Neuropilin-2 as a useful marker in the differentiation between Spitzoid malignant melanoma and Spitz nevus.

Abstract

Spitzoid malignant melanoma (SMM) shares many histopathologic features with Spitz nevus (SN). The distinction between SMM and SN remains one of the most difficult diagnostic problems in dermatopathology. Neuropilin-2 (NRP2) is a cytoplasmic/cell surface protein that is a mediator of melanoma-endothelial cell interaction. The aim of this study was to evaluate NRP2 expression in SMM and SN and to determine whether it can reliably differentiate between the 2 groups. We studied the expression of NRP2 in 19 cases of SMM and 19 cases of SN from Yale Spitzoid Neoplasm Repository, New Haven, Conn. All 19 cases of SMM (100%) expressed NRP2. Most SMM showed moderate- and high-intensity staining in the majority of the melanoma cells. Most of the SN (14/19, 74%) were negative for the marker. NRP2 labeled only 5 of 19 SN (26%) and all of them demonstrated mild staining intensity. NRP2(+) staining was statistically significant in differentiating SMM from SN (P < .05). Small study size is a limitation. NRP2 expression in SMM and SN may be a useful adjunct marker, in addition to histopathologic evaluation, in the differentiation between these 2 entities.