A case of halo nevus with effete melanocytes.

Epidermal melanocytes in the depigmenting lesion were examined in one typical case of halo nevus. Vacuolated melanocytes found in the upper layers of epidermis were not, as observed in serial sections, connected to the basal lamina. These melanocytes contained individual as well as aggregated melanosomes in what appeared to be autophagosomes. Part of the cytoplasm of these melanocytes appeared condensed and segregated and their nuclei were often pyknotic. These melanocytes were considered to be degenerated cells which had been detached from the basal layer and were being shed from the skin. Although epidermal keratinocytes, particularly basal cells, were also vacolated. Langerhans cells and non-specific dendritic cells were more or less intact. The total number of these dendritic cells seemed to be increased.