Immunohistochemical characterization of Spitz's nevus: differentiation from common melanocytic nevus, dysplastic melanocytic nevus and malignant melanoma.

Abstract

AbstractRecently it has been reported that Spitz's nevus possesses a deranged melanogenesis with formation of the spherical melanosomes also seen in superficial spreading melanoma (SSM) and dysplastic melanocytic nevus (DMN). To characterize the nature of Spitz's nevus, immunohistochemical studies were carried out in 9 cases of this condition using monoclonal antibodies (MoAbs) which identify (a) human melanosome‐associated antigen (HMSA‐1 and HMSA‐2), (b) S‐100 protein (α and β subunits), (c) Leu‐7 (HNK‐1), (d) β2 microglobulin (B2MG), and (e) neuron specific enolase (NSE). In contrast to SSM and DMN, none of the 9 cases showed any significant reactivity with MoAbs HMSA‐1 and HMSA‐2. Similar to cutaneous malignant melanoma (CMM) and DMN, and unlike common melanocytic nevus (CMN), anti‐S‐100 protein α subunit MoAb reacted from moderately to intensely with Spitz's nevus, and anti‐S‐100 protein β subunit MoAb reacted weakly. Anti‐B2MG MoAb was reactive with 8 of 9 cases. Only one case showed cytoplasmic reactivity to anti‐Leu‐7 MoAb. Polyclonal NSE was found in 7 cases at varying intensities. Our immunohistochemical study indicates the distinct, benign neoplastic nature of Spitz's nevus which has immunoreactivities differing from those of CMM, DMN and CMN.