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From the Archives of the AFIP

Localized Fibrous Tumors of the Pleura¹

¹ From the Department of Radiology and Nuclear Medicine, Uniformed Services University of the Health Sciences, Bethesda, Md (M.L.R.); Department of Diagnostic Imaging, Brown Medical School, Rhode Island Hospital, Providence, RI (G.F.A.); Department of Radiology, Duke University Medical Center, Durham, NC (H.P.M.); and Departments of Pulmonary and Mediastinal Pathology (T.J.F.) and Radiologic Pathology (J.R.G.), Armed Forces Institute of Pathology, Washington, DC. Received November 19, 2002; revision requested January 13, 2003 and received February 10; accepted February 13. Address correspondence to M.L.R., 7948 Creek Hollow Rd, Blacklick, OH 43004 (e-mail: rosado@insight.rr.com).

	Abstract

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Materials and Methods Results Discussion Conclusions References

 
Eighty-two localized fibrous tumors of the pleura (LFTP) were reviewed retrospectively for the clinical, pathologic, and radiologic findings. Forty-four women and 38 men ranged in age from 17 to 78 years (mean, 54.7 years). Sixty-four benign LFTP ranged in size from 2 to 30 cm (mean, 13.2 cm), and 18 malignant tumors ranged from 3 to 23 cm (mean, 14.4 cm). Forty-eight patients (60%) presented with symptoms. Radiographs of 76 patients demonstrated solitary masses occupying or extending into the inferior hemithorax (79%). Computed tomography (CT) of 78 lesions demonstrated lobular masses (83%) that formed at least one acute angle (96%) or only acute angles (65%) with the adjacent pleura. Heterogeneous lesion attenuation was documented in 88% of enhanced and in 68% of unenhanced CT scans. Contrast enhancement was common (62% of cases). Magnetic resonance (MR) imaging of 18 lesions demonstrated heterogeneous signal intensity on both T1- and T2-weighted images (78% and 83%, respectively). Multiplanar MR imaging allowed visualization of the diaphragm and documentation of an intrathoracic mass in all cases. LFTP are solitary lobular heterogeneous masses that occur in symptomatic adults and often affect the inferior hemithorax. Malignant lesions are radiologically indistinguishable from those with benign histologic characteristics. Radiographic and CT features characteristic of pleural location are typically absent.

© RSNA, 2003

Index Terms: Lung neoplasms, 66.317, 66.3254 • Pleura, neoplasms, 66.317, 66.3254

	LEARNING OBJECTIVES FOR TEST 6

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Materials and Methods Results Discussion Conclusions References

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

• Describe the clinical presentation of patients with LFTP.
  
• List the pathologic features of LFTP and address difficulties and controversies about their histologic diagnosis.
  
• Define the radiographic and cross-sectional imaging characteristics of LFTP.
  
• Discuss existing difficulties in determining the pleural origin of these intrathoracic lesions based on imaging features.
  

	Introduction

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Materials and Methods Results Discussion Conclusions References

 
Localized fibrous tumors are rare mesenchymal neoplasms that most commonly affect the pleura but have also been described in a number of other locations including the mediastinum and the lung. Extrathoracic localized fibrous tumors have been reported in the abdomen, the head and neck, and the central nervous system. Many names have been used to designate this neoplasm. The inconsistent nomenclature that appears in the published literature emphasizes controversies regarding the precursor cell for localized fibrous tumors and their variable microscopic appearance and unpredictable biologic behavior.

Patients with localized fibrous tumors of the pleura (LFTP) are typically adults who may present with symptoms related to local or systemic effects produced by the neoplasm or who may be entirely asymptomatic. Benign and malignant subtypes of LFTP are recognized. At gross examination, these are lobular soft-tissue masses, which are often described as pedunculated lesions arising from the visceral pleura. Radiologically, they are intrathoracic masses of variable sizes, which may not exhibit the classic imaging features described in extraparenchymal lesions. On cross-sectional images, they are well-defined lobular heterogeneous masses. Excision is curative in the majority of patients, although a small but significant number of lesions recur, undergo malignant transformation, or metastasize.

Although the most common primary pleural neoplasm is malignant mesothelioma, radiologists should also be able to identify the much rarer LFTP, as these two neoplasms have radically different prognoses. To help familiarize radiologists with the spectrum of radiologic features of LFTP, we review a large series of LFTP, with emphasis on the radiographic appearance of these lesions and their findings at computed tomography (CT), magnetic resonance (MR) imaging, angiography, and ultrasonography (US). We also describe the clinical presentation of patients with LFTP and the pathologic characteristics of these tumors and discuss their therapy and prognosis.

	Materials and Methods

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Materials and Methods Results Discussion Conclusions References

 
A retrospective review of 101 cases of localized fibrous tumors referred to the Pulmonary and Mediastinal Section of the Department of Radiologic Pathology at the Armed Forces Institute of Pathology (AFIP) between 1987 and 2001 was performed. Ten multifocal or recurrent LFTP and nine extrapleural localized fibrous tumors occurring in the mediastinum (n = 6) and in the lung (n = 3) were excluded. The remaining 82 LFTP form the basis of this review. Seventy-six lesions were evaluated with chest radiography, 78 with chest CT, 18 with MR imaging, 10 with angiography, and nine with US. Fifty-five patients were imaged with chest radiography and CT; 17 with chest radiography, CT, and MR imaging; and one with chest radiography and MR imaging. Six patients were evaluated only with CT, and three with only chest radiography.

For 80 patients, detailed clinical histories were available and were reviewed for age, gender, and clinical presentation. Surgical and pathology reports were reviewed to determine tumor size, location, pleural surface of origin, presence or absence of a pedicle, as well as gross and microscopic findings. Results of needle biopsies, when performed, were also noted. The diagnosis of localized fibrous tumor was confirmed in every case through the microscopic evaluation of glass slides prepared from the resected tissues and reviewed by an experienced thoracic pathologist in the Department of Pulmonary and Mediastinal Pathology at the AFIP. The lesions were classified as benign or malignant based on established histologic criteria, particularly the presence of more than four mitotic figures per 10 high-power fields.

All chest radiographs and CT studies were reviewed by two thoracic radiologists (M.L.R., G.F.A.), and MR imaging studies were reviewed by three thoracic radiologists (M.L.R., G.F.A., H.P.M.). Findings were recorded by consensus. Chest radiographs were evaluated to determine lesion size and location within the thorax as well as border characteristics and presence or absence of associated findings including pleural effusion and mass effect.

CT studies were performed at multiple institutions with a variety of scanners and variable scanning techniques. Sixty-six studies were performed after the administration of intravenous contrast material, and 25 were performed without contrast material (13 of these studies were performed before and after intravenous contrast material administration). Lesions were evaluated to determine location, mobility within the thorax, border characteristics, attenuation, presence or absence of calcification, and patterns of contrast enhancement.

MR imaging studies were performed on a variety of MR imaging equipment, with various combinations of axial, coronal, and sagittal planes. Fifteen lesions were imaged with T1-weighted and T2-weighted or cine gradient recalled echo sequences, and three lesions were imaged with T1-weighted sequences only. Six lesions were imaged before and after administration of intravenous gadolinium. All lesions were evaluated to determine morphologic features, signal intensity characteristics, and patterns of enhancement and to exclude involvement of adjacent structures.

