Solid Pleural Lesions

Transcription

1 Residents Section Pattern of the Month Hussein-Jelen et al. Solid Pleural Lesions Residents Section Pattern of the Month Residents inradiology Tamara Hussein-Jelen 1,2 lexander. ankier 1 Ronald L. Eisenberg 1 Hussein-Jelen T, ankier, Eisenberg RL Keywords: pleural effusion, pleural lesions, pleural space DOI: /JR Received July 25, 2011; accepted after revision ugust 19, Department of Radiology, eth Israel Deaconess Medical Center, Harvard Medical School, 330 rookline ve, oston, M ddress correspondence to R. L. Eisenberg (rleisenb@bidmc.harvard.edu). 2 Present address: Institut für Diagnostiche und Interventionelle Radiologie, Klinikum Klagenfurt am Wörthersee, Klagenfurt, ustria. WE This is a Web exclusive article. JR 2012; 198:W512 W X/12/1986 W512 merican Roentgen Ray Society Solid Pleural Lesions T he pleural space is the cavity between the lungs and chest wall. It consists of a serous membrane, which folds back onto itself to form a two-layered structure. The inner visceral cover the lungs, blood vessels, bronchi, and nerves. The outer parietal pleura are attached to the chest wall. The pleural cavity normally contains up to 5 ml of pleural fluid. When assessing pleural lesions, one should consider morphologic criteria: whether the abnormality is solitary or multiple, unilateral or bilateral, calcified or noncalcified. The most common solid pleural lesions (Table 1) include benign, malignant, and borderline processes. The most common solid pleural lesion-mass is pleural thickening, which can be localized or diffuse, unilateral or bilateral, and calcified or noncalcified. mong pleural neoplasms, malignant tumors (particularly metastases) are more common than benign tumors. to the pleura develop from hematogenous spread of cancer cells through the bloodstream, lymphangitic spread, or direct contact by malignant neoplasms in the lung. Malignant lesions are accompanied by pleural effusion, which is often bloody. pleural tap with removal of a small amount of fluid for histologic analysis can provide accurate diagnostic information, and drainage of large amounts of pleural fluid offers symptomatic relief (Table 2). Pleural effusion is probably the most common and clinically important secondary finding caused by pleural lesions. They may be unilateral or bilateral depending on the underlying cause. Histologically, pleural effusion can represent either exudate or transudate. Transudative effusions, often caused by chronic heart failure, uremia, or hypoalbuminemia due to an imbalance of hydrostatic and oncotic forces, are characterized by their low protein content and specific gravity. In contrast, exudates are frequently caused by infection, infarction, or malignancy and have high levels of protein and lactate dehydrogenase and elevated specific gravity. Chest radiography does not permit the differentiation between exudate and transudate. Even when using attenuation measurements, the ability of CT to make this distinction is limited. Consequently, pleural tapping is often re- TLE 1: Most Common Causes of Solid Pleural Lesions quired to establish a final diagnosis. Transthoracic ultrasound may be of value in determining the appropriate site of needle insertion. Pleural enign lesions thickening Pleural Thickening enign pleural thickening is defined as a continuous process more then 5 cm wide, 8 cm in craniocaudal extent, and 3 mm thick, all of which are best measured on CT. The costal and paravertebral regions are most commonly involved; the mediastinal pleura are rarely affected. Hypertrophy of extrapleural fat due to a chronic pleural disease can produce an appearance simulating pleural thickening. enign pleural thickening is the second most common pleural abnormality (after pleural pical pleural cap Diffuse pleural fibrosis Lipoma Splenosis orderline lesions Fibrous tumor of the pleura Malignant lesions Mesothelioma skin tumor W512 JR:198, June 2012

