Perianal (circumanal) glands are modified sebaceous glands unique to the dog. Perianal adenoma development is driven by testosterone therefore these tumors are common in older intact male dogs. It is a common tumor that can occur anywhere around the anus and base of the tail, but it is usually found perianally.

Perianal gland adenomas include more than 80 % of all perianal tumors in dogs. They are rare in cats, most likely because cats do not have perianal glands. Perianal adenomas are 12 times more likely to occur in male intact dogs than in female. Female dogs develop these tumors rarely and mostly affect spayed females. The most commonly affected breeds are the Siberian Husky, Cocker Spaniel, Pekingese, and Samoyed.

Usually the tumors are small, well circumscribed, and are often incidental findings. However with time, they may become extremely large, ulcerate, and bleed or become secondarily infected. The most commonly affected breeds are the Siberian Husky, Cocker Spaniel, Pekingese, and Samoyed.

Clinical signs and Diagnosis
Animals with these tumors may show no clinical signs, but anal irritation and discomfort can occur, especially if the tumor is ulcerated. Other signs may include straining to defecate, constipation, and swelling or pruritus of perianal area.
Physical examination most commonly reveals a swelling or mass in the perianal area. The mass may be pedunculated, ulcerated, and/or necrotic. Diagnosis is usually made by taking a fine needle aspirate or biopsy.

In intact males, the preferred treatment is castration with excision of the tumor. Although these tumors generally regress with castration, surgical excision helps to prevent recurrence. Estrogen therapy has been used in cases when tumors do not regress with castration or in animals too debilitated for surgery, but estrogen therapy carries with it the risk of life threatening bone marrow suppression. Cryosurgery has been used in some cases with good results, but may result in anal strictures and incontinence. The client should be warned that the procedure is smelly and messy. Castration eliminates the major source of testosterone. Generally, neutering male dogs early in life will help prevent the development of perianal adenomas and other such growths.

Prognosis after resection is good.