Desmoplastic melanoma: comparison of expression of differentiation antigens and cancer testis antigens

Desmoplastic melanoma is a diagnostic and therapeutic challenge. Immunohistochemical analysis with antibodies to melanoma antigens can complement morphologic evaluation. Although staining for S100 protein is generally positive, staining for other melanoma differentiation antigens, particularly gp100, Melan-A/MART1 and tyrosinase, is often negative despite being commonly positive in other melanoma types. A high clinical index of suspicion and better diagnostic techniques are essential as atypical features and incorrect diagnosis can lead to poor clinical outcomes. Antigens associated with melanoma, such as the melanocyte differentiation and cancer testis antigen, may become important targets for immune therapies. We characterized the patterns of antigen expression of desmoplastic melanoma from 32 patients, including gp100, Melan-A/MART-1, tyrosinase, MAGE-A1, MAGE-A4 and NY-ESO-1. Consistent positive staining with S100 was observed. Differentiation antigens were expressed more frequently than cancer testis antigens regardless of the histological subtype of desmoplastic melanoma. When present, cancer testis antigen expression correlated to positive staining with differentiation antigens. The diagnostic yield of desmoplastic melanoma did not increase with the addition of cancer testis antigen typing. Low levels of expression of cancer testis antigen may indicate that they are suboptimal targets for vaccine development in desmoplastic melanoma.