Sweat gland carcinoma with mucinous and infiltrating duct-like patterns

We report a rare case of mucinous carcinoma of the skin with mammary infiltrating carcinoma-like patterns. An 82-year-old Japanese male had a gourd-shaped tumor on his scalp. Histopathologically, the posterior portion of the tumor showed small lobules of cuboidal tumor cells with no atypia floating in mucinous lakes. In the anterior portion, there were solid lobules, cords, and strands of anaplastic tumor cells infiltrating into the surrounding stroma. Enzyme- and immunohistochemistry and electron microscopy confirmed the eccrine origin of this tumor. It is suggested that mucinous carcinoma of the skin can occur in association with diverse histological patterns, analogous to mucinous carcinoma of the breast.