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Mohs Surgery with Immunostaining for Melanoma

Mohs surgery for melanoma resection is controversial, in spite of reports of high cure rates, because of its use of nonstandard margins and the difficulty of identifying intraepidermal melanoma cells on hematoxylin and eosin frozen sections. In this case series, the authors reviewed resection by Mohs surgery augmented by immunoperoxidase staining in 68 patients.

Forty-six patients had melanoma in situ, and 22 had invasive melanoma; 62 of the tumors were on the head or neck. Sections were stained with HMB-45, MEL-5, Melan-A, or a combination of stains. All but one of the tumors were excised with negative final margins; a mean of 2 stages was required. The average margin needed for tumor clearance of in situ lesions was 8 mm; 15-mm margins cleared 96 percent of these tumors. The invasive melanomas, 82 percent of which were thinner than 1 mm, required an average margin of 11 mm for clearance; 26-mm margins cleared 95 percent of these lesions. Of the 3 stains, HMB-45 was the most specific, but it stained only 85 percent of melanomas tested and failed to stain neurotropic and desmoplastic lesions. MEL-5 stained 92 percent of tumors tested, including 6 of 7 HMB-45-negative lesions, but nonspecific background and basal-layer staining made interpretation difficult in some cases. Melan-A stained 96 percent of tumors tested, with less background staining than MEL-5.

Comment: Mohs surgery with immunoperoxidase staining is helpful for thin and in situ melanomas on the head and neck, where tissue sparing is most important and local recurrence after standard excision is relatively frequent. Melan-A, sometimes augmented by HMB-45, seems to be the most useful immunoperoxidase stain for checking margins. The relatively high cost of reagents ($20 per slide) and the additional technician time may make the procedure impractical for many labs. The 5-mm margin for melanoma in situ recommended by the World Health Organization appears to be inadequate in the head and neck region. Conventional excision for thin and in situ melanomas of the head and neck should be done as a staged procedure with carefully oriented permanent sections, starting with a 5-mm margin at the first stage.

— GJ Hruza

Published in Journal Watch Dermatology August 28, 2000

Citation(s):

Zalla MJ et al. Mohs micrographic excision of melanoma using immunostains. Dermatol Surg 2000 Aug 26 771 -784.

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