Leiomyosarcoma and Pleomorphic Dermal Sarcoma: Guidelines for Diagnosis and Treatment.

There are 3 types of leiomyosarcoma of the skin: dermal, subcutaneous, and metastatic cutaneous. Dermal leiomyosarcoma arises from smooth muscle fibers in arrector pili muscles, genital dartos muscles, and the nipple-areola complex. It is an intermediate-grade tumor associated with a tendency for local recurrence (24%) and low metastatic potential (4%). Subcutaneous leiomyosarcoma originates from smooth muscle in blood vessel walls and has higher rates of local recurrence (37%) and metastasis (43%). Plemorphic dermal sarcoma typically affects elderly patients and arises in sun-exposed areas (e.g., the scalp). Its histologic and immunohistochemical characteristics are similar to those of atypical fibroxanthoma, but it is more aggressive (metastasis rate of 10-20%). Histologically, it can be distinguished from atypical fibroxanthoma by the observation of subcutaneous tissue invasion, perineural invasion, and foci of necrosis.