DIAGNOSTIC-ASSESSMENT OF 2 NOVEL PROLIFERATION-SPECIFIC ANTIGENS IN BENIGN AND MALIGNANT MELANOCYTIC LESIONS

The aim of this study was to gain a thorough insight into the prolifer ative activity of benign and malignant melanocytic tumors. A total of 314 cases were examined by immunohistochemistry on paraffin-embedded m aterial. The growth fraction was assessed by means of two monoclonal a ntibodies, Ki-S1 and Ki-S5, which react with two different proliferati on-specific nuclear antigens. Additionally, HMB-45 was used as a marke r of melanocytic activation. Statistically significant differences (P < 0.01) in the proliferation rates were found between common acquired nevi, Spitz's/Reed's nevi, primary cutaneous melanomas, and metastatic melanomas, whereas dysplastic nevi were hardly distinct from other ne vi of the compound type. In melanoma, the growth fraction correlated w ell with the tumor stage but poorly with HMB-45 expression and mitotic count. Along with tumor progression, an increasing heterogeneity of p roliferation indices was observed. Our results provide no evidence for a progression from dysplastic nevi into melanoma. They indicate that the assessment of the proliferative activity may be of considerable di agnostic help in cases of uncertain histology and that it might contri bute to an alternative concept for the classification of melanocytic t umors.