in this window] [in a new window] [Download PPT slide]   Figure 20a.   Intracardiac lipoma in a 45-year-old woman with palpitations. (a, b) Axial (a) and coronal (b) proton density-weighted (1,091/20) MR images demonstrate a smooth, round, intracavitary right atrial mass with a signal intensity characteristic of fat. (c) Photograph of the specimen demonstrates a well-circumscribed, spherical, yellow mass that was excised from the right atrium.

View larger version (151K): [in this window] [in a new window] [Download PPT slide]   Figure 20b.   Intracardiac lipoma in a 45-year-old woman with palpitations. (a, b) Axial (a) and coronal (b) proton density-weighted (1,091/20) MR images demonstrate a smooth, round, intracavitary right atrial mass with a signal intensity characteristic of fat. (c) Photograph of the specimen demonstrates a well-circumscribed, spherical, yellow mass that was excised from the right atrium.

View larger version (83K): [in this window] [in a new window] [Download PPT slide]   Figure 20c.   Intracardiac lipoma in a 45-year-old woman with palpitations. (a, b) Axial (a) and coronal (b) proton density-weighted (1,091/20) MR images demonstrate a smooth, round, intracavitary right atrial mass with a signal intensity characteristic of fat. (c) Photograph of the specimen demonstrates a well-circumscribed, spherical, yellow mass that was excised from the right atrium.

Therapy and Prognosis.—Cardiac lipomas are treated with surgical resection, and patients generally have a good outcome (72). Lipomas that encase or displace the coronary arteries or deeply infiltrate the heart may not be resectable. An asymptomatic lipoma that slowly and progressively enlarged over several years of follow-up has been reported (69). A case of an enormous cardiac lipoma, which encased and compressed the heart and resulted in severe cardiopulmonary compromise and death, has also been reported (71).

Paraganglioma
Clinical Features.—Cardiac paragangliomas are extremely rare neoplasms that arise from intrinsic cardiac paraganglial (chromaffin) cells, which are normally predominantly located within the atria. Most lesions have been reported in adult patients with an age range of 18–85 years (mean age, 40 years) (73). The majority of reported cardiac paragangliomas have been catecholamine-producing tumors, and affected patients present with arterial hypertension, headache, palpitations and flushing, (symptoms typical of pheochromocytoma) (73,74). The biochemical laboratory abnormalities that lead to the diagnosis of a paraganglioma include elevated levels of urinary norepinephrine, vanillylmandelic acid, and total metanephrine or elevated levels of plasma norepinephrine and epinephrine (74). Up to 20% of patients with cardiac paragangliomas have associated paragangliomas in other locations (carotid body, adrenal gland, bladder, paraaortic), and approximately 5% of patients will have osseous metastases (73,75).

Microscopic Features.—Paragangliomas are monomorphous tumors composed of nests of paraganglial cells (classically described as "zellballen") surrounded by sustentacular cells (Fig 21). The histologic appearance and immunohistochemical profile of these lesions are identical to those of extracardiac paragangliomas. Immunohistochemical or ultrastructural analysis is often necessary to document the endocrine features of these tumors (1).

View larger version (228K): [in this window] [in a new window] [Download PPT slide]   Figure 21.   Paraganglioma, microscopic features. High-power photomicrograph (original magnification, x300; H-E stain) demonstrates the classic nesting (zellballen) appearance of the paraganglial cells.

Radiologic Features.—Radiologic evaluation of patients with cardiac paragangliomas usually follows biochemical diagnosis of the lesion. If abdominal CT or MR imaging studies fail to reveal a typical adrenal pheochromocytoma, iodine-131 metaiodobenzylguanidine (I-131 MIBG) scintigraphy is used to localize the occult lesion because its sympathetic tissue actively takes up the radiotracer and stores it in catecholamine granules (74,76,77). I-131 MIBG can be used for total body imaging with a sensitivity of approximately 90% (75,77,78).

