S-100 protein in amelanotic melanoma. A convenient immunocytochemical approach compared to electron microscopy

16 amelanotic melanomas were investigated immunocytochemically using two different antibodies against S-100 protein. In six cases electron microscopy was carried out. All 16 tumors showed a positive reaction for both antisera in epithelioid as well as in spindle-shaped tumor cells. Ultrastructurally the six investigated tumors contained stage II to IV melanosomes. Immunocytochemical and electron microscopical results are compared and discussed with regard to their significance in routine surgical pathology.