Abstract

The differential diagnosis between Spitz nevus and malignant melanoma is difficult due to similar histologic findings. To obtain the useful aids for the differential diagnosis between two diseases, we studied 13 cases of Spitz nevus, 8 benign nevi of compound and intradermal, and 9 melanomas of primary and metastatic, using the immunohistochemical stain for S-100 protein, HMB.45 and proliferating cell nuclear antigen(PCNA). The staining pattern and intensity of S-100 protein showed homogenously strong positive reactivity in all cases. The frequency of HMB.45 positive cell in Spitz nevus was significantly lower than that in melanoma. When compared with the usual compound and intradermal nevi, Spitz nevi showed more significantly positive reaction in the dermal component of nevus cells. The expression of PCNA was higher in melanoma than in Spitz nevus. The immunohistochemical stains for HMB.45 and PCNA are considered as a useful methods for differentiation between Spitz nevus and melanoma, while stain for S-100 protein is not helpful.

• Keywords: Spitz nevus;Immunohistochemical stain;S-100 protein;HMB.45;PCNA;