Because cardiac paragangliomas are typically located in the roof of the left atrium, chest radiography usually demonstrates a middle mediastinal mass that splays the carina and simulates left atrial enlargement (75). Dynamic, contrast-enhanced chest CT reveals a markedly enhancing mass adherent to or involving the left atrium or, less commonly, located anterior to the aortic root. Approximately half of these lesions have central areas of low attenuation, most likely representing necrosis. Tumoral calcification may also be identified. Cardiac paragangliomas may be missed on unenhanced or poorly enhanced chest CT scans because they are commonly isoattenuating with adjacent cardiovascular structures. However, it should be noted that intravenous administration of contrast material can trigger a hypertensive crisis in patients with these lesions and therefore premedication with alpha and beta blockers is necessary (74,75,78).

MR imaging typically demonstrates a mass that is hypointense on T1-weighted and very hyperintense on T2-weighted images. The intrapericardial location of the mass and its relationship to the cardiovascular structures is usually clearly demonstrated (Fig 22) (74–76,78). Coronary angiography optimally shows the relationship of the coronary arteries to the mass, including the blood supply to this highly vascular tumor. This information is critical in the preoperative assessment of these patients (73,74,79).

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 22a.   Cardiac paraganglioma in a 13-year-old boy with a heart murmur and hypertension. (a) Axial T1-weighted (400/20) MR image demonstrates a round, lobular mass of intermediate signal intensity arising from the interatrial septum and protruding into both atria. (b) Axial proton density-weighted (2,000/20) MR image shows an increase in tumor signal intensity. Intraoperative palpation of this paraganglioma resulted in immediate, severe hypertension and tachycardia.

View larger version (134K): [in this window] [in a new window] [Download PPT slide]   Figure 22b.   Cardiac paraganglioma in a 13-year-old boy with a heart murmur and hypertension. (a) Axial T1-weighted (400/20) MR image demonstrates a round, lobular mass of intermediate signal intensity arising from the interatrial septum and protruding into both atria. (b) Axial proton density-weighted (2,000/20) MR image shows an increase in tumor signal intensity. Intraoperative palpation of this paraganglioma resulted in immediate, severe hypertension and tachycardia.

Teratoma
Clinical Features.—Pericardial teratoma is a benign germ cell neoplasm that typically affects infants and children, who present with respiratory distress and cyanosis secondary to pericardial tamponade and compression of right-sided vascular structures (aortic root, superior vena cava, right atrium, and pulmonary artery) (82–84). Pericardial teratomas have been discovered at prenatal US, which typically shows an intrapericardial, multilocular cystic mass associated with pericardial effusion and findings typical of fetal hydrops (ascites, pleural effusions, subcutaneous edema, and polyhydramnios). Pericardial tamponade is a common cause of fetal death in affected patients (85–87).

Microscopic Features.—Microscopically, cardiac teratomas are similar to benign extrapericardial teratomas. Typically, they contain derivatives of all three germ layers, with mature endodermal, mesodermal, and ectodermal elements (Fig 23) (1). Tissues discovered in intrapericardial teratomas are diverse and include neuroglia, cartilage, skeletal muscle, liver, intestine, pancreas, and glandular tissue.

View larger version (187K): [in this window] [in a new window] [Download PPT slide]   Figure 23.   Mature teratoma, microscopic features. Low-power photomicrograph (original magnification, x75; Masson trichrome stain) demonstrates neuroretinal (ectodermal) (thin arrow) and glandular (endodermal) (thick arrows) structures. The blue staining material (arrowheads) is connective (mesodermal) tissue.

View larger version (129K): [in this window] [in a new window] [Download PPT slide]   Figure 24a.   Mature teratoma in a 2-year-old girl with respiratory distress and cardiomegaly. (a, b) Posteroanterior (a) and collimated posteroanterior (b) chest radiographs demonstrate an enlarged cardiac silhouette and a tooth (arrow) that projects over the anterior heart. (c) Axial T1-weighted MR image shows the large, heterogeneous, lobular multicystic pericardial mass.

View larger version (134K): [in this window] [in a new window] [Download PPT slide]   Figure 24b.   Mature teratoma in a 2-year-old girl with respiratory distress and cardiomegaly. (a, b) Posteroanterior (a) and collimated posteroanterior (b) chest radiographs demonstrate an enlarged cardiac silhouette and a tooth (arrow) that projects over the anterior heart. (c) Axial T1-weighted MR image shows the large, heterogeneous, lobular multicystic pericardial mass.