	Results

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Patients and Clinical Presentation
There were 44 women and 38 men who ranged in age from 17 to 78 years (mean, 54.7 years). Sixty-four patients had benign LFTP (35 women, 29 men), and 18 had malignant tumors (nine women, nine men). The patients with benign LFTP ranged in age from 25 to 78 years (mean age, 55.9 years), and those with malignant LFTP ranged in age from 17 to 75 years (mean age, 52.5 years). Eighty-four percent of benign and 78% of malignant LFTP affected patients in the fifth through eighth decades of life. Clinical data (available in 80 of 82 patients) are presented in Table 1.

View larger version (156K): [in this window] [in a new window] [Download PPT slide]   Figure 1.  Benign LFTP. Photograph of a resected, ovoid LFTP, which arose from the parietal pleura, shows prominent blood vessels over the thin serosal lining of the tumor. The tumor was excised en bloc with a portion of the adjacent chest wall.

View larger version (131K): [in this window] [in a new window] [Download PPT slide]   Figure 2.  Benign LFTP. Intraoperative photograph shows a pedunculated LFTP, which arises from the visceral pleura. The surgical forceps hold the adjacent partially collapsed lung.

View larger version (141K): [in this window] [in a new window] [Download PPT slide]   Figure 3.  Benign LFTP. Photograph of a cut section of a pedunculated LFTP demonstrates an ovoid lobular mass with a thin pedicle (arrow) by which it was attached to the visceral pleura. Note the firm, yellow-tan appearance of the tumor.

View larger version (162K): [in this window] [in a new window] [Download PPT slide]   Figure 4.  Benign LFTP. Photograph of a benign LFTP demonstrates a spherical lobular mass. Note the site of prior broad attachment (arrows) of the lesion to the parietal pleura.

Pathologic Findings
Needle biopsies were performed in 27 lesions (22 benign, five malignant). The diagnosis of LFTP was established in seven benign and in one malignant LFTP based on the microscopic examination of the biopsy specimens. The remaining biopsies were inconclusive. There were 64 benign and 18 malignant LFTP. Pathology reports were available in 81 cases. Forty-nine LFTP (60%) were located in the right hemithorax, and 33 (40%) in the left. Benign lesions ranged in size from 2 to 30 cm (average size, 13.2 cm), and malignant lesions ranged in size from 3 to 23 cm (average size, 14.4 cm). Macroscopic descriptions of 63 benign LFTP noted gross evidence of hemorrhage in 27 (43%), cystic change in 14 (22%), and necrosis in three (5%) (Fig 5). Seven malignant LFTP (39%) exhibited hemorrhage, four (22%) had necrosis, and cystic change was found in three (17%).

View larger version (117K): [in this window] [in a new window] [Download PPT slide]   Figure 5.  Benign LFTP. Photograph of a cut section of a benign LFTP demonstrates an ovoid lobular mass with extensive internal hemorrhage and necrosis.

View larger version (155K): [in this window] [in a new window] [Download PPT slide]   Figure 6a.  Benign LFTP in an asymptomatic 29-year-old woman. Posteroanterior (PA) (a) and lateral (b) chest radiographs demonstrate an ovoid, slightly lobular mass in the left inferior hemithorax that abuts the left hemidiaphragm.

View larger version (134K): [in this window] [in a new window] [Download PPT slide]   Figure 6b.  Benign LFTP in an asymptomatic 29-year-old woman. Posteroanterior (PA) (a) and lateral (b) chest radiographs demonstrate an ovoid, slightly lobular mass in the left inferior hemithorax that abuts the left hemidiaphragm.

View larger version (145K): [in this window] [in a new window] [Download PPT slide]   Figure 7a.  Benign LFTP in a 62-year-old woman with right-sided chest pain. PA (a) and lateral (b) chest radiographs demonstrate a rounded well-defined mass of the right inferior hemithorax that conforms to the shape of the diaphragm and mimics diaphragmatic elevation. The LFTP was discovered at abdominal CT.

View larger version (120K): [in this window] [in a new window] [Download PPT slide]   Figure 7b.  Benign LFTP in a 62-year-old woman with right-sided chest pain. PA (a) and lateral (b) chest radiographs demonstrate a rounded well-defined mass of the right inferior hemithorax that conforms to the shape of the diaphragm and mimics diaphragmatic elevation. The LFTP was discovered at abdominal CT.

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 8a.  Benign LFTP in a 73-year-old woman with dyspnea, weight loss, and hypoglycemia. (a, b) PA (a) and lateral (b) chest radiographs demonstrate a large mass that occupies more than half of the right hemithorax. The superior border of the lesion is lobular and well defined. (c) Photograph of a cut section of the resected mass demonstrates a lobular contour and a whorled nodular fibrous appearance. Scale is in centimeters.

View larger version (116K): [in this window] [in a new window] [Download PPT slide]   Figure 8b.  Benign LFTP in a 73-year-old woman with dyspnea, weight loss, and hypoglycemia. (a, b) PA (a) and lateral (b) chest radiographs demonstrate a large mass that occupies more than half of the right hemithorax. The superior border of the lesion is lobular and well defined. (c) Photograph of a cut section of the resected mass demonstrates a lobular contour and a whorled nodular fibrous appearance. Scale is in centimeters.

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 8c.  Benign LFTP in a 73-year-old woman with dyspnea, weight loss, and hypoglycemia. (a, b) PA (a) and lateral (b) chest radiographs demonstrate a large mass that occupies more than half of the right hemithorax. The superior border of the lesion is lobular and well defined. (c) Photograph of a cut section of the resected mass demonstrates a lobular contour and a whorled nodular fibrous appearance. Scale is in centimeters.

View larger version (139K): [in this window] [in a new window] [Download PPT slide]   Figure 9a.  Benign LFTP in an asymptomatic 54-year-old man. (a, b) PA (a) and lateral (b) chest radiographs demonstrate an ovoid mass in the left hemithorax. The inferior border of the lesion is well defined, but its superior border is ill defined (a). The lesion is aligned along the course of the major fissure on the lateral radiograph (b). (c, d) PA (c) and lateral (d) chest radiographs obtained 6 years later demonstrate interval growth of the lesion and a change in its position within the thorax that confirms its pleural location. (e) Contrast-enhanced chest CT scan (lung window) shows the superior border of the lesion, its extension into the fissure, and a pedicle (arrow) that connected the mass to the fissural visceral pleura. (f) Contrast-enhanced chest CT scan (mediastinal window) demonstrates the heterogeneously enhancing lobular mass, which forms obtuse and acute angles with the adjacent pleura. Note associated ipsilateral pleural thickening or fluid.

View larger version (162K): [in this window] [in a new window] [Download PPT slide]   Figure 9b.  Benign LFTP in an asymptomatic 54-year-old man. (a, b) PA (a) and lateral (b) chest radiographs demonstrate an ovoid mass in the left hemithorax. The inferior border of the lesion is well defined, but its superior border is ill defined (a). The lesion is aligned along the course of the major fissure on the lateral radiograph (b). (c, d) PA (c) and lateral (d) chest radiographs obtained 6 years later demonstrate interval growth of the lesion and a change in its position within the thorax that confirms its pleural location. (e) Contrast-enhanced chest CT scan (lung window) shows the superior border of the lesion, its extension into the fissure, and a pedicle (arrow) that connected the mass to the fissural visceral pleura. (f) Contrast-enhanced chest CT scan (mediastinal window) demonstrates the heterogeneously enhancing lobular mass, which forms obtuse and acute angles with the adjacent pleura. Note associated ipsilateral pleural thickening or fluid.