2 Solid Pleural Lesions effusion). Often asymptomatic, it can cause dyspnea because of restrictive lung function changes. Whether pleural thickening is associated with pleural effusion depends on the underlying disease. pical Pleural Cap Thickening of the apical pleural cap is a harmless sign of normal aging that may be due either to intrapulmonary and pleural fibrosis pulling down extrapleural fat or to chronic ischemia. Other causes include a hematoma resulting from aortic rupture or another fluid collection due to infection or tumor (Fig. 1). n apical pleural cap appears radiographically as sharply marginated pleural thickening that may have a smooth or undulating border. It most commonly occurs on the right, but may be bilateral. pical pleural thickening that is more than 2 cm larger than the contralateral side is suspicious for a malignant Pancoast tumor (Fig. 2). TLE 2: Pattern of Pleural Diseases Unilateral Calcified Solitary Fibrous tumor of the pleura after therapy Multiple after therapy Noncalcified Solitary Fibrous tumor of the pleura Lipoma Mesothelioma skin tumor Diffuse Pleural Fibrosis Multiple Diffuse pleural fibrosis can be caused by asbestosis, pulmonary fibrosis, empyema, hemo- Splenosis (left side) thorax, thoracic irradiation, previous surgery, trauma, tuberculous pleurisy, and drugs. The diffuse form is often associated with volume loss, calcifications (Figs. 3 and 4), and an accumulation of extrapleural fat. ilateral Calcified Chest radiographs show diffuse pleural thickening, along with other pathologic findings depending on the underlying disease. after therapy For example, pleural thickening combined Noncalcified with upper lobe fibrosis and calcifications suggests tuberculosis. When paired with rib fractures and prior hemothorax, trauma is likely the underlying cause, whereas a combination of pleural thickening with rib de- struction raises the possibility of aggressive fibromatosis. complicating round atelectasis (Figs. 5 and 6) can enclose and bind the lung, causing dyspnea due to restrictive lung function that may be so severe as to require surgical therapy (such as decortication). On contrast-enhanced CT, enhancement of thickened pleura may be seen in aggressive fibromatosis, whereas it is much less common in other forms of pleural thickening. In asbestosrelated disease, pleural thickening has a relatively symmetric distribution, often with pleural effusion. hallmark of this condition is calcification of the parietal pleura. Lipoma enign lipoma is the most common tumor of the pleura. It is usually asymptomatic and often an incidental finding on chest radiography or CT. Radiographically, a lipoma has a sharply defined margin in profile but appears unsharp on en face views. On CT, a benign lipoma is a homogeneous oval or lenticular lesion with pathognomonic fat density and no contrast enhancement (Fig. 7). The presence of a contrast-enhancing component within a fatty mass is suspicious for liposarcoma and should be systematically ruled out by MRI or biopsy. JR:198, June 2012 W513

3 Hussein-Jelen et al. Fig. 1 Pancoast tumor. Increased opacification in right apex (arrows). lthough this appearance may simulate benign apical pleural thickening, marked asymmetry and irregularity of right apical mass should suggest diagnosis of bronchogenic carcinoma. Fig. 2 Pancoast tumor. and, Radiograph () shows subtle area of increased opacification in left apical region, and coronal CT image () clearly shows irregular malignant lesion invading chest wall and mediastinum. Splenosis Pleural splenosis results from the posttraumatic autotransplantation of splenic tissue on the left parietal or visceral pleura (or even on the pericardium) after rupture of the spleen and diaphragm. This condition can be asymptomatic and an incidental finding or produce chest pain. If the diagnosis of splenosis is made, the patient must be informed that thoracic trauma could result in severe bleeding. Chest radiography and CT show splenosis as multiple soft-tissue lesions of different sizes. Uncomplicated cases are not associated with pleural effusion. On CT, the lesions in splenosis show contrast enhancement that is identical to that of the spleen. However, the imaging modality of choice is scintigraphy because the lesions of splenosis accumulate 99m Tc heat-damaged tagged erythrocytes. SPECT or SPECT-CT may be helpful for anatomic correlation. Fibrous Tumor of the Pleura Fibrous tumor of the pleura is a pedunculated mesenchymal lesion with variable microscopic appearance and unpredictable biologic behavior. lthough most of these tumors are benign, they are malignant in 20% of cases. Fibrous tumor should be included in the differential diagnosis of any unilateral pleural lesion that shows gradual but slow growth over many years. Fibrous tumor of the pleura usually arises between ages 45 and 60 years. lthough about 25% of patients are asymptomatic, most suffer from such symptoms as dyspnea, chest pain, W514 JR:198, June 2012