View larger version (149K): [in this window] [in a new window] [Download PPT slide]   Figure 24c.   Mature teratoma in a 2-year-old girl with respiratory distress and cardiomegaly. (a, b) Posteroanterior (a) and collimated posteroanterior (b) chest radiographs demonstrate an enlarged cardiac silhouette and a tooth (arrow) that projects over the anterior heart. (c) Axial T1-weighted MR image shows the large, heterogeneous, lobular multicystic pericardial mass.

View larger version (153K): [in this window] [in a new window] [Download PPT slide]   Figure 25a.   Mature teratoma in a 1-month-old girl with heart failure. (a) Sagittal T1-weighted (560/25) MR image demonstrates a large, heterogeneous anterior pericardial mass that compresses the cardiac chambers and displaces the heart posteriorly. There is a large pericardial effusion (arrow). (b) Photograph of a cut specimen of the tumor shows a firm, white lobular, multilocular cystic mass.

View larger version (81K): [in this window] [in a new window] [Download PPT slide]   Figure 25b.   Mature teratoma in a 1-month-old girl with heart failure. (a) Sagittal T1-weighted (560/25) MR image demonstrates a large, heterogeneous anterior pericardial mass that compresses the cardiac chambers and displaces the heart posteriorly. There is a large pericardial effusion (arrow). (b) Photograph of a cut specimen of the tumor shows a firm, white lobular, multilocular cystic mass.

Malignant Neoplasms

Sarcomas
Sarcomas are rare malignant mesenchymal neoplasms; however, they constitute the majority of primary malignant cardiac neoplasms and the second most common primary cardiac tumor (2). Primary cardiac sarcomas by definition are confined to the heart or pericardium at the time of diagnosis with no evidence of extracardiac primary neoplasm. Although all types of sarcomas affect the heart, the most common cell types are angiosarcoma (37% of cases), unclassified or undifferentiated sarcoma (24%), malignant fibrous histiocytoma (MFH) (11%–24%), leiomyosarcoma (8%–9%), and osteosarcoma (3%–9%). Approximately 10% of surgically resected cardiac tumors are primary sarcomas. Although the majority of angiosarcomas occur in the right atrium, the other cell types more commonly affect the left atrium, an important differentiating feature (1,2).

Clinical Features.—Primary cardiac sarcomas affect adults (mean age at presentation, 41 years) and are extremely rare in infants and children. Patients with leiomyosarcoma typically present 5–10 years earlier than those with other cardiac sarcomas. Angiosarcoma and osteosarcoma are approximately twice as common in men (1,89), and a slight female predominance has been suggested in patients with MFH (90).

The majority of patients with cardiac sarcoma present with cardiopulmonary symptoms with a mean duration of approximately 5 months (1). Dyspnea is the most common presenting complaint. Patients may also present because of pericardial tamponade, embolic phenomena, chest pain, syncope, pneumonia, fever, arrhythmias, peripheral edema, and sudden death (2,89,91,92). Primary cardiac sarcomas most commonly metastasize to the lungs but also to lymph nodes, bone, liver, brain, bowel, spleen, adrenal glands, pleura, diaphragm, kidneys, thyroid, and skin (1,2,89).

Because approximately 80% of cardiac angiosarcomas occur in the right atrium and involve the pericardium, symptoms from right-sided heart inflow obstruction or cardiac tamponade are common. The location and degree of invasiveness of these lesions makes them less likely to be confused clinically with myxomas. The diagnosis of angiosarcoma is often based on biopsy of metastases, which are found in 66%–89% of patients at the time of presentation (1,40). The in utero occurrence of a right atrial angiosarcoma that manifested with a pericardial effusion has been reported (93).

Cardiac sarcomas that typically affect the left atrium are MFH, osteosarcoma, and leiomyosarcoma. Affected patients present with symptoms of mitral valve obstruction, most commonly dyspnea and heart failure. Although the point of tumor attachment is usually not at the fossa ovalis, these sarcomas are often clinically mistaken for myxomas (1,40,90,91).

