Malignant melanoma in the lower extremity. A comprehensive overview.

Malignant melanoma has been on the rise in recent years. Melanomas account for 1 per cent of all cancers in the United States and mortality rates are doubling every 10 to 17 years. Lower extremity melanomas are more common in females and have been reported as the most common malignant skin tumor of the foot. Etiology is still unclear, but sunlight, hormonal, genetic, and immunologic factors all have been implicated. Diagnosis is made on suspicious lesions by appropriate biopsy, usually in the form of an excisional biopsy for pathologic identification and staging. Margins for excisional biopsy need only to include a few millimeters of healthy skin and can be closed primarily. It is important to include subcutaneous fat in the specimen. Prognosis is based on the type of melanoma, anatomic site, and clinical and pathologic stage. Stage I thin melanomas have good survival rates with few local recurrences, and re-excision of the biopsy site with 1- to 2-cm margins is usually sufficient treatment. Melanomas that are 0.76 to 4.0 mm require 3-cm margins. Those over 4.0 cm require a 5-cm margin of excision. Subungual melanomas usually require amputation and plantar lesions usually require split-thickness skin grafts if primary closure cannot be performed. Level IV and V melanomas with nodal metastases require therapeutic lymph node dissection. Level III lesions 1 to 4 mm in thickness have a 20 per cent incidence of nodal metastases and prophylactic lymph node dissection may benefit these patients, especially if ulceration is present clinically. Those patients with melanomas that have a poor prognosis may have improved survival with some form of adjuvant treatment.