Primary mucinous carcinoma of the skin.

Primary mucinous carcinomas of the skin are very rare. To date, 120 cases have been described in the literature. This tumor is a histologic subtype of sweat gland carcinoma. Because of the histopathologic appearance, primary mucinous carcinoma of the skin can be mistaken for metastasis from extracutaneous sites. We report on the cases of two elderly women with mucinous carcinomas arising in the scalp. Immunohistochemical staining of both tumors was positive for low-molecular-weight cytokeratin and epithelial membrane antigen. Carcinoembryonic antigen was positive in Case 2. Neuroendocrine features represented by neuron-enolase-specific positivity were also observed in both cases, and Grimelius and chromogranin A positivity were observed in Case 2. In both cases, there was strong positivity for estrogen receptor and progesterone receptor. Image analysis cytometry showed a diploid DNA content with a low rate of proliferative cells and negativity for p53 and c-erbB-2 proteins in agreement with the low aggressiveness of these neoplasms.