Microscopic Features.—The histologic appearance of cardiac sarcomas is widely variable. Virtually all types of sarcomas found in the soft tissues have also been described in the heart, the most commonly described being angiosarcoma (Fig 26). Many of the myofibroblastic sarcomas (including MFH, leiomyosarcoma, and osteosarcoma) may demonstrate a prominent myxoid stroma and should not be confused with the benign myxoma. Unclassifiable and undifferentiated sarcomas lack specific histologic, ultrastructural, or immunohistochemical features (1,2).

View larger version (181K): [in this window] [in a new window] [Download PPT slide]   Figure 26.   Angiosarcoma, microscopic features. High-power photomicrograph (original magnification, x450; H-E stain) demonstrates irregular anastomosing vascular channels lined by atypical endothelial cells.

View larger version (116K): [in this window] [in a new window] [Download PPT slide]   Figure 27a.   Unclassified sarcoma in a 29-year-old man with cough, fever, and weight loss who underwent heart transplantation. (a) Coronal T1-weighted (714/12) MR image shows a large, invasive mass of intermediate signal intensity involving the left side of the heart. (b) Photograph of the excised heart shows the nodular mass invading the left atrial wall and mitral valve.

View larger version (91K): [in this window] [in a new window] [Download PPT slide]   Figure 27b.   Unclassified sarcoma in a 29-year-old man with cough, fever, and weight loss who underwent heart transplantation. (a) Coronal T1-weighted (714/12) MR image shows a large, invasive mass of intermediate signal intensity involving the left side of the heart. (b) Photograph of the excised heart shows the nodular mass invading the left atrial wall and mitral valve.

CT is helpful in the evaluation of cardiac sarcomas as it demonstrates the broad-based tumor attachment; myocardial, pericardial, and mediastinal invasion; as well as extension into the great vessels and pulmonary metastases, when present (11,12). Angiosarcomas have been described as highly vascular right atrial tumors with pericardial extension and low-attenuation areas.

Optimal evaluation of cardiac sarcomas is accomplished with cardiac-gated MR imaging, which typically demonstrates large, heterogeneous, broad-based masses that frequently occupy most of the affected cardiac chamber or multiple chambers (Figs 27, 28a). Pericardial and extracardiac invasion, valvular destruction, tumor necrosis, and metastases are frequently seen and are all characteristic features of malignant lesions. Pericardial invasion is characterized by disruption, thickening, or nodularity. Cardiac sarcomas enhance heterogeneously, with non-enhancing areas typically corresponding to necrosis (91,97,98).

View larger version (121K): [in this window] [in a new window] [Download PPT slide]   Figure 28a.   Angiosarcoma in a 28-year-old woman who presented with mitral valve obstruction. (a) Axial contrast-enhanced chest CT scan (mediastinal window) shows a large nodular, homogeneous, soft-tissue mass that invades the right atrium and encases the heart. (b) Coronal T2-weighted (3,780/57) MR image demonstrates extensive circumferential cardiac involvement by the nodular, heterogeneous, hyperintense tumor, which invades the right atrium and encases the heart.

View larger version (135K): [in this window] [in a new window] [Download PPT slide]   Figure 28b.   Angiosarcoma in a 28-year-old woman who presented with mitral valve obstruction. (a) Axial contrast-enhanced chest CT scan (mediastinal window) shows a large nodular, homogeneous, soft-tissue mass that invades the right atrium and encases the heart. (b) Coronal T2-weighted (3,780/57) MR image demonstrates extensive circumferential cardiac involvement by the nodular, heterogeneous, hyperintense tumor, which invades the right atrium and encases the heart.

