MART-1/Melan A

MART-1, also known as Melan A, is a melanoma-associated antigen recognized by autologous cytotoxic T lymphocytes 1-4. MART-1 and Melan A are synonyms. Currently there are two antibodies/clones that are commercially available: A103 and M2-7C10. Immunohistochemical studies have shown MART-1/Melan A expression in all (100%) dysplastic, junctional, intradermal, compound, Spitz, and congenital nevi, as well as in lymph node capsular nevi. It is also expressed in most primary and metastatic melanomas. The percentage of MART-1/Melan A expression has ranged from about 85% to 97% for primary melanomas and from 57% to 92% for metastatic melanomas. In a combined review of 1183 metastatic melanomas from 12 published series, the sensitivity of MART-1/Melan A IHC detection has reached up to 86% (976 of 1183 cases). Desmoplastic melanomas have been reported often to be negative for this marker. In a combined review of 99 cases from 9 published studies, only 7 of 99 cases (7%) of desmoplastic melanoma were reported to be MART-1/Melan A positive. Because of its high sensitivity for melanoma, MART-1/Melan A is considered a useful marker for the identification of micrometastases in sentinel lymph nodes. It has the advantage over S100 in that MART-1/Melan A is not expressed in dendritic cells and histiocytes in lymph nodes, which makes the interpretation of the immunostaining in sentinel lymph nodes much easier. In addition, when compared with HMB-45, it appears to be more sensitive.