Mohs micrographic excision of melanoma using immunostains

BACKGROUND. Mohs excision of melanoma remains controversial, in part becaus e of concerns regarding evaluation of frozen section margins. Several immun ohistochemical stains are available for melanoma that can be used on frozen sections. OBJECTIVE. To review our experience with Mohs micrographic excision of mela noma using immunostains. METHODS. Sixty-eight patients were treated, including 46 with melanoma in s itu and 22 with invasive melanoma, 62 of which were on the head or neck. HM B-45, MEL-5, Melan-A (A-103), and S-100 stains were employed. RESULTS. Sixty-seven of 68 tumors were excised to clear margins, requiring an average of 2.0 layers. Immunostains greatly enhanced detection of melano ma on frozen sections. The average margin required for clearance of in situ melanoma was 8.3 mm and of invasive melanoma was 11.1 mm. Only 23 of 46 (5 0%) in situ melanomas were clear with less than or equal to 6 mm margins; 1 5 mm margins were required to clear 96% of the tumors. Eleven of 22 (50%) i nvasive melanomas were clear with less than or equal to 6 mm margins; 26 mm margins were required to clear 95% of the tumors. Melan-A (A-103) was the most consistently crisp and easily interpreted immunostain. CONCLUSIONS. MOhs excision of melanoma using immunostains can be useful, es pecially for tumors on the head and neck. For routine excision, margins wid er than those currently recommended may be required to ensure tumor clearan ce. We recommend that (1) biopsies be stained preoperatively for Melan-A an d/or HMB-45, (2) a debulking layer be obtained for permanent sections prior to Mohs layers, and positive and negative control specimens from the tumor and distant skin should be employed for comparison of staining patterns. L arge-scale prospective studies of in situ and invasive melanoma on the head and neck are necessary.