Comparative distribution of S-100 protein and antigen HMB-45 in various types of melanomas and naevi.

The content of S-100 protein and antigen HMB-45 in various types of melanomas and skin naevi was compared with respect to the frequency of two antigens, their distribution within lesions as well as diagnostic or prognostic relevance. The study material comprised 72 skin melanomas, 25 melanomas of the oral cavity and 63 non-malignant skin naevi. Formalin fixed, paraffin-embedded sections were used for immunohistochemical reactions with polyclonal rabbit anti-S-100 antibody (Dako) and monoclonal anti-HMB-45 antibody (Dianova) followed by PAP and APAAP Kits (Dianova), respectively. Detection of HMB-45 was preceded by a microwave treatment of sections. S-100 protein was found in all cases of melanomas irrespective of their location or histological type, but HMB-45 was missing in 8% of oral melanomas. Distribution of the antigens within tumors was heterogeneous and often mutually exclusive. S-100 protein was also present in all types of naevi, while HMB-45 was absent in intradermal naevi and strictly confined to epidermal component in the remaining ones. The intensity of staining for S-100 correlated inversely with the patients' survival. It was concluded that demonstration of HMB-45 might facilitate a differentiation of naevi from melanomas, whereas staining for S-100 protein might have some prognostic significance.