The MART-1/Melan-A recognizes a protein of 18 kDa, identified as MART-1 antibody (Melanoma Antigen Recognized by T cells 1) or Melan-A. MART-1 antibody recognizes a subcellular fraction found in melanosomes. The antibody labels melanomas and tumors showing melanocytic differentiation. It does not mark neoplasms of epithelial origin, lymphomas or mesenchymal tumors. MART-1 is a useful addition to melanoma panels which are specific to melanocytic lesions. MART-1 is coexpressed with HMB45 in the majority of melanomas, as well as solely expressed in certain cases. Studies have shown that MART-1 is more sensitive than HMB45 when labeling metastatic melanomas.