Melanocytic matricoma. Report of a further case with clinicopathological and immunohistochemical findings, differential diagnosis and review of the literature

Melanocytic matricoma is a rare recently described lesion. It usually presents as a pigmented, dark-papular, crusted lesion on sun-damaged skin of adult patients. Histopathologically, these lesions are characterized by well-circumscribed nodules composed of matrical and supramatrical cells with clustered shadow cells, and admixed pigmented dendritic melanocytes. It differs from matricomas and pilomatricomas by its lack of calcification, cyst formation, granulomas, and connections to the epidermis and other adnexal structures. The clinical differential diagnosis includes hemangioma, pigmented basal cell carcinoma, and melanoma. Melanocytic matricoma presumably is the representation of an epithelialmelanocytic interaction in the anagen phase of the hair cycle. An extensive search of the medical literature revealed 11 reports of benign melanocytic matricomas and 5 malignant counterparts. We report an additional case of melanocytic matricoma with discussion of clinicopathologic features and differential diagnosis.