Clinicopathological Features of Apocrine Sweat Gland Carcinoma Treated with Surgical Excision in Five Dogs

The clinicopathological features of apocrine sweat gland carcinoma in five dogs were evaluated. All five dogs were ≥12 years old and had a solitary lesion with ulceration due to tumor invasion into the epidermis. Glandular formation, desmoplasia, and stromal invasion were histopathologically observed in all cases. Two dogs also had features of scirrhous carcinoma. Wide tumor excision resulted in good local control in all dogs, but one with scirrhous carcinoma (interdigital forelimb tumor) developed metastasis to a superficial lymph node 3 months after surgery. Another dog with scirrhous carcinoma (tumor fixed to the elbow) with vascular invasion died of widespread skin metastasis 6 months after surgery. The dog with the highest mitotic index (tumor near the vagina) died of multiorgan metastases 7 months after surgery. The other two dogs showed no metastasis during the follow-up period. Wide excision may be useful for local control of apocrine sweat gland carcinoma in dogs; however, the metastatic potential should be considered in some dogs with histological features of scirrhous carcinoma, a high mitotic index, or vascular invasion.