View larger version (143K): [in this window] [in a new window] [Download PPT slide]   Figure 9c.  Benign LFTP in an asymptomatic 54-year-old man. (a, b) PA (a) and lateral (b) chest radiographs demonstrate an ovoid mass in the left hemithorax. The inferior border of the lesion is well defined, but its superior border is ill defined (a). The lesion is aligned along the course of the major fissure on the lateral radiograph (b). (c, d) PA (c) and lateral (d) chest radiographs obtained 6 years later demonstrate interval growth of the lesion and a change in its position within the thorax that confirms its pleural location. (e) Contrast-enhanced chest CT scan (lung window) shows the superior border of the lesion, its extension into the fissure, and a pedicle (arrow) that connected the mass to the fissural visceral pleura. (f) Contrast-enhanced chest CT scan (mediastinal window) demonstrates the heterogeneously enhancing lobular mass, which forms obtuse and acute angles with the adjacent pleura. Note associated ipsilateral pleural thickening or fluid.

View larger version (156K): [in this window] [in a new window] [Download PPT slide]   Figure 9d.  Benign LFTP in an asymptomatic 54-year-old man. (a, b) PA (a) and lateral (b) chest radiographs demonstrate an ovoid mass in the left hemithorax. The inferior border of the lesion is well defined, but its superior border is ill defined (a). The lesion is aligned along the course of the major fissure on the lateral radiograph (b). (c, d) PA (c) and lateral (d) chest radiographs obtained 6 years later demonstrate interval growth of the lesion and a change in its position within the thorax that confirms its pleural location. (e) Contrast-enhanced chest CT scan (lung window) shows the superior border of the lesion, its extension into the fissure, and a pedicle (arrow) that connected the mass to the fissural visceral pleura. (f) Contrast-enhanced chest CT scan (mediastinal window) demonstrates the heterogeneously enhancing lobular mass, which forms obtuse and acute angles with the adjacent pleura. Note associated ipsilateral pleural thickening or fluid.

View larger version (152K): [in this window] [in a new window] [Download PPT slide]   Figure 9e.  Benign LFTP in an asymptomatic 54-year-old man. (a, b) PA (a) and lateral (b) chest radiographs demonstrate an ovoid mass in the left hemithorax. The inferior border of the lesion is well defined, but its superior border is ill defined (a). The lesion is aligned along the course of the major fissure on the lateral radiograph (b). (c, d) PA (c) and lateral (d) chest radiographs obtained 6 years later demonstrate interval growth of the lesion and a change in its position within the thorax that confirms its pleural location. (e) Contrast-enhanced chest CT scan (lung window) shows the superior border of the lesion, its extension into the fissure, and a pedicle (arrow) that connected the mass to the fissural visceral pleura. (f) Contrast-enhanced chest CT scan (mediastinal window) demonstrates the heterogeneously enhancing lobular mass, which forms obtuse and acute angles with the adjacent pleura. Note associated ipsilateral pleural thickening or fluid.

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 9f.  Benign LFTP in an asymptomatic 54-year-old man. (a, b) PA (a) and lateral (b) chest radiographs demonstrate an ovoid mass in the left hemithorax. The inferior border of the lesion is well defined, but its superior border is ill defined (a). The lesion is aligned along the course of the major fissure on the lateral radiograph (b). (c, d) PA (c) and lateral (d) chest radiographs obtained 6 years later demonstrate interval growth of the lesion and a change in its position within the thorax that confirms its pleural location. (e) Contrast-enhanced chest CT scan (lung window) shows the superior border of the lesion, its extension into the fissure, and a pedicle (arrow) that connected the mass to the fissural visceral pleura. (f) Contrast-enhanced chest CT scan (mediastinal window) demonstrates the heterogeneously enhancing lobular mass, which forms obtuse and acute angles with the adjacent pleura. Note associated ipsilateral pleural thickening or fluid.

View larger version (164K): [in this window] [in a new window] [Download PPT slide]   Figure 10a.  Benign LFTP in a 72-year-old man with dyspnea. (a, b) PA (a) and lateral (b) chest radiographs demonstrate an enormous mass that occupies almost the entire right hemithorax and produces mass effect on the mediastinum. Note the well-defined lobular superior border of the lesion and the right pleural effusion. (c) Contrast-enhanced chest CT scan (mediastinal window) demonstrates the large heterogeneously enhancing mass in the right hemithorax, which produces mass effect on the mediastinum as well as atelectasis of the adjacent lung. Note geographic areas of low attenuation within the lesion.

View larger version (144K): [in this window] [in a new window] [Download PPT slide]   Figure 10b.  Benign LFTP in a 72-year-old man with dyspnea. (a, b) PA (a) and lateral (b) chest radiographs demonstrate an enormous mass that occupies almost the entire right hemithorax and produces mass effect on the mediastinum. Note the well-defined lobular superior border of the lesion and the right pleural effusion. (c) Contrast-enhanced chest CT scan (mediastinal window) demonstrates the large heterogeneously enhancing mass in the right hemithorax, which produces mass effect on the mediastinum as well as atelectasis of the adjacent lung. Note geographic areas of low attenuation within the lesion.

View larger version (140K): [in this window] [in a new window] [Download PPT slide]   Figure 10c.  Benign LFTP in a 72-year-old man with dyspnea. (a, b) PA (a) and lateral (b) chest radiographs demonstrate an enormous mass that occupies almost the entire right hemithorax and produces mass effect on the mediastinum. Note the well-defined lobular superior border of the lesion and the right pleural effusion. (c) Contrast-enhanced chest CT scan (mediastinal window) demonstrates the large heterogeneously enhancing mass in the right hemithorax, which produces mass effect on the mediastinum as well as atelectasis of the adjacent lung. Note geographic areas of low attenuation within the lesion.

View larger version (136K): [in this window] [in a new window] [Download PPT slide]   Figure 11a.  Benign LFTP in an asymptomatic 39-year-old man. Unenhanced chest CT scans (mediastinal window) demonstrate a soft-tissue mass of the left inferior hemithorax with well-defined lobular borders. The mass forms acute angles with the adjacent pleural surface and contains a geographic area of low attenuation (a) and multifocal coarse calcifications (b).

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 11b.  Benign LFTP in an asymptomatic 39-year-old man. Unenhanced chest CT scans (mediastinal window) demonstrate a soft-tissue mass of the left inferior hemithorax with well-defined lobular borders. The mass forms acute angles with the adjacent pleural surface and contains a geographic area of low attenuation (a) and multifocal coarse calcifications (b).

View larger version (160K): [in this window] [in a new window] [Download PPT slide]   Figure 12a.  Malignant LFTP in a 30-year-old man with chest pain. (a) PA chest radiograph demonstrates a well-marginated rounded mass in the right paravertebral inferior hemithorax. (b) Unenhanced chest CT scan (mediastinal window) demonstrates a well-defined heterogeneous mass with focal areas of low attenuation and subtle punctate calcification. Note that the lesion forms acute angles with the adjacent pleura. (c) Selective angiogram demonstrates exuberant tumor vascularity. (d) Photograph of a cut section of the resected gross specimen demonstrates a heterogeneous spherical mass with extensive necrosis, hemorrhage,and cystic change.

