Presence of fibroblast-type intermediate filaments (vimentin) and absence of neurofilaments in pigmented nevi and malignant melanomas.

The cytoskeletal intermediate filaments of pigmented nevi and malignant melanomas (nine cases of each) were evaluated using monospecific antibodies against intermediate filament proteins and immunofluorescence microscopy. Both pigmented nevi and cutaneous malignant melanomas showed only vimentin-type intermediate filaments, but not keratin, neurofilaments, desmin or glial fibrillary acidic protein. Thus, nevi and melanomas do not show neural characteristics in the cytoskeletal intermediate filament pattern although they appear to show other neural markers. Vimentin - content in melanomas versus keratin - content in carcinomas may be used as a differential diagnostic feature.