Perianal Adenoma in Dogs

Perianal Adenoma in Dogs

Perianal adenoma (or circumanal adenoma) is a benign tumor arising from sebaceous glands that surround the anus. 80% of perianal tumors are of this type, and although it is not a true cancer, it would be classified as a perianal adenocarcinoma if it were. This type of tumor is particularly common in intact male dogs, and seems to be fueled by testosterone. Therefore, castration is often an integral part of treatment for perianal adenoma.


Perianal adenoma in dogs is a malignant tumor that forms around the anus. These tumors are highly sensitive, and can be quite painful for your dog. However, there are ways to tell the difference between benign and malignant tumors. A dog with a perianal adenoma may show small, hairless nodules in the anus or under its tail. Symptoms of perianal adenoma in dogs include pain, irritability, and frequent licking of the painful area.

Perianal adenomas in dogs are usually diagnosed through biopsy, as simple cell analysis is not reliable enough to differentiate benign from malignant tumors. The symptoms of perianal adenoma in dogs vary according to breed, but some breeds are predisposed to the development of these tumors. In general, however, male dogs are more likely to develop perianal adenomas than females.


Perianal adenoma is a cancer that arises from the anal sac. It usually affects older dogs, although it is also found in younger animals. The symptoms may be nonspecific, including tenesmus or perineal swelling. One third of the animals affected by this cancer will exhibit no clinical signs. A biopsy sample and cytology are required to confirm the diagnosis.

Perianal tumors are often diagnosed incidentally during a routine rectal examination. They may range in size from small to large before clinical signs emerge. The most common symptoms include increased drinking and urination, and straining to defecate. In large tumors, the tumor may enlarge regional lymph nodes that press against the colon. Depending on the stage of the tumor, surgery may be necessary.

Benign perianal adenomas in dogs may be self-limited and cause no symptoms at all. A few symptoms of perianal adenoma include pain and anal irritation. Sometimes, these tumors may be ulcerated or necrotic. A vet may recommend surgical removal if the mass is causing an ulcer or bleeding. However, it is always best to seek medical attention right away.

Treatment options

Treatment options for perianal adenema in dogs may include surgical removal of the tumor, a course of radiation therapy, or chemotherapy. Although the prognosis for untreated perianal adenoma is poor, complete removal of the tumor can prolong the life of the dog and keep him comfortable. A veterinarian may prescribe antibiotics to treat any ulcerated tumors.

Conservative resection and castration of a perianal adenoma in a healthy male are effective for small tumors. However, recurrences of the mass may require biopsies in order to rule out an adenocarcinoma. Unfortunately, approximately 15% of dogs with perianal adenoma will have metastatic disease by the time of diagnosis. However, aggressive saline diuresis and treatment of hypercalcemia should continue prior to surgery.

In intact male dogs, 80% of perianal adenomas are benign. Surgical removal is not necessary in small tumors, although large adenomas may be removed. In male dogs with multiple tumors, neutering should be performed before any surgical removal. Once the dog is neutered, the tumor will shrink and not require further treatment. If the adenomas are located near the anal sphincter, it may be best to wait several months before removing them. A reduction in testosterone will make the tumor shrink.


Although the prognosis of perianal adenomas in dogs is generally good, it does depend on some factors. Tumor size, presence of metastasis, and hypercalcemia on blood work are associated with a more guarded outlook. Dogs with tumors of 10cm2 or larger had a median survival time of nine months. Dogs with smaller tumors lived an average of 19 months.

Perianal adenomas are relatively common in intact male dogs. If found early enough, they often regress on their own without surgery. However, if they are large or near the anal sphincter, a neutering procedure may be necessary. Waiting a few months after detection can also improve the prognosis. Perianal adenomas will shrink when the hormone testosterone is blocked. Neutering male dogs can help a patient’s prognosis by eliminating perianal adenomas.

AGASACA is a common form of perianal adenoma, accounting for approximately 17% of perianal malignancies. AgASACA usually presents with no clinical signs or symptoms but can cause hypercalcemia and polyuria. Patients with this tumor may need surgical resection, which can be effective for long-term control. The average age at diagnosis is nine to eleven years.

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