Pilomatrix carcinoma. A case report with immunohistochemical findings, flow cytometric comparison with benign pilomatrixoma and review of the literature.

We report a case of pilomatrix carcinoma in a 42 year old woman. The patient presented a rapidly growing 4-cm subcutaneous mass in the right preauricular area. She was free of recurrence 24 months after surgery. Immunoreactivity was studied for cytokeratins, epithelial membrane antigen, S-100 protein, blood group antigens, Leu-M1, beta-2-microglobulin, vimentin, neuron-specific-enolase and cellular binding for peanut agglutinin. Squamous cells were reactive for cytokeratin AE1/3, epithelial membrane antigen, blood group antigens B and H, and peanut agglutinin. Basaloid cells were focally reactive for cytokeratin AE1/3 and epithelial membrane antigen. Flow cytometry revealed a euploid DNA content and a high proliferative rate of the pilomatrix carcinoma and in benign pilomatrixoma studied for comparison. The pathological diagnosis must be based on histomorphological criteria.