A case of malignant melanoma expressing epithelial cell markers in immunohistochemistry using paraffin sections

: Recently, applications of immunohistochemical techniques for the cytoplasmic localization of intermediate filaments has produced advances in tumor diagnosis and characterization. We report a 58-year-old white male with a clinically and histologically typical metastatic malignant melanoma. This case was peculiar because the same neoplastic cells stained for both S-100 protein and keratin on paraffin embedded tissue. These facts illustrate how cautiously we must interpret the positivity of immunohistochemical technics. We thus insist on the importance of the clinical and basic histologic data for the diagnosis, in order to avoid errors.