View larger version (134K): [in this window] [in a new window] [Download PPT slide]   Figure 12b.  Malignant LFTP in a 30-year-old man with chest pain. (a) PA chest radiograph demonstrates a well-marginated rounded mass in the right paravertebral inferior hemithorax. (b) Unenhanced chest CT scan (mediastinal window) demonstrates a well-defined heterogeneous mass with focal areas of low attenuation and subtle punctate calcification. Note that the lesion forms acute angles with the adjacent pleura. (c) Selective angiogram demonstrates exuberant tumor vascularity. (d) Photograph of a cut section of the resected gross specimen demonstrates a heterogeneous spherical mass with extensive necrosis, hemorrhage,and cystic change.

View larger version (141K): [in this window] [in a new window] [Download PPT slide]   Figure 12c.  Malignant LFTP in a 30-year-old man with chest pain. (a) PA chest radiograph demonstrates a well-marginated rounded mass in the right paravertebral inferior hemithorax. (b) Unenhanced chest CT scan (mediastinal window) demonstrates a well-defined heterogeneous mass with focal areas of low attenuation and subtle punctate calcification. Note that the lesion forms acute angles with the adjacent pleura. (c) Selective angiogram demonstrates exuberant tumor vascularity. (d) Photograph of a cut section of the resected gross specimen demonstrates a heterogeneous spherical mass with extensive necrosis, hemorrhage,and cystic change.

View larger version (121K): [in this window] [in a new window] [Download PPT slide]   Figure 12d.  Malignant LFTP in a 30-year-old man with chest pain. (a) PA chest radiograph demonstrates a well-marginated rounded mass in the right paravertebral inferior hemithorax. (b) Unenhanced chest CT scan (mediastinal window) demonstrates a well-defined heterogeneous mass with focal areas of low attenuation and subtle punctate calcification. Note that the lesion forms acute angles with the adjacent pleura. (c) Selective angiogram demonstrates exuberant tumor vascularity. (d) Photograph of a cut section of the resected gross specimen demonstrates a heterogeneous spherical mass with extensive necrosis, hemorrhage,and cystic change.

View larger version (157K): [in this window] [in a new window] [Download PPT slide]   Figure 13.  Benign LFTP in an asymptomatic 71-year-old woman. Targeted unenhanced chest CT scan (mediastinal window) demonstrates a homogeneous ovoid lobular soft-tissue mass abutting the descending aorta. Although the lesion forms acute angles with the pleura, a smoothly tapering margin (arrow) is also seen.

View larger version (148K): [in this window] [in a new window] [Download PPT slide]   Figure 14.  Benign LFTP in a 54-year-old woman with dyspnea. Contrast-enhanced chest CT scan (mediastinal window) demonstrates a heterogeneously enhancing soft-tissue mass of the left inferior hemithorax with internal focal and linear areas of low attenuation.

View larger version (161K): [in this window] [in a new window] [Download PPT slide]   Figure 15.  Benign LFTP in a 54-year-old woman with chest pain and dyspnea. Contrast-enhanced chest CT scan (mediastinal window) demonstrates an enormous heterogeneously enhancing soft-tissue mass in the right hemithorax that produces mass effect on the heart. Note the serpiginous branching linear areas of enhancement consistent with intralesional vessels and the geographic and linear areas of low attenuation within the lesion. Enhancing portions of the lesion have a nodular pattern of attenuation.

View larger version (175K): [in this window] [in a new window] [Download PPT slide]   Figure 16a.  Benign LFTP in an asymptomatic 62-year-old man. (a) Contrast-enhanced chest CT scan (mediastinal window) demonstrates a lobular heterogeneous soft-tissue mass with geographic and focal areas of low attenuation. Note that the lesion forms acute angles with the adjacent pleura. (b) Photograph of a cut section of the gross specimen demonstrates a well-circumscribed lobular mass with a focal area of necrosis that corresponds to the low-attenuation area seen at CT.

View larger version (127K): [in this window] [in a new window] [Download PPT slide]   Figure 16b.  Benign LFTP in an asymptomatic 62-year-old man. (a) Contrast-enhanced chest CT scan (mediastinal window) demonstrates a lobular heterogeneous soft-tissue mass with geographic and focal areas of low attenuation. Note that the lesion forms acute angles with the adjacent pleura. (b) Photograph of a cut section of the gross specimen demonstrates a well-circumscribed lobular mass with a focal area of necrosis that corresponds to the low-attenuation area seen at CT.

View larger version (144K): [in this window] [in a new window] [Download PPT slide]   Figure 17a.  Benign LFTP in a 77-year-old man with dyspnea, cough, and weight loss. (a) Contrast-enhanced chest CT scan (mediastinal window) demonstrates a large heterogeneous soft-tissue mass of lobular borders with a large ovoid area of focal low attenuation as well as smaller foci of low attenuation. (b) Sagittal US scan through the left upper quadrant allows visualization of the spleen and diaphragm as well as the supradiaphragmatic hypoechoic LFTP. (c) Photograph of a cut section of the gross specimen demonstrates a large lobular heterogeneous soft-tissue mass with a nodular cut surface as well as areas of necrosis (arrow) and hemorrhage (arrowhead).

View larger version (139K): [in this window] [in a new window] [Download PPT slide]   Figure 17b.  Benign LFTP in a 77-year-old man with dyspnea, cough, and weight loss. (a) Contrast-enhanced chest CT scan (mediastinal window) demonstrates a large heterogeneous soft-tissue mass of lobular borders with a large ovoid area of focal low attenuation as well as smaller foci of low attenuation. (b) Sagittal US scan through the left upper quadrant allows visualization of the spleen and diaphragm as well as the supradiaphragmatic hypoechoic LFTP. (c) Photograph of a cut section of the gross specimen demonstrates a large lobular heterogeneous soft-tissue mass with a nodular cut surface as well as areas of necrosis (arrow) and hemorrhage (arrowhead).

View larger version (130K): [in this window] [in a new window] [Download PPT slide]   Figure 17c.  Benign LFTP in a 77-year-old man with dyspnea, cough, and weight loss. (a) Contrast-enhanced chest CT scan (mediastinal window) demonstrates a large heterogeneous soft-tissue mass of lobular borders with a large ovoid area of focal low attenuation as well as smaller foci of low attenuation. (b) Sagittal US scan through the left upper quadrant allows visualization of the spleen and diaphragm as well as the supradiaphragmatic hypoechoic LFTP. (c) Photograph of a cut section of the gross specimen demonstrates a large lobular heterogeneous soft-tissue mass with a nodular cut surface as well as areas of necrosis (arrow) and hemorrhage (arrowhead).

View larger version (151K): [in this window] [in a new window] [Download PPT slide]   Figure 18a.  Benign LFTP in an asymptomatic 68-year-old man. (a) Coronal T1-weighted MR image demonstrates a large lobular heterogeneous mass of intermediate signal intensity with linear areas of high signal intensity. Note mass effect on the ipsilateral hemidiaphragm and mediastinum. (b) Coronal T1-weighted MR image obtained after intravenous administration of gadolinium demonstrates heterogeneous patchy multifocal enhancement within the lesion.

View larger version (165K): [in this window] [in a new window] [Download PPT slide]   Figure 18b.  Benign LFTP in an asymptomatic 68-year-old man. (a) Coronal T1-weighted MR image demonstrates a large lobular heterogeneous mass of intermediate signal intensity with linear areas of high signal intensity. Note mass effect on the ipsilateral hemidiaphragm and mediastinum. (b) Coronal T1-weighted MR image obtained after intravenous administration of gadolinium demonstrates heterogeneous patchy multifocal enhancement within the lesion.