Therapy and Prognosis.—Primary cardiac sarcomas are highly aggressive lesions that are uniformly fatal. The mean survival of affected patients is from 3 months to 1 year, although survivals of over 4 years have also been reported (1,2,94,99). Pathologic features that predict a better prognosis include tumor origin in the left atrium, low mitotic count, absence of necrosis, and absence of metastases at the time of diagnosis (2,40). Aggressive surgery offers significant palliation of symptoms (caused by valvular and vascular obstruction) and improves survival (89,92,94). Even after complete tumor excision, however, local recurrence and metastatic disease occur frequently and early, usually within 1 year (2,90,94). Heart transplantation has been performed in some patients with unresectable cardiac sarcoma with satisfactory results (92,95,100). Chemotherapy and radiation therapy have not proved beneficial for the treatment of affected patients (92). Death in these patients usually results from postoperative complications, cardiopulmonary failure from progressive tumor growth, and metastatic disease (2).

Primary Cardiac Lymphoma
Clinical Features.—Primary cardiac lymphomas are typically of the non-Hodgkin type. By definition, these tumors involve only the heart or pericardium at the time of diagnosis, with no evidence of extracardiac lymphoma (1,101). Although 16%–28% of patients with disseminated lymphoma have cardiac involvement, primary cardiac lymphoma is very rare. It is seen with greater frequency in immunocompromised patients, particularly in association with the acquired immunodeficiency syndrome, and should be suspected clinically when these patients present with cardiac complaints (102–104). However, immunocompetent patients may also be affected. The mean age at presentation is approximately 60 years, with a reported age range of 13–90 years. A slight male predominance has been reported (1,101).

Patients present with unresponsive, rapidly progressive heart failure, arrhythmias, chest pain, cardiac tamponade, and superior vena cava syndrome. Most primary cardiac lymphomas are either diagnosed at autopsy or are fatal soon after diagnosis. The prognosis for patients with primary cardiac lymphoma is very poor. However, early diagnosis and institution of chemotherapy may result in remission of disease, palliation of pain, and longer survivals. There is no evidence that surgery improves prognosis, although tumor debulking may be an effective palliative procedure (1,101,104,105).

Microscopic Features.—The majority of cardiac lymphomas are B-cell neoplasms (Fig 29). These tumors display a wide range of histologic types, including well-differentiated B-cell lymphomas, follicular center cell lymphomas, diffuse large cell lymphomas, and undifferentiated Burkitt-like lymphomas. Typically, cardiac lymphomas infiltrate the surrounding muscle and epicardial fat and may infiltrate the adventitia of the coronary arteries (1).

View larger version (210K): [in this window] [in a new window] [Download PPT slide]   Figure 29.   Lymphoma, microscopic features. High-power photomicrograph (original magnification, x300; H-E stain) demonstrates lymphoma cells (dark blue round cells) surrounding and infiltrating residual myocytes (arrow).

View larger version (119K): [in this window] [in a new window] [Download PPT slide]   Figure 30a.   Primary cardiac lymphoma in a 75-year-old woman with progressive dyspnea, superior vena cava syndrome, and atrial fibrillation. (a) Coronal T1-weighted (571/12) MR image shows vena caval invasion (arrow) by a mass. (b) Superior vena cavogram demonstrates the large intraluminal tumor that obstructs the vena cava. Note the collateral blood flow through the azygos and hemiazygos veins. (c) Photograph of the specimen of the heart obtained at autopsy shows a firm, white, multinodular right atrial tumor with plaquelike pericardial infiltration (arrow) and obstruction of the superior vena cava (*).

View larger version (125K): [in this window] [in a new window] [Download PPT slide]   Figure 30b.   Primary cardiac lymphoma in a 75-year-old woman with progressive dyspnea, superior vena cava syndrome, and atrial fibrillation. (a) Coronal T1-weighted (571/12) MR image shows vena caval invasion (arrow) by a mass. (b) Superior vena cavogram demonstrates the large intraluminal tumor that obstructs the vena cava. Note the collateral blood flow through the azygos and hemiazygos veins. (c) Photograph of the specimen of the heart obtained at autopsy shows a firm, white, multinodular right atrial tumor with plaquelike pericardial infiltration (arrow) and obstruction of the superior vena cava (*).

