The frequency of local recurrence and microsatellites as a guide to reexcision margins for cutaneous malignant melanoma.

A retrospective study was undertaken of local, regional, and distant recurrences in 346 patients with primary melanomas of tumor thickness less than 1.0 mm that were excised with margins of normal skin varying between 0.1 cm and 5.0 cm or more. Prospective histopathologic examination of 284 melanomas for the presence of microsatellites was also performed and their effect upon the frequency of local recurrence was studied. Margins of excision did not influence the frequency of local, regional, or distant metastases. Four recurrences of in situ superficial spreading melanoma occurred, however, when very narrow margins of excision (0.5 cm or less) were employed. Microsatellites were uncommon with tumors less than 3.0 mm in thickness (2.8% of all tumors of less than 3.0 mm in thickness, taken together), but relatively frequent in association with thicker tumors (37%). Melanomas with microsatellites were associated with a greater frequency of local clinical metastasis than those without (14% vs. 3%). Removal of more than 1.0 cm of normal skin around a melanoma of less than 1.0 mm in thickness does not further reduce rates of recurrence of any type. The use of margins of 0.5 cm or less for melanomas with a radial growth phase does appear to result in an increased frequency of local recurrence of the primary melanoma with an epidermal in situ component. These recurrences can be prevented by the removal of 1.0 cm of normal skin around such a melanoma. Microsatellites constitute a risk factor for local recurrence, but are a relatively uncommon phenomenon at tumor thickness less than 3.0 mm.