The ultrastructure of benign pigmented naevi and melanocarcinomas in man

Abstract

Nine benign pigmented nevi and 16 melanocarcinomas (malignant melanomas) were studied by light microscopy and transmission EM, and the fine structure of benign and malignant melanocytes is described. Malignant melanocytes exhibit a range of abnormalities of structure of nuclei and cytoplasmic organelles which distinguish them from their benign counterparts. Of the abnormalities, those affecting the specific organelle of the melanocyte, the melanosome, were the most constantly present. No firm evidence was found for the existence of 2 types of melanosomes or 2 types of melanocarcinomas. Although EM is capable of showing in great detail many changes which are associated with malignancy in melanocytes, the technique does not appear to offer significant advantages over light microscopy in determining the diagnosis and prognosis in this group of conditions.