A thoracic mass discovered at abdominal imaging

Solitary fibrous tumor of the pleura (SFTP) is a rare primary pleural neoplasm arising from the submesothelial mesenchymal cell layer just beneath the mesothelial lining of the pleura. SFTPs consist of spindle cells embedded within variable amounts of connective tissue, typically staining positive for vimentin and antibodies to CD34. SFTPs are often attached to pleural surfaces through a pedicle. Histopathologic criteria for malignancy include high mitotic counts (>4 mitoses per 10 high-power fields), pleomorphism, hypercellularity, tumor giant cells, necrosis, and hemorrhage. Chest radiography in patients with SFTP shows a peripheral mass displaying characteristics suggesting an extraparenchymal location: obtuse angles with the chest wall associated with a circumscribed border on one side of the lesion with an indistinct, "fading" margin on the opposite side of the lesion. Cross-sectional imaging findings of SFTP include a variably sized mass contacting the chest wall or the diaphragm, showing enhancement after intravenous contrast administration. Calcification and effusion are uncommon. Magnetic resonance imaging may show decreased T1 and T2 signal, suggesting the fibrous nature of SFTPs, and also typically shows intense, heterogeneous, intravenous contrast enhancement. The treatment of choice for SFTP is wide surgical resection.