View larger version (174K): [in this window] [in a new window] [Download PPT slide]   Figure 19a.  Benign LFTP in a 48-year-old man with chest pain. (a) Sagittal T1-weighted MR image demonstrates a lobular ovoid mass of intermediate signal intensity located in the right inferior hemithorax. Note mass effect on the liver and focal chest wall invasion. (b) Sagittal T2-weighted MR image at the same level demonstrates heterogeneous high signal intensity with flow void areas within the lesion that represent vessels and intrinsic low-signal-intensity septa (arrow).

View larger version (187K): [in this window] [in a new window] [Download PPT slide]   Figure 19b.  Benign LFTP in a 48-year-old man with chest pain. (a) Sagittal T1-weighted MR image demonstrates a lobular ovoid mass of intermediate signal intensity located in the right inferior hemithorax. Note mass effect on the liver and focal chest wall invasion. (b) Sagittal T2-weighted MR image at the same level demonstrates heterogeneous high signal intensity with flow void areas within the lesion that represent vessels and intrinsic low-signal-intensity septa (arrow).

View larger version (153K): [in this window] [in a new window] [Download PPT slide]   Figure 20a.  Malignant LFTP in a 53-year-old woman with abdominal pain. (a) Axial T1-weighted MR image shows a mass of intermediate to low signal intensity in the right diaphragmatic region, which produces mass effect on the diaphragm and indents the liver. (b) Sagittal T1-weighted MR image obtained after intravenous administration of gadolinium shows heterogeneous contrast enhancement and extension through the diaphragm. Note that a large portion of the mass is intrahepatic and thus a tumor of liver origin would have to be considered. Diaphragm invasion was documented at surgery.

View larger version (172K): [in this window] [in a new window] [Download PPT slide]   Figure 20b.  Malignant LFTP in a 53-year-old woman with abdominal pain. (a) Axial T1-weighted MR image shows a mass of intermediate to low signal intensity in the right diaphragmatic region, which produces mass effect on the diaphragm and indents the liver. (b) Sagittal T1-weighted MR image obtained after intravenous administration of gadolinium shows heterogeneous contrast enhancement and extension through the diaphragm. Note that a large portion of the mass is intrahepatic and thus a tumor of liver origin would have to be considered. Diaphragm invasion was documented at surgery.

Ultrasonography.— Nine benign LFTP were imaged with US. Six masses (67%) were heterogeneous and exhibited hypoechoic and hyperechoic areas but no cysts or calcification. US visualization of the diaphragm was documented in five cases, established the intrathoracic location of the lesion in all, and showed mass effect without invasion in three (Fig 17b).

Radiologic Reports.— A review of the radiologic reports generated at the time the lesions were originally imaged (n = 80) showed that the diagnosis of LFTP was not mentioned in the preoperative differential diagnosis for 43 (54%) cases (33 benign, 10 malignant). The specific diagnosis of LFTP was included in the differential diagnosis for 21 (26%) lesions (15 benign, six malignant), and 16 (20%) lesions (14 benign, two malignant) were characterized as pleural in location.

	Discussion

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Materials and Methods Results Discussion Conclusions References

 
Primary pleural neoplasms are rare and represent less than 5% of all pleural neoplasia. The most common primary pleural neoplasm is malignant mesothelioma, a highly aggressive malignancy that is associated with asbestos exposure. Malignant mesothelioma is characterized by diffuse circumferential pleural involvement and a poor prognosis (1). The first report of a primary pleural neoplasm dates back to 1767 and is attributed to Lieutaud (2). Wagner published the first microscopic description of a primary diffuse pleural neoplasm in 1870 and proposed that the tumor was derived from the endothelium of the pleural lymphatics (3,4). In 1931, Klemperer and Rabin classified primary pleural neoplasms as localized and diffuse types and proposed that a submesothelial mesenchymal cell was the cell of origin for the localized type (5). LFTP are rare neoplasms; only over 600 cases have been reported in the scientific literature (6). In a 1978 review of 60 cases of LFTP, Okike and colleagues (7) reported a prevalence of only 2.8 cases per 100,000 registrations at their institution, the Mayo Clinic.

Pathogenesis
Different theories about the cell of origin for LFTP have been proposed and probably account for the varied nomenclature used to designate this rare neoplasm. Localized mesothelioma, fibrous mesothelioma, benign fibrous mesothelioma, localized fibrous mesothelioma, benign mesothelioma, benign localized mesothelioma, fibrosing mesothelioma, and mesothelial fibroma represent nomenclature that alludes to early theories supporting a mesothelial cell of origin (3,8–12). Terms such as subpleural fibroma, submesothelial fibroma, and submesothelioma suggest a submesothelial precursor cell (3,10). Pleural fibroma, benign pleural fibroma, pleural fibromyxoma, solitary fibrous tumor of the pleura, and localized fibrous tumor of the serosal cavities are additional terms that have been used to designate these lesions (10,11,13). The currently accepted nomenclature is localized fibrous tumor of the pleura, and a derivation from submesothelial mesenchymal cells with a fibroblastic differentiation is generally acknowledged (11).

Lesions of similar histologic characteristics have been reported in extrapleural thoracic locations, including the mediastinum, lung, pericardium, and heart (14–16). Yousem and Flynn (17) described three intrapulmonary localized fibrous tumors and suggested a common origin for this subset of lesions from tissues in the interlobular septa. Localized fibrous tumors have also been reported in the abdomen (liver, peritoneum, and retroperitoneum) and in the meninges, orbit, thyroid, salivary gland, and the soft tissues including the breast (15,16,18). It has been suggested that the upper respiratory tract may be a preferred extrathoracic location, with reports of localized fibrous tumors arising in the nose, paranasal sinuses, parapharyngeal tissues, nasopharynx and epiglottis (15,19).

Clinical Characteristics
LFTP affect male and female patients, with a slight female predominance reported in some studies (3). Women represented 55% of patients with benign LFTP and 50% of patients with malignant LFTP in our series. Affected patients display a wide age range (5–87 years), with the majority of cases reported in the 6th and 7th decades of life and a reported mean age of 50–57 years (3,20,21). Although 83% of the patients in our series were older than 40 years, only 41% were in the 6th and 7th decades of life. LFTP are not thought to be related to exposure to cigarette smoke, asbestos, or other environmental pollutants (22,23). However, there are at least two case reports of patients with LFTP who were exposed to asbestos and one of a patient who developed a LFTP following thoracic irradiation for the treatment of a chest wall keloid (24,25).

Up to 50% of patients with LFTP, particularly those with small neoplasms, may be entirely asymptomatic, and the tumor is discovered incidentally because of radiographs obtained for other reasons (3,21,26). When signs and symptoms (particularly digital clubbing and hypertrophic osteoarthropathy) are present, they are usually associated with larger tumors and may occur more frequently in association with malignant subtypes of LFTP (7,27). Interestingly, the average size of LFTP that affected asymptomatic individuals in our series was 10.5 cm, whereas the average size of those that occurred in symptomatic patients was 16.6 cm. Studies of patients with LFTP published from 1942 to 1972 reported that 72% of patients were symptomatic at presentation, whereas studies published between 1973 and 1980 reported symptoms in only 54% of patients. This decrease in the prevalence of symptoms in patients with LFTP may relate to more widespread imaging of asymptomatic populations and the resultant detection of a larger number of incidental tumors (3).

