(Radiographics. 2000;20:1073-1103.)
© RSNA, 2000
Primary Cardiac and Pericardial Neoplasms: Radiologic-Pathologic Correlation1
Mary L. Grebenc, LCDR, MC, USNR,
Melissa L. Rosado de Christenson, Col USAF, MC,
Allen P. Burke, MD,
Curtis E. Green, MD and
Jeffrey R. Galvin, MD
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).
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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).
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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).
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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).
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Pathologic Features.—Cardiac myxomas are endocardial-based masses that do not infiltrate the underlying tissues (1). Morphologically, these lesions can be firm-surfaced and lobular (Fig 2), myxoid and gelatinous (Fig 3), or friable and irregular. The irregular tumors are those likely to form surface thrombi and embolize (Fig 4). Although the majority of tumors are attached to the endocardium by a broad-based or pedunculated stalk, approximately one-fourth are sessile. They range in size from 0.6 to 12 cm, (mean, 5.7 cm). Cut sections of tumors typically have a variegated appearance, occasionally with gritty calcified areas (1,20).
Radiologic Features.—The radiographic features of cardiac myxoma frequently reflect the location of the tumor. Patients with left atrial myxoma typically exhibit radiologic evidence of mitral valve obstruction such as left atrial enlargement and pulmonary venous hypertension with pulmonary vascular redistribution and interstitial edema, a radiographic appearance identical to that seen in mitral valve disease (Fig 5). Radiographs of patients with right atrial myxoma may demonstrate tumor calcification (Fig 6), which is pathologically more common in right than in left atrial myxomas, and cardiomegaly. Pleural effusions are occasionally observed. If the myxoma is small and does not produce obstruction, chest radiographic findings may be normal (9,20,30).
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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.
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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.
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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.
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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.
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Transthoracic echocardiography has a high sensitivity and specificity for the diagnosis of cardiac myxoma, but transesophageal echocardiography provides a more detailed evaluation, particularly in small atrial tumors. Lesions manifest as spherical masses attached to the endocardial surface with occasional internal hypoechoic areas, speckled echogenic foci, and frondlike surface projections (Fig 7). Prolapse across the atrioventricular valve during diastole may also be demonstrated. Doppler echocardiography can be used to evaluate associated valvular regurgitation or stenosis (5,19,31).
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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.
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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.
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Contrast material–enhanced chest CT usually demonstrates a well-defined spherical or ovoid intracavitary mass, typically with lobular (but occasionally smooth) contours. Tumor attenuation is lower than that of unopacified blood. Intravenous administration of contrast material helps to better define the lesion as a mass of low attenuation surrounded by the enhancing intracardiac blood (Fig 8). Heterogeneity is a common feature of myxoma and is thought to reflect hemorrhage, necrosis, cyst formation, fibrosis, calcification, or ossification (Fig 9) (32).
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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.
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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.
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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.
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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.
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At cardiac-gated MR imaging, myxomas appear as spherical or ovoid, lobular masses of heterogeneous signal intensity. In most cases, the point of attachment to the endocardial surface is accurately displayed, particularly when imaged with multiple planes and gradient-recalled echo (GRE) imaging (Fig 10). On T1-weighted images, the majority of myxomas are isointense relative to the adjacent myocardium (which has intermediate signal intensity), although they may also be hyperintense. Heterogeneous enhancement with intravenous gadolinium-based contrast material is typical and is thought to result from the cellular matrix or inflammation within the tumors, whereas nonenhancing areas likely represent cysts or necrosis (Fig 11) (17,33). Myxomatous components appear low in signal intensity on T1- and high on T2-weighted MR images, possibly owing to abundant polysaccharide-rich ground substance in the lesion. Tumor calcification manifests as low signal intensity and subacute hemorrhage displays high signal intensity on both T1- and T2-weighted images (34). Fresh hemorrhage has intermediate to low signal intensity on T1- and low signal intensity on T2-weighted images (35). Cine GRE studies are helpful in demonstrating tumor motion and prolapse across the atrioventricular valve (Fig 12). Myxomas become dark on GRE imaging, probably because of the magnetic susceptibility effects of the high iron content of these lesions (Figs 10b, 12) (33,36).
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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.
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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.
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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.
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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.
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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.
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Therapy and Prognosis.—Because of the potential life-threatening sequelae of cardiac myxoma, treatment consists of urgent surgical resection. Surgical excision is considered safe, with an excellent long-term prognosis and a low risk of recurrence (21,22,37). It is hypothesized that tumor recurrence is likely related to the development of unsuspected multifocal myxomas rather than an inadequate surgical excision, since only about one-third of resected lesions recur in situ (38). Because of the risk of recurrence, especially in the group of patients with atypical myxomas, postoperative serial follow-up imaging with echocardiography is usually employed (22,27,29,37).
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).
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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.
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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.
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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.
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Radiologic Features.—Most papillary fibroelastomas are discovered with echocardiography, which usually demonstrates a small (<1.5-cm), mobile, pedunculated, homogeneous valvular or endocardial mass, which flutters or prolapses with cardiac motion (Fig 13a). Occasionally, a stippled pattern is demonstrated on the surface of the tumor that correlates with its papillary surface projections (41,42,44). Valvular dysfunction is usually not an associated finding (41). MR imaging typically demonstrates a mass on a valve leaflet or on the endocardial surface of the affected cardiac chamber (Fig 13b). Valvular papillary fibroelastomas can result in turbulence of blood flow, which may be demonstrated with cine GRE MR imaging (43).
