Anal sac adenocarcinoma (AGASAC) is an uncommon tumour in the dog and comprises approximately 17% of perianal malignancies; however, it is one of the most common causes of paraneoplastic hypercalcemia. Clinical signs in affected dogs most commonly are associated with mechanical obstruction caused by the primary tumour or enlarged regional metastatic lymph nodes and the effects of paraneoplastic hypercalcemia when present. Surgical excision of the primary tumour and metastasectomy of affected locoregional lymph nodes is the preferred initial treatment option for most dogs, although radiation therapy and adjuvant chemotherapy are commonly incorporated into multi-modality treatment plans. Prolonged survival times are possible, especially for dogs with smaller primary tumours and for dogs that undergo further treatments for recurrent disease.

In this lecture, we will discuss the clinical signs, diagnosis, staging, treatment, and prognosis of AGASAC in the dog