View larger version (133K): [in this window] [in a new window] [Download PPT slide]   Figure 30c.   Primary cardiac lymphoma in a 75-year-old woman with progressive dyspnea, superior vena cava syndrome, and atrial fibrillation. (a) Coronal T1-weighted (571/12) MR image shows vena caval invasion (arrow) by a mass. (b) Superior vena cavogram demonstrates the large intraluminal tumor that obstructs the vena cava. Note the collateral blood flow through the azygos and hemiazygos veins. (c) Photograph of the specimen of the heart obtained at autopsy shows a firm, white, multinodular right atrial tumor with plaquelike pericardial infiltration (arrow) and obstruction of the superior vena cava (*).

Pericardial Mesothelioma
Pericardial mesothelioma is a malignant primary neoplasm that arises from the mesothelial cells of the pericardium. The term is used to describe those tumors localized to the pericardium and does not apply to primary pleural tumors that secondarily invade the pericardium. Although pericardial mesotheliomas represent less than 1% of all malignant mesotheliomas (1), they account for 50% of all primary pericardial tumors (107).

Clinical Features.—Patients with pericardial mesotheliomas range in age from 2 to 78 years, with a mean age of 46 years and a 2:1 male-to-female ratio. Clinical symptoms include chest pain, cough, dyspnea, and palpitations. Patients with diffuse pericardial involvement may present with symptoms and signs that mimic pericarditis or cardiac tamponade. Patients with advanced tumors may present with widespread metastases. Although there appears to be some causal effect of asbestos exposure, a definite association has not been established due the rarity of this lesion. Surgery combined with radiation therapy may be palliative, but the prognosis of all patients (even those who are treated) is extremely poor, with survivals of 6 months to 1 year after diagnosis (1,107).

Microscopic Features.—Malignant mesothelioma is typically a biphasic tumor composed of epithelial areas, which resemble a carcinoma, and spindled areas similar to a sarcoma. The epithelial areas form tubulopapillary structures (Fig 31). The spindled areas usually demonstrate some evidence of mesotheliomatous differentiation when examined with ultrastructural or immunohistochemical techniques. Other microscopic features include necrosis and extensive cellular pleomorphism (1). Cytologic examination of pericardial fluid is frequently nondiagnostic because of the difficulties in differentiating malignant mesothelioma cells from reactive cells (107,108).

View larger version (189K): [in this window] [in a new window] [Download PPT slide]   Figure 31.   Mesothelioma, microscopic features. High-power photomicrograph (original magnification, x400; H-E stain) demonstrates tubulopapillary structures (arrow) characteristic of epithelial mesothelioma.

View larger version (117K): [in this window] [in a new window] [Download PPT slide]   Figure 32a.   Pericardial mesothelioma in a 36-year-old woman with fatigue, malaise, and dyspnea. (a) Axial contrast-enhanced chest CT scan (mediastinal window) demonstrates a lobular, heterogeneous left pericardial mass with a large pericardial and bilateral pleural effusions. Note the large areas of low attenuation (arrow), likely representing necrosis, within the tumor. (b) Photograph of the cut specimen of the heart obtained at autopsy shows a diffuse nodular pericardial mass that encases the heart. Scale is in centimeters.

View larger version (141K): [in this window] [in a new window] [Download PPT slide]   Figure 32b.   Pericardial mesothelioma in a 36-year-old woman with fatigue, malaise, and dyspnea. (a) Axial contrast-enhanced chest CT scan (mediastinal window) demonstrates a lobular, heterogeneous left pericardial mass with a large pericardial and bilateral pleural effusions. Note the large areas of low attenuation (arrow), likely representing necrosis, within the tumor. (b) Photograph of the cut specimen of the heart obtained at autopsy shows a diffuse nodular pericardial mass that encases the heart. Scale is in centimeters.

Differential Diagnosis

The differential diagnosis of primary cardiac neoplasia is approached through assessment of the specific location (endocardial/intracavitary, myocardial, or epicardial/pericardial) of the lesion, noting the main chamber or structure involved. The differential diagnosis can be further narrowed by assessing the morphology of the lesion, distinctive radiologic features, and associated imaging findings and correlating them with patient demographics and pertinent clinical information. Secondary involvement of the heart by neoplasia and other nonneoplastic conditions must always be considered and excluded.

