Surgical margins for melanoma in situ

BackgroundA controversy in the treatment of melanoma in situ is the required width of surgical margin. The currently accepted 5-mm margin is based on a 1992 consensus opinion, despite data since then showing this is inadequate.ObjectiveWe sought to develop guidelines for predetermined surgical margins for excision of melanoma in situ.MethodsA prospectively collected series of 1072 patients with 1120 melanoma in situs was studied. All lesions were excised by Mohs micrographic surgery with frozen-section examination of the margin. The minimal surgical margin was 6 mm, and the total margin was calculated by adding an additional 3 mm for each subsequent stage required. The minimum surgical margin that would successfully remove 97% of all tumors was calculated. Local recurrence was also tabulated.ResultsIn all, 86% of melanoma in situs were successfully excised with a 6-mm margin; 9 mm removed 98.9% of melanoma in situs. The superiority of 9-mm to 6-mm margins was significant (P < .001). Gender, location, and diameter did not affect results. Recurrence rate for this set of patients treated with Mohs micrographic surgery was 0.3% (n = 3).LimitationsMargins less than 6 mm were not studied. This is a referral center for melanoma in situ and 10% of tumors were previously treated before presentation to our clinic.ConclusionThe frequently recommended 5-mm margin for melanoma is inadequate. Standard surgical excision of melanoma in situ should include 9 mm of normal-appearing skin, similar to that recommended for early invasive melanoma.