The treatment for a perianal adenoma in males typically includes castration. Local resection of the mass is usually recommended as well. However, if the mass is close to the anal sphincter, or if its borders should be indistinct or diffuse, the tumor may be left surgically untreated. In these cases, resection may be considered after the mass is no longer being stimulated by testosterone and has reached a more manageable size (after several months).
The malignant version of this disease is called perianal adenocarcinoma and its considered far less common than the perianal adenoma. In most cases, perianal adenoma carries a good prognosis (after treatment, they recur in less than 10% of patients). By contrast, perianal adenocarcinoma is considered an aggressive tumor type and carries a fair to guarded prognosis.
The cost of treating perianal adenomas depends on the location and size of the tumor as well as the level of care elected and the geographic region. For most, castration and resection with a biopsy runs about $500 to $1500. For those that require additional treatments, including radiation therapy (only rarely required), treatment may cost upwards of $5,000 or more.
Radiation therapy may be elected in some cases, as may cryosurgery for small tumors (less than an inch in diameter). In some cases, administration of systemic estrogens may lead to tumor regression. However, this approach is seldom undertaken given that bone marrow suppression is considered a serious side effect of estrogen therapy in dogs.
What are the signs of these tumors?
The signs of these tumors vary depending on whether they are benign or malignant. In the case of benign perianal adenomas, you many see one or more small, round, pink, hairless, slow-growing nodules around the anus. Although they usually grow around the anus, they can grow in the prepuce, scrotum, and under the tail. Occasionally they will ulcerate (break open) and become infected. In this case, they may become irritated and painful, and you may notice your dog frequently licking the area.
Adenomas and adenocarcinomas look alike, but adenocarcinomas typically grow more rapidly and can become much larger; up to 4” (10 cm) in diameter. It is more likely that there will be multiple adenocarcinomas. Because they may also spread to the lymph nodes and underlying tissue, they can compress the rectum causing your dog to have difficulty defecating (straining) and constipation.
Adenocarcinomas can also cause a condition called paraneoplastic hypercalcemia (tumor-related high blood calcium). This condition occurs in about 30-50% of dogs with adenocarcinoma. If your dog has hypercalcemia, you may notice increased drinking and urination, loss of appetite, weight loss, lethargy, weakness, vomiting, and constipation.
Your veterinarian may suspect a hepatoid gland tumor by its typical outward appearance or by feeling a mass (or enlarged lymph nodes) while performing a rectal palpation. 35-40% of perianal adenocarcinomas are found incidentally via rectal palpation, with no outward signs of disease.
The diagnosis of a suspected tumor requires a microscopic examination of the tissue. Your veterinarian may use one or more methods of obtaining a tissue sample for diagnosis. The most common methods include fine needle aspiration (FNA), biopsy, or full excision of the tumor.
Fine needle aspiration (FNA) involves taking a small needle with a syringe and suctioning a sample of cells directly from the tumor and placing them on a microscope slide. A veterinary pathologist then examines the slide under a microscope. In some cases, results from FNA may not be entirely clear and a biopsy may be necessary. A biopsy is a surgical excision of one or more pieces of the tumor. The pieces are then examined by a veterinary pathologist under the microscope. This is called histopathology. Histopathology is not only helpful to make a diagnosis but can indicate how the tumor is likely to behave. Alternatively, the tumor may be fully excised and sent for histopathology.
How does this cancer typically progress?
Perianal adenomas typically grow slowly and only to a certain size, usually less than 1 inch (3 cm). Epitheliomas behave like adenomas except that they may infiltrate the surrounding tissues. Adenomas and epitheliomas are prone to ulceration and infection.
Perianal adenocarcinomas typically grow rapidly, invade the underlying tissues, and can spread (metastasize) to the local lymph nodes, abdominal organs, and lungs. Tissue invasion and lymph node involvement can lead to difficulties with defecation. Metastasis to the other organs can damage these organs, and lead to systemic illness, lethargy, and weight loss. Staging (searching for potential spread to other locations in the body) is highly recommended for adenocarcinomas. This may include bloodwork, urinalysis, radiographs (X-rays) of the lungs, and possibly an abdominal ultrasound. If any lymph nodes are enlarged or feel abnormal, further sampling may be pursued to determine if spread is present.
What does perianal adenocarcinoma look like?
Is perianal adenoma painful?
How long do dogs live with perianal adenocarcinoma?
What is a perianal gland tumors?