No abstract

No abstract

No abstract

No abstract

Six cases of demoplastic melanoma were studied by light and elctron microscopy. The tumors fulfilled one or more of the following criteria: (1) having the presence of atypical intraepidermal melanocytic proliferation bordering the primary lesion; (2) an antecedent history of melanoma at the site of recurrence; (3) a metastatic lesion in the direct lymphatic drainage route of a previously excised melanoma. Premelanosomes were not identified in the neoplastic cells. Ultrastructural features common to the six tumors were interpreted as evidence of Schwann cell differentiation, i.e., neurosarcomatous transformation occuring in malignant melanoma. The ultrastructural findings provide further support for the concept that melanocytic lesions may simulate tumors of Schwann cell origin, presumably reflecting the common embryologic origin of the two cell types from the neural crest.