IS case 458: Solitary fibrous tumor
Imaging Sciences URMC 2010
Publication Date: 2010-08-30
Solitary fibrous tumor of the pleura, also called pleural fibroma or benign fibrous mesothelioma, originates from the submesothelial connective tissue of the pleura. The etiology is unknown and is not associated with smoking or asbestos exposure and is not to be confused with mesothelioma, which arises from the mesothelium. Approximately half of patients have symptoms at presentation, usually due to the local compressive effect. Paraneoplastic syndromes are not uncommon, with hypertrophic osteoarthropathy occurring in up to 30% of patients, more common in larger tumors. Doege-Potter syndrome is seen in approximately 5% of patients, which is characterized by hypoglycemia of unknown origin. Classification criteria are dependent on the tumor being benign versus malignant and broad-based versus pedicle attachment to the pleura. Malignant broad based tumors have the highest rate of reoccurrence (approximately 63%), with benign pedical attached tumors having the lowest rate of reoccurrence. Approximately 80-85% are benign, while 15-20% are malignant and have a poor prognosis. Unfortunately, malignant and benign tumors are indistinguishable with imaging.
Characteristic radiographic findings include a peripheral, lobulated, sharply-marginated mass with the longitudinal axis paralleling the chest wall. The incomplete border sign and obtuse margins of the tumor with the chest wall, are helpful to localize the mass outside the lung parenchyma, when present. Depending on location, a pleural fibroma may mimic a mediastinal mass or an elevated diaphragm. A characteristic imaging feature, when present, is changing location of a large pedunculated lesion with changes in patient position. Pleural effusions are present in greater than 20% of cases.
On CT, the tumor displaces surrounding structures rather than invading. Calcification can be seen in approximately 5% of benign lesions, and up to 20% of malignant lesions. Pleural fibromas enhance with contrast, often greater than or equal to muscle. Heterogeneous enhancement can be seen with larger tumors, correlating with myxoid degeneration or necrosis in malignant tumors. On MRI, low T1W and T2W signal is characteristic, which correlates to extensive fibrous elements; however, patchy high T2W signal can be seen with myxoid cystic regions or necrosis.
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