The ultrastructure of benign pigmented naevi and melanocarcinomas in man

Abstract

Nine benign pigmented naevi and 16 melanocarcinomas (malignant melanomas) were studied by light and transmission electron microscopy and the fine structure of benign and malignant melanocytes is described. It was found that malignant melanocytes generally exhibit a range of abnormalities of structure of nuclei and cytoplasmic organelles which distinguish them clearly 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 two types of melanosome or two types of melanocarcinoma. Although electron microscopy is capable of showing in great detail within individual melanocytes many changes which are clearly associated with malignancy, the technique does not appear to offer significant advantages over light microscopy in determining the diagnosis and prognosis in this group of conditions.

In vivo confocal microscopy of pigmented conjunctival tumors

“…Melanocytes that comprise the common acquired conjunctival nevus have a rounded polyhedral shape, manufacture abnormal, poorly melanized rounded and granular melanosomes, and only negligibly transfer melanin to the surrounding keratinocytes due to the rudimentary nature of their dendritic processes [1,4,5,7]. The nevus cells usually reside in nests aggregated at the epithelial-subepithelial junction.…”

Apurinic/Apyrimidinic Endonuclease/Redox Effector Factor-1(APE/Ref-1): A Unique Target for the Prevention and Treatment of Human Melanoma

“…Melanin synthesis represents a complex series of tightly regulated steps involving the consumption of oxygen and superoxide and the production and utilization of hydrogen peroxide, all carefully orchestrated within a well-organized organelle, the melanosome (37). Melanosomes progressively become more structurally or functionally disordered or both during melanomagenesis, evoking more ROS production and leading to an ongoing peroxide stress within the melanoma cell, especially when bound to Cu (22,28,31,96). Consistently, normal melanocytes efficiently abrogate an exogenous peroxide stress, whereas human melanoma cells are seriously impaired in their ability to do so and generate higher levels of reactive oxygen species (ROS) (74).…”

Fibrotic Melanoma in a Calf

“…In man, the lack of basal lamina around neoplastic melanocytic cells has been associated with malignancy [2]. The tumor reported here was not highly malignant; it invaded through normal tissue planes, but did not metastasize.…”