Palisading subcutaneous fibrous histiocytoma.

A case of palisading subcutaneous fibrous histiocytoma, a very rare variant of fibrous histiocytoma (dermatofibroma), arising in the wrist of a 41-year-old man is presented. An unencapsulated subcutaneous tumor measuring 0.8 x 0.8 x 0.7 cm was histologically characterized by predominant nuclear palisading and a peripheral area with a pattern quite characteristic of conventional fibrous histiocytoma. Immunohistochemically, the tumor cells were strongly positive for vimentin, alpha-smooth muscle, and muscle actin, but negative for S-100 protein, indicating a fibroblastic or myofibroblastic nature. The patient has been well without recurrence for 6 years and 8 months after the excision. This neoplasm should be differentiated from benign and malignant skin or soft tissue tumors with a palisading pattern. Pathologists and clinicians should know of the existence of this type of fibrous histiocytoma and should avoid overdiagnosis and overtreatment.