Reported symptoms are similar to those exhibited by our patients and include respiratory and thoracic complaints such as cough, dyspnea, hemoptysis, chest pain, chest heaviness, and the sensation of a mass moving within the chest (3,21) (Table 1). Abdominal pain has been reported in patients with supradiaphragmatic tumors (28). Systemic complaints may occur and include chills, sweats, weakness, and weight loss (3). Paraneoplastic syndromes such as hypoglycemia, digital clubbing, and hypertrophic osteoarthropathy are uncommon, but when they are associated with an intrathoracic mass they may suggest the diagnosis of LFTP (4,29,30). These systemic effects typically occur with large tumors and generally resolve after excision of the neoplasms but may recur with subsequent tumor recurrences (12,30–32). Non–islet cell tumor hypoglycemia has been described in association with both epithelial and mesenchymal neoplasms, including LFTP (30,32–34). Many theories have been proposed to explain this phenomenon, including increased glucose consumption by the tumor; proliferation of insulin receptors; impaired growth hormone counter-regulatory responses to hypoglycemia; and tumor secretion of insulin-like substances, such as insulin-like growth factor 2 (IGF-2) and a high molecular weight ("big") IGF-2 (4,30,32,35–38). In some patients, hypoglycemic coma may be the presenting manifestation of a LFTP (34). Hypertrophic osteoarthropathy may relate to hyaluronic acid production and its osteolytic effects and is reported in 17%–35% of cases (4,8,37,39). Although hypertrophic osteoarthropathy has been described in cases of lung carcinoma, malignant pleural mesothelioma, and even empyema and other thoracic infections, LFTP may produce it more commonly (4). Interestingly, none of our patients presented with hypertrophic osteoarthropathy.

Gross Features
LFTP are typically solitary lesions with rare occurrences of conglomerate or multifocal masses. Sixty-six percent to 70% of localized fibrous tumors arise from the visceral pleura, and nearly half are pedunculated, with the vascular supply to the tumor contained within the pedicle (21,40) (Figs 2, 3). Although a pedicle was present in 49% of our cases, 55% of the lesions arose from the parietal pleural surface (Fig 1). This discrepancy may relate to selection bias, because our cases were collected through consultation for second-opinion diagnosis or through case contributions by residents attending AFIP courses, and only cases with imaging studies were included. The AFIP series published by England and colleagues (21), based on a larger number of cases (n = 223) submitted to the Institute before 1988, documented origin of LFTP from the visceral pleura in 66% of cases. Adhesions to the adjacent pleural surfaces and pericardium are common (3,21). LFTP are usually well-circumscribed masses with lobular or smooth external surfaces and a thin, glistening translucent serosa through which a network of prominent blood vessels may be seen (Fig 1) (40). The cut surface is firm, pink-white or yellow-tan and often exhibits a whorled or nodular pattern (Figs 3, 8c). Areas of necrosis, hemorrhage, or cystic degeneration may be evident, particularly in large or malignant lesions (Figs 5, 12d, 16b, 17c).

Histologic Characteristics
England and colleagues (21) proposed that LFTP originated from the submesothelial connective tissues and suggested a primitive multipotential cell of mesenchymal differentiation as the cell of origin. At histologic analysis, localized fibrous tumors appear as low-grade neoplasms of variable cellularity. The tumor cells are ovoid to spindle-shaped with round to oval nuclei, an evenly distributed fine chromatin, inconspicuous nucleoli, and bipolar faintly eosinophilic cytoplasm with indistinct cell borders (Fig 21). Nuclear pleomorphism is minimal and mitoses are usually rare or absent. Cellularity is variable and is inversely related to collagen content (21). Collagen ranges from wispy fibrils surrounding tumor cells in hypercellular areas to thick, dense, wirelike or "ropy" collagen forming sclerotic zones in hypocellular areas (Figs 21, 22). Tumors are usually well vascularized with vessels of varying sizes (23). Degenerative features including myxoid change and degeneration of collagen may occur (41). Microscopic examination reveals a variety of architectural patterns, with the most frequent being an intermingling of tumor cells and collagen in a random fashion, the so-called patternless pattern (Fig 21a) (41). The second most common pattern is characterized by hypercellular zones that contain a network of open anastomosing or staghorn-shaped vessels that result in a hemangiopericytoma-like appearance (Fig 23). Less frequently, localized fibrous tumors may adopt angiofibroma-like (numerous small and medium-sized vessels), fibrosarcoma-like (herringbone), monophasic variant of synovial sarcoma–like (densely cellular fascicles), and neural (wavy nuclei, palisading) patterns (41).

View larger version (188K): [in this window] [in a new window] [Download PPT slide]   Figure 21a.  Benign LFTP. (a, b) High-power (original magnification, x400) (a) and intermediate-power (original magnification, x200) (b) photomicrographs (hematoxylin-eosin [H-E] stain) demonstrate the bland, low-grade appearance of spindle-shaped tumor cells (a) that are arranged in a haphazard or so-called patternless pattern (b), the classic appearance of localized fibrous tumors. (c, d) High-power photomicrographs (original magnification, x400; H-E stain) of the same neoplasm demonstrate the variable cellularity characteristic of localized fibrous tumors. A hypercellular area (c) is composed of abundant spindle-shaped cells with a paucity of collagen fibers, whereas a hypocellular area (d) demonstrates abundant collagen (*) between tumor cells.

View larger version (189K): [in this window] [in a new window] [Download PPT slide]   Figure 21b.  Benign LFTP. (a, b) High-power (original magnification, x400) (a) and intermediate-power (original magnification, x200) (b) photomicrographs (hematoxylin-eosin [H-E] stain) demonstrate the bland, low-grade appearance of spindle-shaped tumor cells (a) that are arranged in a haphazard or so-called patternless pattern (b), the classic appearance of localized fibrous tumors. (c, d) High-power photomicrographs (original magnification, x400; H-E stain) of the same neoplasm demonstrate the variable cellularity characteristic of localized fibrous tumors. A hypercellular area (c) is composed of abundant spindle-shaped cells with a paucity of collagen fibers, whereas a hypocellular area (d) demonstrates abundant collagen (*) between tumor cells.

View larger version (186K): [in this window] [in a new window] [Download PPT slide]   Figure 21c.  Benign LFTP. (a, b) High-power (original magnification, x400) (a) and intermediate-power (original magnification, x200) (b) photomicrographs (hematoxylin-eosin [H-E] stain) demonstrate the bland, low-grade appearance of spindle-shaped tumor cells (a) that are arranged in a haphazard or so-called patternless pattern (b), the classic appearance of localized fibrous tumors. (c, d) High-power photomicrographs (original magnification, x400; H-E stain) of the same neoplasm demonstrate the variable cellularity characteristic of localized fibrous tumors. A hypercellular area (c) is composed of abundant spindle-shaped cells with a paucity of collagen fibers, whereas a hypocellular area (d) demonstrates abundant collagen (*) between tumor cells.

View larger version (183K): [in this window] [in a new window] [Download PPT slide]   Figure 21d.  Benign LFTP. (a, b) High-power (original magnification, x400) (a) and intermediate-power (original magnification, x200) (b) photomicrographs (hematoxylin-eosin [H-E] stain) demonstrate the bland, low-grade appearance of spindle-shaped tumor cells (a) that are arranged in a haphazard or so-called patternless pattern (b), the classic appearance of localized fibrous tumors. (c, d) High-power photomicrographs (original magnification, x400; H-E stain) of the same neoplasm demonstrate the variable cellularity characteristic of localized fibrous tumors. A hypercellular area (c) is composed of abundant spindle-shaped cells with a paucity of collagen fibers, whereas a hypocellular area (d) demonstrates abundant collagen (*) between tumor cells.