Cardiac myxoma is the prototypical endocardial/intracavitary cardiac neoplasm, but it must be differentiated from the more common cardiac thrombus. Left atrial thrombi are typically located in the atrial appendage and are associated with atrial dilatation, atrial fibrillation, and mitral valvular disease (19,31,32). Echocardiographic features of left atrial thrombi include a laminated appearance, irregular or lobulated borders, microcavitations, and absence of a pedicle (110). Left ventricular thrombi occur in regions of ventricular dyskinesia or aneurysm formation, both of which result from prior myocardial infarction (5). Typically, thrombi have homogeneous attenuation on CT scans, whereas myxomas tend to be heterogeneous (32). Both thrombi and myxomas exhibit heterogeneous signal intensity on spin-echo MR images (Fig 33) and low signal intensity on GRE MR images. However, a thrombus typically does not enhance with contrast material (17,111). The differential diagnosis of a small valvular mass includes papillary fibroelastoma, vegetations, thrombus, and myxoma (5,41,43,46).

View larger version (101K): [in this window] [in a new window] [Download PPT slide]   Figure 33a.   Left ventricular thrombus in a 40-year-old woman who suffered an anterior wall myocardial infarction. The thrombus disappeared following anticoagulant therapy. (a) Contrast-enhanced chest CT scan (mediastinal window) shows a soft-tissue mass in a dilated left ventricle. (b) Axial spin-echo T1-weighted (500/30) MR image shows the heterogeneous left ventricular mass. The left ventricle is dilated and the anterior left ventricular wall is thinned secondary to the myocardial infarction.

View larger version (141K): [in this window] [in a new window] [Download PPT slide]   Figure 33b.   Left ventricular thrombus in a 40-year-old woman who suffered an anterior wall myocardial infarction. The thrombus disappeared following anticoagulant therapy. (a) Contrast-enhanced chest CT scan (mediastinal window) shows a soft-tissue mass in a dilated left ventricle. (b) Axial spin-echo T1-weighted (500/30) MR image shows the heterogeneous left ventricular mass. The left ventricle is dilated and the anterior left ventricular wall is thinned secondary to the myocardial infarction.

View larger version (128K): [in this window] [in a new window] [Download PPT slide]   Figure 34a.   Well-differentiated cardiac leiomyosarcoma in a 46-year-old man with dyspnea and medullary compression from a metastasis to the base of the skull. (a, b) Posteroanterior (a) and lateral (b) chest radiographs demonstrate left atrial enlargement (arrows), pulmonary vascular redistribution, and pulmonary interstitial edema. Note Kerley B lines of both bases. (c) Axial T1-weighted (480/21) MR image shows an aggressive left atrial mass of intermediate signal intensity that effaces the atrial lumen and extends through the posterior atrial wall and into the pulmonary veins. Note the bilateral pleural effusions.

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 34b.   Well-differentiated cardiac leiomyosarcoma in a 46-year-old man with dyspnea and medullary compression from a metastasis to the base of the skull. (a, b) Posteroanterior (a) and lateral (b) chest radiographs demonstrate left atrial enlargement (arrows), pulmonary vascular redistribution, and pulmonary interstitial edema. Note Kerley B lines of both bases. (c) Axial T1-weighted (480/21) MR image shows an aggressive left atrial mass of intermediate signal intensity that effaces the atrial lumen and extends through the posterior atrial wall and into the pulmonary veins. Note the bilateral pleural effusions.

View larger version (118K): [in this window] [in a new window] [Download PPT slide]   Figure 34c.   Well-differentiated cardiac leiomyosarcoma in a 46-year-old man with dyspnea and medullary compression from a metastasis to the base of the skull. (a, b) Posteroanterior (a) and lateral (b) chest radiographs demonstrate left atrial enlargement (arrows), pulmonary vascular redistribution, and pulmonary interstitial edema. Note Kerley B lines of both bases. (c) Axial T1-weighted (480/21) MR image shows an aggressive left atrial mass of intermediate signal intensity that effaces the atrial lumen and extends through the posterior atrial wall and into the pulmonary veins. Note the bilateral pleural effusions.

