Myofibrosarcoma treated with Mohs micrographic surgery

Myofibrosarcoma is a rare malignant mesenchymal tumor composed predominantly of differentiated myofibroblasts. These tumors occur in both children and adults alike and are most commonly located on the head and neck. Recurrences rates range from 44% to 75%, and metastatic disease has been reported in up to 44% of cases.

The objective was to present a case of a myofibrosarcoma treated with Mohs micrographic surgery and discuss the use of ultrastructural evaluation in the diagnosis of this rare tumor.

A 31-year-old African American woman who presented to the Emory University Dermatologic Surgery Clinic with a 4-month history of a 2.5 x 2.5-cm indurated firm painful right upper lateral thigh nodule. A prior biopsy revealed a proliferation of somewhat bland spindled cells with large zones of necrosis with prominent mitotic figures, changes compatible with a cellular dermatofibroma. Because the lesion exhibited clinically suspicious characteristics such as rapid growth and deep infiltration, the patient was subsequently referred to Emory for further evaluation. There was no evidence of lymphadenopathy and a chest X-ray was unremarkable.

A two-staged (five and four sections, respectively) uneventful Mohs micrographic surgery procedure was performed resulting in a defect measuring 3.5 x 3.5 x 1.0 cm. Primary closure was achieved with no complication, and the final scar measured 10 cm. Because of the suspicious clinical behavior of this tumor debulking specimen was sent for permanent section. Histopathologic interpretation of these sections was consistent with a fibrosarcoma with myofibroblastic differentiation. No clinical recurrence noted after 14-month follow-up.

Mohs micrographic surgery is a technique that has been shown to provide superior cure rates in the treatment of many mesenchymal tumors. Here, we report the first case of myofibrosarcoma treated with Mohs micrographic surgery. Myofibrosarcoma is a rare but aggressive tumor that can be difficult to distinguish from other somewhat less aggressive malignancies such as dermatofibrosarcoma protuberans or malignant fibrous histiocytoma. Specific histopathologic criteria are reviewed. We recommend including Mohs micrographic surgery in the armamentarium for the treatment of this rare tumor.