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).
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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).
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Pathologic Features.—Rhabdomyomas are firm, white, well-circumscribed, lobulated nodules that occur in any location in the heart but are more common in the ventricles. They are myocardial (intramural) lesions. When multiple, they can manifest as numerous miliary nodules measuring less than 1 mm in diameter ("rhabdomyomatosis"). However, tumors may also measure up to 10 cm, especially in sporadic cases, and average 3–4 cm (Fig 15) (1).
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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).
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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).
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Radiologic Features.—At echocardiography, rhabdomyomas manifest as solid hyperechoic masses usually located in the ventricular myocardium or ventricular septum and possibly protruding into and deforming the cardiac chambers (5,53). When the lesions are small and multiple, diffuse myocardial thickening is the predominant US finding (51), and this feature will also be demonstrated with MR imaging (Fig 15a). However, MR imaging may allow better definition of tumor margins and may help demonstrate individual lesions. Rhabdomyomas have signal intensity that is similar to that of the adjacent myocardium on T1-weighted images and display relatively increased signal intensity on T2-weighted images (13,54). The MR imaging assessment of these tumors can be extremely helpful when aggressive life-saving surgical resection is being considered (55). Rhabdomyomas detected with US may be missed with MR imaging and vice versa. Thus, these procedures may be complementary. In general, US better demonstrates small (<0.5-cm) or entirely intramural lesions (56).
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).
Pathologic Features.—Fibromas are round, bulging, well-circumscribed tumors located within the ventricular myocardium, often extending into or even obliterating the chamber lumen. Tumors are always single and range in size from 2 to 10 cm (Fig 17). Cut sections of cardiac fibromas reveal firm or rubbery masses, without cysts, hemorrhage, or necrosis. They may display well-circumscribed or infiltrating margins. Tumor calcification is common, may be multifocal, and is occasionally evident at pathologic examination (1,57).
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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).
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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).
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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).
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Radiologic Features.—The most frequently observed radiographic abnormality in patients with cardiac fibromas is cardiomegaly. When the tumor involves the ventricular free wall, a focal cardiac bulge or contour abnormality may also be seen. Radiographic evidence of tumor calcification is seen in approximately 25% of cases, and, when a mural location can be established, it may be a key finding to suggest cardiac fibroma as the prospective diagnosis (57,60).
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).
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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).
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Pathologic Features.—Cardiac hemangiomas can occur in any chamber. They may be predominantly intramural or endocardial-based. Intramural hemangiomas are often poorly circumscribed, spongy masses that appear variably hemorrhagic or congested. Endocardial-based hemangiomas are well-circumscribed, variably myxoid, soft masses (Fig 19) (1,63).
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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.
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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.
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Radiologic Features.—Cardiac hemangiomas are hyperechoic lesions at echocardiography, heterogeneous at unenhanced chest CT, and, in most cases, intensely enhanced at CT performed after contrast material administration. Like hepatic hemangiomas, these tumors typically demonstrate intermediate signal intensity on T1-weighted images and become hyperintense on T2-weighted images (Fig 19) (62,65,66). Coronary arteriography demonstrates the blood supply to the tumor, which is characterized by a vascular blush, particularly in the capillary and arteriovenous types of hemangiomas, which exhibit rapid blood flow. Cavernous hemangiomas have large vascular spaces with very slow flow and therefore do not typically enhance at angiography (62,65).
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).
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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.
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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.
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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.
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Radiologic Features.—The most frequent radiographic abnormality in patients with cardiac lipoma is cardiomegaly (68,70,71). A globular-shaped heart has also been described (69). Echocardiography typically demonstrates an echogenic, nonmobile mass (68,70). CT and MR imaging are useful for making a tissue-specific diagnosis based on the findings of fat attenuation (Hounsfield measurement 
-50) and signal intensity characteristics of fat (Fig 20). Lipomas appear as predominantly homogeneous masses on CT scans but may display internal soft-tissue septa or scattered strands of higher attenuation tissue. The lesion contour is typically smooth (68,69). Although these tumors do not demonstrate contrast enhancement, the use of intravenous contrast material increases the conspicuity of the mass at CT (70). Encasement of the coronary arteries may occur and can be evaluated with MR imaging. Information regarding the relationship of the mass to the coronary arteries is crucial for preoperative planning and in determining resectability (69,70).
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).
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Figure 21. Paraganglioma, microscopic features. High-power photomicrograph (original magnification, x300; H-E stain) demonstrates the classic nesting (zellballen) appearance of the paraganglial cells.
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Pathologic Features.—Cardiac paragangliomas are large, poorly circumscribed masses that typically measure 2–14 cm in greatest dimension. Most lesions are located on the epicardial surface of the base of the heart in the roof of the left atrium; less common locations include the atrial cavity, interatrial septum, and, rarely, the ventricles (1,73).
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).
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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.
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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 si | |