4 Solid Pleural Lesions Fig. 3 Pleural plaques. and, xial CT images show noncalcified () and partly calcified () pleural plaques (arrows). Fig. 4 Completely calcified pleural plaques. and, xial CT images show focal () and widespread () lesions (arrows). Fig. 5 Round atelectasis. xial CT image shows small area of involvement in right lower lobe (arrows). and cough. classic but rare condition associated with benign fibrous tumor of the pleura is hypoglycemia and hypertrophic osteoarthropathy (Pierre-Marie-amberger syndrome). fter resection, 15% of fibrous tumors of the pleura recur. Therefore, imaging follow-up is suggested, although it is not clear for how long this is necessary, On chest radiographs, a fibrous tumor of the pleura appears as a solitary, peripheral, mobile, sharply defined, and homogeneous nodule or mass, often larger than 7 cm in diameter (Fig. 8). Malignant forms can show calcification and effusion, but this is seen in only 20% of cases. On CT, a large fibrous tumor of the pleura may contain areas of necrosis, hemorrhage, and cystic change and almost always shows contrast enhancement. On MRI, fibrous tumors of the pleura are hypointense on both T1- and T2-weighted images because they contain large amounts of collagen. High signal intensity on T2-weighted images reflects necrosis, cystic degeneration, or inhomogeneous distribution of vascular structures. The tumor shows intense heterogeneous enhancement after IV injection of gadolinium (Fig. 9). JR:198, June 2012 W515

5 Hussein-Jelen et al. Fig. 6 Round atelectasis. and, Coronal CT images show large area of involvement in right lower lung (arrows). Fig. 7 Pleural lipoma. xial CT image with mediastinal windows shows smoothly marginated mass with fat attenuation in apex of right lung. Fig. 8 enign localized fibrous tumor of pleura. Radiograph shows huge homogeneous soft-tissue mass (arrows) arising from mediastinal pleura and projecting in right hemithorax. The pleura are a common site of metastases, especially from primary adenocarcinomas. bout 40% are caused by bronchogenic carcinoma, 20% by breast carcinoma, 10% by lymphoma, and 10% by tumors of unknown origin. lthough pleural metastases may be asymptomatic in 20% of patients, they generally cause dyspnea, chest pain, and weight loss. Pleural metastases are the second most common cause of pleural effusion in adults (the first is left heart failure). Other important causes include right heart failure and pulmonary hypertension. Chest radiography and CT show pleural metastases as diffuse or focal pleural thickening (Figs ). This may be nodular thickening, a discrete mass, or circumferential pleural thickening with infiltration into adjacent tissues. PET/CT can distinguish benign from malignant pleural thickening and effusion by showing high 18 F-FDG-uptake in the latter. Mesothelioma Mesothelioma is a rare malignant tumor of the pleura that is related to asbestos exposure and has a poor prognosis, with an average survival time of 12 months. The latency time from asbestos exposure is around 30 to 45 years, so that the tumor usually occurs in men between 50 and 70 years old. The risk of developing a mesothelioma increases when there is a high length-to-width ratio of the asbestos fiber (i.e., longer and thinner fibers). lthough all forms W516 JR:198, June 2012

6 Solid Pleural Lesions Fig. 9 Large fibrous tumor of pleura. xial CT image shows inhomogeneous matrix of tumor (solid arrows) as well as scattered calcifications (white open arrow) and thickened blood vessels (black open arrow). Fig. 10 Small fibrous pleural tumor. and, xial soft-tissue CT image () and coronal image with lung windows () show absence of chest wall invasion and slightly inhomogeneous texture of tumor (arrow). Fig. 11 Pleural metastases (bronchogenic carcinoma). Radiograph shows diffuse pleural thickening along upper left chest wall (arrows). Elevation of left hemidiaphragm reflects involvement of phrenic nerve and postobstructive atelectasis secondary to left perihilar lesion. Fig. 12 Pleural metastases (breast carcinoma). xial CT image shows diffuse pleural thickening with nodular components (white arrows) accompanied by pleural effusion. Note multiple low-attenuation metastases in liver (black arrows). JR:198, June 2012 W517