View larger version (179K): [in this window] [in a new window] [Download PPT slide]   Figure 22.  Benign LFTP. High-power photomicrograph (original magnification, x400; H-E stain) of a benign LFTP demonstrates the characteristic ropy collagen that occurs in the hypocellular areas of these lesions.

View larger version (181K): [in this window] [in a new window] [Download PPT slide]   Figure 23.  Benign LFTP. Low-power photomicrograph (original magnification, x100; H-E stain) demonstrates the second most commonly encountered histologic pattern (hemangiopericytoma-like) characterized by staghorn-like vessels.

View larger version (189K): [in this window] [in a new window] [Download PPT slide]   Figure 24.  Malignant LFTP. High-power photomicrograph (original magnification, x400; H-E stain) demonstrates five mitotic figures within this one high-power field. Note the nuclear pleomorphism that may also characterize malignant LFTP.

LFTP are reported to affect predominantly the middle and inferior hemithorax (11,45) (Figs 6–8, 12), and when in contiguity with the diaphragm, an LFTP may mimic diaphragmatic elevation (Fig 7). LFTP may exhibit slow growth over time (Fig 9) and may reach enormous sizes (46). Large lesions or those that arise from paramediastinal pleural surfaces may manifest with typical radiographic features of pulmonary or mediastinal masses, respectively (14,47). Pleural effusion is reported in 6%–17% of cases and may obscure a lesion in the inferior hemithorax (Fig 10) (11,18,21,48). To our knowledge, radiographic evidence of chest wall involvement by LFTP has been previously documented in only one case report (45).

Computed Tomography.— CT of small LFTP typically demonstrates homogeneous, well-defined, noninvasive, lobular, soft-tissue masses, which typically abut a pleural surface, may form obtuse angles against the adjacent pleura, or may be located within a fissure (Figs 9, 25) (11,26, 49). Large lesions are typically heterogeneous and may not exhibit CT features suggestive of focal pleural tumors (50). In fact, LFTP usually form acute angles against adjacent pleural surfaces (11,26,46,50) (Figs 9, 11–13, 16) (Table 2). Only 33% of the LFTP in our series exhibited at least one obtuse or right angle, and only 3% exhibited only obtuse angles (Figs 9, 25). Interestingly, the average sizes of the latter subsets of lesions (10.2 and 4.0 cm, respectively) were smaller than the average size of all the LFTP in the series. Dedrick and colleagues (26) stated that a smoothly tapering margin adjacent to the tumor (seen in five of their six cases) was a more characteristic finding that could help establish the pleural location of these tumors. However, this finding was demonstrated in only one-third of our cases (Fig 13). Dedrick and colleagues (26) also reported diaphragmatic crural thickening in one of their cases and a fissural location in another. Although fissural extension of the mass may be helpful in establishing lesion location, it is an uncommon finding (Fig 9). In addition, CT findings may not allow differentiation of a fissural LFTP from a peripheral lung lesion or exclusion of a tumor of abdominal origin when the inferior hemithorax is affected (49,51).

View larger version (130K): [in this window] [in a new window] [Download PPT slide]   Figure 25.  Benign LFTP in a 55-year-old man undergoing evaluation for HIV disease. Unenhanced chest CT scan (bone window) demonstrates a small well-defined mass of the left superior hemithorax that forms obtuse angles with the adjacent pleural surfaces.

View larger version (161K): [in this window] [in a new window] [Download PPT slide]   Figure 26a.  Malignant LFTP in an asymptomatic 37-year-old man. (a) PA chest radiograph demonstrates a lobular mass in the right cardiophrenic angle. Note poor visualization of the superolateral border of the lesion. (b) Unenhanced chest CT scan (mediastinal window) demonstrates a spherical heterogeneous right paracardiac mass that produces mass effect on the heart and perilesional atelectasis. Note the small ipsilateral right pleural effusion.

View larger version (127K): [in this window] [in a new window] [Download PPT slide]   Figure 26b.  Malignant LFTP in an asymptomatic 37-year-old man. (a) PA chest radiograph demonstrates a lobular mass in the right cardiophrenic angle. Note poor visualization of the superolateral border of the lesion. (b) Unenhanced chest CT scan (mediastinal window) demonstrates a spherical heterogeneous right paracardiac mass that produces mass effect on the heart and perilesional atelectasis. Note the small ipsilateral right pleural effusion.

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figure 27a.  Benign LFTP in a 27-year-old woman with chest pain. Contrast-enhanced chest CT scans (mediastinal window) demonstrate a heterogeneously enhancing mass of the left middle hemithorax that produces pressure erosion on an adjacent rib. The lesion forms obtuse and acute angles with the adjacent pleura and exhibits a smoothly tapering margin (b). Note enhancing serpiginous linear structures within the lesion (a), which likely represent vascular structures.

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 27b.  Benign LFTP in a 27-year-old woman with chest pain. Contrast-enhanced chest CT scans (mediastinal window) demonstrate a heterogeneously enhancing mass of the left middle hemithorax that produces pressure erosion on an adjacent rib. The lesion forms obtuse and acute angles with the adjacent pleura and exhibits a smoothly tapering margin (b). Note enhancing serpiginous linear structures within the lesion (a), which likely represent vascular structures.

The majority of the lesions in our series exhibited heterogeneous attenuation on CT scans before and after the administration of intravenous contrast material. Only benign LFTP exhibited homogeneous attenuation, which was more commonly seen on unenhanced scans (Fig 13). Homogeneity of attenuation may indirectly relate to size (as small lesions may exhibit necrosis less frequently) and was seen in lesions with average sizes of 8.1 cm on unenhanced CT scans and 4.6 cm on enhanced scans. In addition, hemorrhage, necrosis, or cystic change were absent in seven of eight lesions (88%) with homogeneous attenuation on unenhanced scans and in all eight LFTP with homogeneous attenuation on contrast-enhanced CT scans. Heterogeneous areas of low attenuation on unenhanced CT scans correlated with gross presence of necrosis, hemorrhage, or cystic change in 86% of benign LFTP.

Heterogeneous attenuation of LFTP after contrast material administration was typical (Figs 15–17) and correlated with gross descriptions of hemorrhage, necrosis, or cystic change in 22 of 40 (55%) cases of benign LFTP with intrinsic areas of low attenuation (Figs 16, 17). Little has been written about the CT appearance of malignant LFTP. They are described as indistinguishable from benign lesions: large masses of heterogeneous attenuation and patchy enhancement (52). Although there was no difference in lesion size when the benign and malignant LFTP in our series were compared, low-attenuation areas were seen in all malignant LFTP whether the scans were obtained before or after the administration of intravenous contrast material and correlated with gross descriptions of hemorrhage, necrosis, or cystic change in 60% of unenhanced (Figs 12, 26) and 54% of enhanced CT studies (Fig 28).

