Melan-A expression in non-melanocytic carcinoma: A potential diagnostic pitfall

. Background. Melan-A/MART-1 is a melanocytic differentiation marker recognized as an antigen on melanoma cells. It is a useful diagnostic marker for pathologists in the diagnosis of melanocytic tumors. However, we recently found that Melan-A can be expressed in some non-melanocytic carcinomas that are rarely reported in the literature. Methods. We analyzed the expression of Melan-A in immunohistochemistry. Marker positivity was defined as Results. In 87 non-melanocytic carcinoma tissue samples, Melan-A was positive in six (6.89%) cases, of which four (66.7%) were male and two (33.3%) were female, with a mean age of 60 years (range 21-82 years). Five (83.3%) of the Melan-A-positive cases had distant metastases. Compared with Melan-A negative cases, Conclusions. Melan-A expression is relatively rare of melanoma, urges pathologists to exercise caution in cases of Melan-A positivity, and illustrates the need for misdiagnosis.