MART 1 (MLANA) is a protein antigen present on the surface of melanocytes that is involved in melanosome biogenesis by ensuring the stability of GPR143. It plays a vital role in the expression, stability, trafficking, and processing of melanocyte protein PMEL, which is critical to the formation of stage II melanosomes. Antibodies to MART1 are used to distinguish melanocyte differentiation and to diagnose melanomas. In immunohistochemistry, it is positive in melanocytes, steroid-producing cells in the adrenal cortex, testis and ovary. In cancer, it is positive in melanomas, granulosa cell tumors, adrenocortical carcinomas, Sertoli-Leydig cell tumors of the ovary and testis, and angiomyolipomas. References: Am J Surg Pathol. 1998.22:976, PMID: 9706977; Proc. Natl. Acad. Sci. U.S.A. 1994 Apr. 91 (9): 3515–9, PMID: 8170938; Arch Pathol Lab Med. 2011;135:853–859, PMID: 21732774