[Solitary fibrous tumor: a clinico-morphological and immunohistochemical study].

Solitary fibrous tumor is a rare neoplasm which may occur at any site although it is more frequent in the pleura, mediastinum and lung. The study used 4 cases of tumor localization in the pleura and orbit. Three cases presented as a "hemangiopericytic" variety of spindle cells; there were numerous giant cells in orbit tumor. Solitary fibrous tumor revealed enhanced expression of vimentin, CD34, bel-2 and CD99. Expression of S-100, desmine and non-striated muscle actin was found in few cells in some cases. Such features as large size (over 10 cm), necrosis, high cellularity, nuclear polymorphism and high mitotic index (more than 4 mitoses within 4 visual fields, at high magnification) were used as malignancy criteria:. Tumor histological pattern of "hemangiopericytic" variety could be reliably identified thanks to immunohistochemical procedure.