Apocrine Gland Anal Sac Adenocarcinoma in Dogs: 22 Cases (2015-2020)

Background: Apocrine gland anal sac adenocarcinoma (AGASACA) is a highly malignant disease mostly invading regional lymph nodes at the time of disease diagnosis.Methods: Twenty- two cases of Apocrine gland anal sac adenocarcinoma (AGASACA) were treated during five years. Contrast radiography with Iohexol and Lipidol were carried out to detect primary anal sac mass and regional lymph node through indirect lymphography technique. For clinical staging, ultrasonography, fine-needle aspiration cytology, histopathology of both primary tumor mass and regional lymph node were performed. Closed anal Sacculectomy was performed as curative therapy for anal sac adenocarcinoma.Result: The median age and weight of dogs at presentation were 8.4 years and 20.9 kg, respectively. Diagnostic radiology, histopathology and biochemical assay confirm twenty-two cases of anal sac adenocarcinoma and medial iliac lymph node to be sentinel lymph node. Carcinoma was of unilateral occurrence in all the dogs. Four (18%) dogs had hypercalcemia and twelve (54%) had metastases to the regional lymph nodes with clinical signs of tenesmus or constipation, polyuria -polydipsia and anorexia. Apocrine gland Adenocarcinoma of anal sac was found to initially metastasize to the medial iliac lymph node. Survival times of dogs treated with the surgical procedure only (8 out of 22 dogs) were appreciably longer than the dogs with therapeutic only. Animals with metastasis to regional lymph nodes or lymphadenopathy had poor prognosis.

Collision tumour of two nodal metastases (adenocarcinoma and mast cell tumour) in a dog

An 11-year-old female neutered Labrador retriever was referred for a large vulvar mast cell tumour that extended into the vagina. Abdominal ultrasound revealed an enlarged right medial iliac lymph node, and cytology of the node was consistent with an endocrine/neuroendocrine tumour. An approximately 1.5-cm right anal sac mass was palpated. Medial iliac lymphadenectomy via ventral celiotomy, right anal sacculectomy and marginal vulvar mass resection were performed. Histopathology was consistent with right anal sac adenocarcinoma, vulvar mast cell tumour, and the right medial iliac lymph node showed a metastatic collision of both the adenocarcinoma and mast cell tumour cell populations. Adjunctive chemotherapy and radiotherapy were recommended to address the risk of local recurrence and further metastasis but were declined by the owner. The dog remains alive and asymptomatic with no visible evidence of recurrence 14 months after initial presentation.