How I Treat … Apocrine Gland Anal Sac Adenocarcinomas in Dogs

Apocrine gland anal sac adenocarcinoma (AGASAC) accounts for 17% of perianal malignancies and 2% of all skin and subcutaneous tumors in dogs. AGASACs are usually unilateral, although bilateral AGASACs have been reported. The overall incidence of bilateral AGASACs, either simultaneously or temporally separated, is up to 14%. Paraneoplastic hypercalcemia is reported in 16% to 53% of dogs with AGASAC. Metastasis is common in dogs with AGASAC. Overall, metastasis is reported in 26% to 96% of dogs at the time of diagnosis, with 26% to 89% of dogs having metastasis to the regional lymph nodes (LNs) and 0% to 42% with metastasis to distant sites. The medial iliac and internal iliac LNs (collectively called sublumbar LNs) and sacral LNs are the most common sites of metastasis, while distant sites include lungs, liver, spleen, bone, and, less commonly, heart, adrenal glands, stomach, omentum, pancreas, kidneys, urinary bladder, and the mediastinum. In one study, dogs with clinical signs were more likely to have LN metastasis at diagnosis compared to dogs whose tumors were detected incidentally [...]