Immunohistochemistry in melanocytic lesions: Updates with a practical review for pathologists

This review provides a summary of the immunohistochemical markers pertinent to the diagnosis of melanocytic lesions. There is considerable morphologic overlap between benign and malignant melanocytic lesions, and given the significant differences in clinical management, the diagnostic workup becomes crucial. Immunohistochemistry aids in the distinction between various melanocytic proliferations and recent contributions to the literature have furthered our optimization of panels in the diagnostic workup. In recent years, SOX10 has been considered as the optimal marker for melanocytic lesions given the similar sensitivity but higher specificity than S100. HMB-45 is less sensitive than S100 but demonstrates utility in confirmation of deceptively banal small cell and nevoid melanoma variants where deep nests of melanocytes are highlighted. Melan-A (MART-1) and MiTF show similar sensitivity to S100 however there is a lack of expression in spindle cell and desmoplastic melanomas.