Subcutaneous solitary fibrous tumor

We describe a unique case of subcutaneous solitary fibrous tumor (SFT) in a 56-year-old female patient. The patient had been aware of a painless soft mass in her back for ten years. The lesion was surgically excised. Histological examination revealed that the well-defined mass was composed of a proliferation of spindle-shaped fibroblastic cells and polygonal cells embedded in a fibrous matrix corresponding to the so-called "patternless pattern". A prominent pericytomatous pattern (hemangiopericytoma-like structures), focal myxoid changes, and thick hyalinized collagen fibers were also observed. Immunohistochemical stainings for CD34 and bcl-2 were positive in the tumor cells. These features are compatible with SFT. We suggest that SFT should be included in the differential diagnosis of subcutaneous spindle cell tumors.