Context: Histologic analysis allows accurate classification of most melanocytic lesions as benign or malignant. Only in a minority of lesions is it necessary to use other techniques as an aid in the diagnosis. Among them, most authors recommend immunohistochemistry.
Objective: To describe how to apply immunohistochemistry to particular differential diagnoses and the potential pitfalls.
Data sources: Personal experience and review of literature.
Conclusions: There is no single marker, or combination thereof, that establishes an unequivocal diagnosis of melanoma or nevus. Thus it is necessary to carefully analyze the pattern of expression (patchy versus diffuse) and localization (maturation) in the context of morphologic standard features.