Immunohistochemical markers of melanocytic tumors.

While historically detection of premelanosomes by electron microscopic studies was the only means possible of confirming melanocytic lineage of a neoplastic process, advances in the field of immunohistochemistry have allowed for accurate and reliable diagnosis using antibodies to 1 of a number of melanocyte-restricted proteins. S-100 was the first such marker exploited by immunohistochemistry; subsequently, the HMB45 monoclonal antibody to gp100 became widely used as a sensitive and specific melanocytic marker. More recently, antibodies to other melanocytic proteins have become available, inciuding the MART-1 gene product and microphthalmia transcription factor. This article provides a brief overview of these markers in terms of their specificity and sensitivity and offers a discussion of tumors with partial melanocytic differentiation.