7 Hussein-Jelen et al. Fig. 14 Pleural and extrapleural metastases (lung carcinoma). xial CT image shows massive chest wall destruction (arrows), accompanied by small pleural effusion and diffuse metastatic pleural disease in right paracardiac region. Fig. 13 Pleural metastases (breast carcinoma). xial CT image shows plastic reconstruction of right breast after mastectomy, with contralateral pleural metastases involving left major fissure (arrows). Fig. 15 Pleural metastases (lung carcinoma). xial CT image after contrast administration shows hypervascularized pleural metastases with surrounding pleural effusion (arrows). On unenhanced images, these lesions would be substantially more difficult to visualize. of asbestos are carcinogenic, the brittle and needle-shaped amphiboles are considered to be the most dangerous because they break apart easily and become tiny airborne particles that can be easily inhaled and then migrate through the airways to deposit in the pleura. The initial symptoms of mesothelioma may be chest pain, dyspnea, fever, and weight loss, although some cases are detected in asymptomatic individuals. On chest radiographs, about 95% of patients with mesothelioma have a pleural effusion as the only finding (Fig. 16). generally is lobulated, and coexisting calcified pleural plaques may suggest previous asbestos exposure. n important distinction from metastases is that mesotheliomas are always unilateral (Fig. 17), and there generally is volume loss of the affected hemithorax CT can precisely show tumor infiltration of other structures, such as the thoracic wall, mediastinum, and diaphragm, which is an important factor in planning surgical therapy. Curiously, mesotheliomas tend to spread along tracts produced by chest tubes and thoracoscopy trocars or punctures. Lower chest CT sections may show diffuse calcifications within metastases to the liver. On MRI, mesotheliomas are relatively isointense or slightly hyperintense to muscle on T1-weighted images and moderately hyperintense on T2-weighted sequences. They enhance strongly after IV injection of gadolinium. W518 JR:198, June 2012

8 Solid Pleural Lesions Fig. 16 Diffuse pleural mesothelioma. Chest radiograph obtained after thoracentesis shows top of large lobulated mass (arrow). (Reprinted with permission from Ellis K, Wolff M. Mesotheliomas and secondary tumors of pleura. Semin Roentgenol 1977; 12: ) Fig. 17 Mesothelioma. xial CT image shows extensive nodular pleural thickening with strictly unilateral distribution (arrows). Fig. 18. xial CT image shows multiple bilateral foci of pleural thickening with accompanying right hilar adenopathy but no pleural effusion (arrows). Pleural lymphoma usually is a secondary manifestation of previously diagnosed disease. Clinical symptoms include chest pain, fever, and chest wall swelling. Chest radiographs show pleural effusion and focal or diffuse pleural thickening. ssociated mediastinal lymphadenopathy is well seen on CT (Fig. 18). This modality also may show a flat broad-based lymphomatous plaque, which may invade the chest wall without rib involvement. Unlike other malignant tumors, lymphoma often shows homogeneous contrast enhancement, usually without signs of necrosis. fter chemotherapy, cystic changes and calcifications may develop. n important distinction from other malignant pleural tumors is that lymphoma of the pleura is usually merely one part of a systemic process, with PET/CT showing increased uptake of radioactive FDG in all affected lymph nodes. skin Tumor skin tumor is a malignant tumor that belongs to the group of primitive neuroectodermal tumors and has a poor prognosis, with an average survival time of 8 months. skin tumor may develop on a genetic basis, associated with a translocation of chromosome 22, or it may occur after radiation therapy for Hodgkin lymphoma. The lesion most commonly occurs in young women, shows very rapid growth, and may cause chest pain. Chest radiography generally shows a large unilateral pleural mass with pleural effusion. In most cases, skeletal metastases are already evident at the time of diagnosis. CT more precisely shows infiltration of the thoracic wall, mediastinum, and lung as well as skeletal and pulmonary metastases and spread to mediastinal lymph nodes. unique feature of skin tumor is metastasis to the sympathetic chain. JR:198, June 2012 W519

9 Hussein-Jelen et al. Suggested Reading 1. onomo L, Feragalli, Sacco R, Merlino, Storto ML. Malignant pleural disease. Eur J Radiol 2000; 34: Hansell DM, ankier, MacMahon H, McLoud TC, Müller NL, Remy J. Fleischner Society: glossary of terms from thoracic imaging. Radiology 2008; 246: Huggins JT, Sahn S. Causes and management of pleural fibrosis. Respirology 2004; 9: Pistolesi M, Rusthoven J. Malignant pleural mesothelioma: update, current management, and newer therapeutic strategies. Chest 2004; 126: pleural space 5. Qureshi NR, Gleeson FV. Imaging of pleural disease. Clin Chest Med 2006; 27: Rosado-de-Christenson ML, bbott GF, Mcdams HP, Franks TJ, Galvin JR. From the archives of the FIP: localized fibrous tumors of the pleura. RadioGraphics 2003; 23: Safret, Oderbolz S, Looser P, Moll C. Der besondere Fall: Thorakale Splenose. Forum Med Suisse 2001; 12: W520 JR:198, June 2012