Solitary fibrous tumor of the skin.

Solitary fibrous tumor (SFT) is an uncommon tumor initially reported in the pleura but recently described in other sites of the body. We report a SFT of the skin that presented as painless nodule located in the right cheek in a 56-year-old woman. Histologically, the tumor was composed of spindle-shaped cells arranged in a patternless pattern of short and narrow fascicles with interspersed bundles of thick collagen, and numerous blood vessels with a focally hemangiopericytoma-like appearance. Immunohistochemically, the tumor cells strongly expressed vimentin, CD34 and bcl-2. The lesion was excised and the patient remains well at 16-month follow-up. This case presented some diagnostic difficulty because of its unusual location, and had to be distinguished from other superficial soft tissue tumors. Recognition of SFT in the skin is important to avoid possible confusion with a variety of spindle cell neoplasms with different biologic potential.