Solitary fibrous tumor of soft tissue: a case report and immunohistochemical study.

A case of solitary fibrous tumor (SFT) arising in the soft tissue of the left inguinal region is reported. A 57-year-old Japanese woman presented with a nonadherent, well-defined, oval mass that was 2 x 3 cm in diameter and located in the inguinal soft tissue. Microscopic evaluation showed proliferation of spindle-shaped, fibroblast-like cells by the coexistence of hypo- and hypercellular areas with mast cell infiltration separated by hemangiopericytoma-like blood vessels. Immunohistochemistry revealed strong expression of CD34 and CD99 in the fibroblast-like cells, supporting the diagnosis of SFT. Although the patient was free of symptoms such as hypoglycemia, immunoreactive insulin-like growth factor (IGF)-II was localized in the socalled Golgi area of the spindle-shaped cells. In conclusion, immunoreactive IGF-II was detected in SFT that was not associated with hypoglycemia.