SOLITARY FIBROUS TUMORS - A SERIES OF LESIONS, SOME IN UNUSUAL SITES

Solitary fibrous tumor (SFT) is a rare neoplasm that, in addition to i ts classic presentation as a pleural-based mass, can also be encounter ed in unusual sites. The main difficulty in making the diagnosis of SF Ts results from the unfamiliarity with its diverse clinical and pathol ogic features, This series of SFTs, some with unusual clinicopathologi c presentation, included nine women and two men, ranging in age from 2 8 years to 74 years (five in pleura, one in lung parenchyma, one in br east, and four in mediastinum). The tumors were locally excised in eig ht cases and were resected along with portions of lung parenchyma in t hree. A panel of immunohistochemical stains was used to characterize t hese tumors. They were all vimentin-positive and, with the exception o f one case, CD34-positive, Tumors were negative with antibodies direct ed against cytokeratin, factor VIII-related antigen, S-100 protein, mu scle-specific actin, and smooth-muscle actin. Various diagnoses were i nitially rendered for these clinically and pathologically diverse lesi ons by the examining pathologists. Awareness of the various gross and microscopic patterns of these tumors, the possibility of occurring in unusual sites, and the use of immunohistochemical stains, particularly CD34, should eliminate most of the difficulties in arriving at a corr ect diagnosis. One patient died of metastatic breast cancer; all other patients were alive and well with a median follow-up of 17 months.