A Canine Case of Mixed Carcinoma of the Sweat Gland in the Footpad

A 9-year-old, castrated male mongrel dog had a mass in the footpad of the left hindlimb. Histologically, the tumor was composed of irregular tubuloacinar structures with desmoplasia, and apocrine secretion was observed on the surface of the neoplastic glands. Several neoplastic foci comprised of the cuboidal to polygonal epithelial cells showing a glandular proliferation and the spindle-shaped neoplastic cells proliferating adjacent to chondroid matrix. The epithelial cells showed a nuclear atypia and frequent mitotic activities. The epithelial cells were immunohistochemically positive for cytokeratin (AE1/AE3 and cytokeratin 8). The spindle-shaped cells showed intense immunoreactivity for vimentin but not for cytokeratins and smooth muscle actin. The tumor was diagnosed as mixed type of adenocarcinoma of sweat gland. Multifocal metastatic masses were observed in the lung 6 months after surgery.