Managing canine apocrine gland anal sac adenocarcinoma

Apocrine gland anal sac adenocarcinoma (AGASAC) represents 17% of perianal tumours and 2% of all cutaneous tumours in dogs (Liptak and Turek, 2020). This tumour arises from the apocrine secretory epithelium in the anal sac gland wall (Goldschmidt and Hendrick, 2002). It is characterised by high local invasiveness and a high metastatic rate (Polton and Brearley, 2007). Furthermore, the tumour can be associated with hypercalcaemia of malignancy that causes an additional clinical challenge (Williams et al, 2003). The majority are diagnosed at a late stage, when the tumour is large and early metastasis is already established. A multimodal approach to AGASAC, including early diagnosis, surgical management, chemotherapy and radiotherapy, is associated with increased median survival time (Williams et al, 2003).

English Cocker Spaniels, Labradors and German Shepherds, followed by Cavalier King Charles Spaniels, were over-represented in a study of British dogs with AGASAC (Polton et al, 2006). Among those breeds, English Cocker Spaniels are reported to be genetically predisposed to AGASAC and have a mean relative risk of 7.3 compared to other breeds (Polton et al, 2006). The tumour tends to affect dogs in middle-to-old age, with 10 years being the median age at presentation. The risk of neoplasia increases in neutered dogs, especially neutered males (Polton et al, 2006). However, an approximately equal gender distribution has also been reported (Williams et al, 2003).