Pericardial neoplasms include teratoma, a benign tumor of infants and children, and mesothelioma, a malignant neoplasm of adults. Patients with pericardial teratoma may be discovered during prenatal US because of a thoracic mass associated with fetal hydrops. The differential diagnosis in these patients includes cystic adenomatoid malformation, extralobar pulmonary sequestration, and other intracardiac tumors including fibroma, rhabdomyoma, or hemangioma (87). However, these entities are not typically cystic. The heterogeneous, multicystic appearance, presence of calcification, and location on the right side of the heart may be distinguishing features of a pericardial teratoma. Malignant pericardial mesothelioma encases the heart and resembles secondary involvement of the pericardium by metastatic malignancy, which is much more common (112).

Cardiac lipomas are distributed throughout the heart in endocardial, myocardial, and epicardial locations (68,70). A distinction should be made between cardiac lipoma, which is a true neoplasm, and lipomatous infiltration of the interatrial septum, which is a nonneoplastic accumulation of fat cells. Lipomatous hypertrophy of the interatrial septum is associated with advancing age and obesity and can result in supraventricular arrhythmias. Microscopically, the absence of a capsule, the presence of cardiac myocytes interspersed amid the fat cells, and the presence of brown fat cells distinguish lipomatous hypertrophy from cardiac lipoma (1). CT and MR imaging demonstrate wedge-shaped or diffuse fatty thickening of the interatrial septum (113,114) (Fig 35). In contrast, lipomas are smooth-contoured, encapsulated, fatty masses. The differentiation between a lipoma and a liposarcoma is based on the irregular, multilobular morphology of the latter and the almost complete absence of identifiable fat (97).

View larger version (121K): [in this window] [in a new window] [Download PPT slide]   Figure 35.   Fatty infiltration of the interatrial septum in a 69-year-old, mildly obese woman with palpitations, dyspnea, and an atrial tachyarrhythmia. Contrast-enhanced chest CT scan (mediastinal window) demonstrates wedge-shaped fatty thickening of the interatrial septum (arrows). Note the extension of fatty tissue into the right atrium (arrowhead).

The distinction between primary and secondary cardiac neoplasms is usually easily made on clinical grounds, since almost all cardiac metastases manifest in patients with known noncardiac primary malignant neoplasms, frequently in association with widespread systemic disease. However, in some cases, especially in patients with sarcoma and lymphoma, the diagnosis of primary cardiac neoplasia may be made at autopsy through exclusion of another primary tumor elsewhere. The most common malignancies that metastasize to the heart are carcinomas of the lung and breast, followed by lymphoma and leukemia. The pericardium, including the epicardium (visceral layer of the pericardium) is by far the most commonly affected site. The myocardium can be involved through direct tumor extension from the pericardium. However, malignant melanoma may result in diffuse myocardial involvement through hematogenous spread. Only about 5% of cardiac metastases are endocardial/intracavitary lesions (1,6,115).

Summary

Primary cardiac and pericardial neoplasms are clinically significant lesions, with potential life-threatening sequelae that affect patients of all ages. Most benign neoplasms are curable with surgery, and therefore radiologic detection and characterization is critical. The early diagnosis of malignant neoplasms plays a role in palliation. In cases of lymphoma, chemotherapy may result in remission of disease. Chest radiographs are frequently abnormal, reflecting the location and extent of tumor and prompting further investigation. Echocardiography is the preferred initial imaging modality, but CT and MR imaging add very specific information in the evaluation of primary cardiac neoplasms. Tumor location, morphologic features, and tissue characteristics, including the presence of calcification, fat, fibrous tissue, hemorrhage, and cystic change, may help refine the radiologic differential diagnosis. Invasive behavior is a feature of malignant lesions. The ultimate diagnosis is based on typical pathologic features.

Footnotes

Abbreviations: GRE = gradient-recalled echo, H-E = hematoxylineosin, MFH = malignant fibrous histiocytoma

The opinions and assertions contained herein are the private views of the authors and are not to be construed as official nor as reflecting the views of the Departments of the Navy, Air Force, or Defense.

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