Juvenile melanoma--a case report and histogenetic investigation.

A case of juvenile melanoma which appeared to be completely intradermal was studied by optical and electron microscopy. The histological dopa reaction was negative and melanin granules could not be detected with Fontana-Masson stain, but detailed electron microscopic examination revealed melanosomes very similar to those found in intradermal nevus cells. The tumor was therefore thought to be composed exclusively of melanogenic nevus cells, and participation of schwannian nevoblasts could be excluded. This view would support the concept of the unitary origin of such nevus cells.