Desmoplastic malignant melanoma: study of a case by light and electron microscopy.

This article is a study by light and electron microscopy of a case of desmoplastic malignant melanoma that attempts to resolve the conflict in views regarding the nature of the cells responsible for the desmoplasia associated with this clinico-pathologic entity. On the basis of evidence presented, it is concluded that the cells are dedifferentiated cells of the malignant melanoma with fibroblastic features and probably fibroblastic functions rather than host-engendered fibrolbasts in response to invasive melanoma. The evidence consists of the finding of macular desmosomes between those cells, a feature previously noted in amelanotic and melanotic melanomas, the finding of others by electron microscopy of fibroblast-like cells in spindle-cell squamous carcinomas, and the finding by light microscopy of features of vascular invasion of the malignancy. That the diagnosis of this variant of malignant melanoma by pattern can be made by light microscopy is reaffirmed.