Solitary fibrous tumors (SFTs) are well-circumscribed spindle-cell mesenchymal neoplasms with hemangiopericytoma-like pattern with characteristic branching vessels (“staghorn vessels”) and other histologic patterns. Also known as localized fibrous tumors, SFTs are the most common benign pleural tumor. Most SFTs are attached to the visceral pleura, but they may be attached to the parietal pleura or may be intrapulmonary. Typically, SFTs are 5 to 10 cm in greatest dimension and may be found incidentally. Large benign SFTs may compress adjacent lung and other structures, but despite the sometimes distressing clinical presentation, do not invade these adjacent structures and are cured by resection. On the other hand, large size can be associated with malignancy, and careful sampling is recommended (see Chapter 15, Part 6). SFTs are occasionally multiple, which is why some investigators prefer calling them localized fibrous tumors. On cut section they typically have a fibrous appearance and consistency, usually off-white, firm, and often whorled. Hypoglycemia occasionally is seen with some patients.