Leiomyosarcoma of the skin and subcutaneous tissue.

In a study of 65 primary cutaneous leiomyosarcomas and 15 primary superficial subcutaneous leiomyosarcomas, tumors occurred at any age but were more common in middle age and most common on the extremities. They developed as solitary painful or tender intracutaneous or subcutaneous nodules. Microscopically, the cutaneous leiomyosarcomas consist of a poorly delineated proliferation of spindle-shaped atypical myomatous cells arranged in interlacing fascicles which merge into collagenous stroma. Subcutaneous leiomyosarcomas are more sharply circumscribed and typically include a vascular pattern. About 40% of the cutaneous leiomyosarcomas recurred, but none metastasized despite a high mitotic frequency and marked cytologic atypia. Among the 12 patients with subcutaneous leiomyosarcomas, one-half of the tumors recurred and one-third eventuated in metastasis or tumor-related death. Cutaneous leiomyosarcomas have a relatively benign biologic course and may be excised conservatively, but are less likely to recur if the local excision is wide enough to require a skin graft for closure of the surgical defect. For primary subcutaneous leiomyosarcoma, early wide local excision with adequate clear histologic borders constitutes rational treatment.