Matrical carcinoma with prominent melanocytic hyperplasia (malignant melanocytic matricoma?) A report of two cases.

Melanocytic matricoma is a recently described lesion characterized by well-circumscribed nodules composed of matrical and supramatrical cells with clustered ghost cells, and admixed pigmented dendritic melanocytes, with no cyst formation or connection to the epidermis or pre-existing hair follicles. Although variable cytologic atypia and frequent mitoses in the epithelial component may be present, given the well-defined margins and absence of tumor recurrences, these lesions were initially considered benign neoplasms, and not matrical carcinoma. Theoretically, the detection of numerous melanocytes in matrical carcinoma should not be surprising, but is in fact a very unusual feature. A case with extensive melanization of epithelial elements and only rare melanocytes has been reported. We report two cases of matrical carcinoma with prominent melanocytic hyperplasia, with emphasis on the ultrastructural and immunohistochemical features. Our cases might be considered the malignant counterpart of the so-called melanocytic matricoma.