View larger version (133K): [in this window] [in a new window] [Download PPT slide]   Figure 28a.  Malignant LFTP in an asymptomatic HIV-positive 28-year-old woman. (a) Contrast-enhanced chest CT scan (mediastinal window) demonstrates an irregular soft-tissue mass in the left middle hemithorax that exhibits heterogeneous enhancement and internal geographic areas of low attenuation. (b) Photograph of the resected specimen demonstrates a centrally necrotic mass. Note that complete excision of the LFTP required a pneumonectomy.

View larger version (155K): [in this window] [in a new window] [Download PPT slide]   Figure 28b.  Malignant LFTP in an asymptomatic HIV-positive 28-year-old woman. (a) Contrast-enhanced chest CT scan (mediastinal window) demonstrates an irregular soft-tissue mass in the left middle hemithorax that exhibits heterogeneous enhancement and internal geographic areas of low attenuation. (b) Photograph of the resected specimen demonstrates a centrally necrotic mass. Note that complete excision of the LFTP required a pneumonectomy.

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 29a.  Benign LFTP in a 64-year-old woman who presented with confusion and hypoglycemia. (a) Sagittal T1-weighted MR image demonstrates a large soft-tissue mass of heterogeneous intermediate signal intensity in the right hemithorax that produces mass effect on the hemidiaphragm. Note flow void foci consistent with tumor vessels. (b) Sagittal T2-weighted MR image at the same level demonstrates an overall heterogeneous increase in signal intensity in the lesion with multiple hyperintense areas.

View larger version (145K): [in this window] [in a new window] [Download PPT slide]   Figure 29b.  Benign LFTP in a 64-year-old woman who presented with confusion and hypoglycemia. (a) Sagittal T1-weighted MR image demonstrates a large soft-tissue mass of heterogeneous intermediate signal intensity in the right hemithorax that produces mass effect on the hemidiaphragm. Note flow void foci consistent with tumor vessels. (b) Sagittal T2-weighted MR image at the same level demonstrates an overall heterogeneous increase in signal intensity in the lesion with multiple hyperintense areas.

Ultrasonography.— US is helpful in the evaluation of large masses in the inferior hemithorax through visualization of the diaphragm and establishment of their intrathoracic location, particularly those lesions located in the inferior hemithorax (4,26) (Fig 17b).

Patient Management
Diagnosis.— The diagnosis of LFTP may not be suggested prospectively after imaging affected patients. This is not surprising given the fact that classically described radiographic features (incomplete visualization of the lesion borders, fissural location) and cross-sectional imaging features (obtuse angles, mobility, pedicle visualization) of focal pleural masses are usually not present in these cases. The diagnosis of LFTP is typically made after surgical excision of the mass. Confident preoperative diagnosis can be made with large-bore cutting needle biopsies, and because the needle can usually be introduced into the mass while avoiding aerated lung, the risk of pneumothorax is minimal (56). Although fine-needle aspiration may yield characteristic and diagnostic morphologic features, cutting needle biopsy is probably preferable because of wider tissue sampling (10,56).

Treatment.— The therapy for patients with LFTP is complete surgical excision. Aggressive surgery is recommended given the possibility of recurrent disease (57). Vascular adhesions to adjacent tissues may result in massive intraoperative hemorrhage, which is adequately handled with good exposure, prompt removal of the mass, and meticulous hemostasis (58). Cardillo and colleagues (6) described 55 patients with LFTP who underwent resection via video-assisted thoracoscopic surgery (VATS) and thoracotomy with no operative deaths. Although VATS may be adequate for the resection of small tumors, large tumors usually require a thoracotomy (39). In many cases, resection of the lesion with its pedicle and a small patch of adjacent lung may be sufficient (4). In some cases, complete excision may require lung resection (segmentectomy, lobectomy, bilobectomy, pneumonectomy), partial pleurectomy, or en bloc chest wall resection (Fig 28b) (4,6,7,12). Long-term imaging follow-up is recommended in all cases to exclude tumor recurrence or metastatic disease. Recurrent disease typically affects the ipsilateral pleura and may also affect the lung. Repeat resection of recurrent lesions is recommended (4,49). Adjuvant therapy is probably not helpful because of the low cellular content and low mitotic rates characteristic of LFTP (27,59).

Prognosis.— The prognosis for patients with LFTP is generally favorable. The majority of lesions behave in a benign fashion (88%), but approximately 12% of patients die of extensive intrathoracic tumor growth or an unresectable recurrence (3). Although tumor size does not directly correlate with prognosis, pedunculated noninvasive tumors are less likely to recur when complete excision of all neoplastic tissue is accomplished. In fact, complete excision is the best prognostic indicator (3,7,8,21,25,60). Malignant lesions can be successfully resected particularly if they are pedunculated (49,60). Recurrent tumors may exhibit malignant histologic features and a more aggressive biologic and clinical behavior despite prior resection of histologically benign lesions (14). Malignant tumors may metastasize, and local recurrences are more common in cases of malignant lesions than in benign lesions (22).

	Conclusions

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Materials and Methods Results Discussion Conclusions References

 
Localized fibrous tumors are rare primary pleural neoplasms that may grow to large sizes and typically affect symptomatic men and women over the age of 40 years. Small LFTP may be discovered incidentally on chest radiographs of asymptomatic individuals. Although small lesions may exhibit the characteristic imaging features of pleural masses, classic findings of focal pleural disease, such as the "incomplete border" sign, obtuse or right angles against the adjacent pleura, fissural location, or mobility within the pleural space, are usually absent. The majority of LFTP occupy the inferior hemithorax, and those that abut the ipsilateral hemidiaphragm may mimic diaphragmatic elevation or eventration. The diagnosis should be considered in symptomatic adults who present with solitary, large, lobular, heterogeneous intrathoracic masses in the absence of local invasion, lymphadenopathy, or metastatic disease. Small LFTP without gross necrosis, hemorrhage, or cystic change may exhibit homogeneous attenuation on unenhanced and less frequently on contrast-enhanced chest CT scans. However, the majority of LFTP exhibit heterogeneous attenuation on CT scans, characterized as intralesional geographic, focal or linear areas of low attenuation that often correlate with hemorrhage, necrosis, or cystic changes. Calcification may occur in one-fourth of cases. Atelectasis of the adjacent lung and mass effect on the mediastinum are common associated findings. MR imaging typically demonstrates intrathoracic lobular masses of heterogeneous signal intensity with both T1- and T2-weighted sequences. Internal low-signal-intensity septa on T2-weighted images are common. Studies that allow direct visualization of the diaphragm such as MR imaging and US are useful in establishing the intrathoracic location of large lesions occupying the inferior hemithorax. Although there are no imaging features that definitively distinguish benign from malignant subtypes of LFTP, heterogeneity on cross-sectional images, mass effect, and pleural effusion may be slightly more common in malignant lesions.

	Acknowledgments

 
The authors wish to acknowledge the immense assistance of Linda C. Wilkins, BS, who constructed the database used to collect and analyze the data for the manuscript. We also acknowledge the input and contribution of Philip A. Templeton, MD, during the early planning stages of the project. Finally, we thank the countless residents who throughout the years have participated in the Radiologic Pathology Courses of the Department of Radiologic Pathology at the Armed Forces Institute of Pathology in Washington, DC. Their case contributions enriched the content of the Institute’s archives and enhanced our understanding of radiologic-pathologic correlation of thoracic diseases.

	Footnotes

 
Abbreviations: AFIP = Armed Forces Institute of Pathology, H-E = hematoxylin-eosin, LFTP = localized fibrous tumors of the pleura, PA = posteroanterior

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 Air Force, Navy, Army, or Defense.

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