A specific melanoma antigen protein derived from a patient (NA17) with cutaneous melanoma metastases. When administered in a vaccine formulation, NA17-A antigen may stimulate a cytotoxic T lymphocyte (CTL) response against tumors that express this antigen, which may result in a reduction in tumor size. The NA17-A antigen is part of the enzyme N-acetyl glucosaminyl-transferase V (GnT-V). Approximately half of melanomas have been found to express significant levels of this atypical protein, which is not expressed by normal tissues.