Perianal Gland Tumor in Dogs

The presence of a perianal gland tumor is usually not painful for your dog, but it can cause your dog to pay a lot of attention to that area. While these nodules can grow without any symptoms for months or years, they can eventually rupture and bleed, leaving your dog susceptible to infections. Tumors may appear as single or multiple masses in the anal area, and can create a thickened ring around the anus. Signs include:

• Round, nodules in the skin near anus
• Thickened ring of tissue surrounding anus
• Bleeding nodules
• Excessive licking of the anal area
• Scooting rear end on ground
• Colorectal obstruction 
• Rectal pain
• Protruding rectal mucous membrane 
• Straining to defecate 
• Bloody feces 
• Vomiting blood
• Increased thirst
• Increased urination 
• Decreased appetite
• Lethargy
• Reduced exercise tolerance 
• Growth on the testes
• Hypercalcemia, or elevated blood calcium levels

Types

• Perianal gland tumors are categorized as benign adenomas and malignant carcinomas
• Benign adenomas are masses of the perianal glands that are not classified as cancerous and do not spread

Malignant carcinomas, or adenocarcinomas, are also masses of the perianal glands. These are uncommon cancerous masses that are hard to distinguish from benign adenomas, but can spread to other locations in the body and cause hypercalcemia, or increased blood calcium levels that can lead to kidney failure. Malignant carcinomas require more intensive diagnostic testing and treatments, therefore it is necessary to determine if your dog’s tumors are malignant.

While the definitive cause of perianal gland tumors is still unknown, testosterone is believed to influence cell proliferation in the glands. Male dogs have an increased risk compared to females in developing these tumors. For females, adrenocortical hormones may play an important role in tumor growth. 

Additionally, genetic factors may also influence the possible progression of this type of tumor. Breeds who seem to be at a higher risk include:

• Beagles
• Cocker Spaniels
• English Bulldogs
• Samoyed breeds 

A physical exam can help your veterinarian determine if the masses or nodules on your dog’s anal area may be tumors. Often a urinalysis is performed, as well as blood work that can reveal an elevated blood calcium level, a sign of these types of growths. 

Many perianal gland tumors will be benign, but a small percentage of these growths can be malignant. A tissue sample by a fine-needle aspirate or by a surgical biopsy will be examined under the microscope to determine what kind of tumor your dog has. Chest and abdominal X-rays and ultrasounds can also help to determine of the tumors have spread, such as to the lymph nodes or prostate gland.

Treatment for these tumors can vary, and can be more difficult if they have spread. Treatment for tumors that are diagnosed as malignant aims to improve your dog’s quality of life, while benign masses can be completely resolved. 

For intact, male dogs, the primary treatment is the removal of one or both testes. This eliminates much of the testosterone, which can result in regression of small and benign tumors. Your dog is monitored after castration to assess if further removal is necessary. 

In both male and female dogs, small tumors can also be removed with cryotherapy, which freezes off the masses. For larger or malignant tumors, surgical removal may be necessary. Fecal incontinence can result from surgery due to damage to the sphincter muscle which is next to the perianal gland. 

Chemotherapy and radiation therapy may also be prescribed in addition to castration, and are generally given over several weeks. Estrogen therapy can be administered to shrink tumors, and is used especially in cases where castration is not an option in male dogs. A side effect of estrogen therapy is a life threatening condition of bone marrow suppression.

Supportive treatments can include soothing creams for irritated anal skin, and medications to reduce blood calcium levels, improve kidney function, and alleviate pain and nausea.

For benign perianal gland tumors, recovery is very good. Neutering leads to a complete regression in 95% of these cases. Your dog may need post-operative care, and should be seen by your veterinarian in 1 to 3 months to monitor tumor regression. In a small percentage of cases, tumors may recur, but can be treated. 

If your dog has a malignant tumor, post-operative care may be longer and more intense. You may need to monitor your dog for complications, such as infections and fecal incontinence. Your dog may need frequent veterinary visits for treatments. Recovery is poor, as many dogs can die from the effects of the tumors within a year from diagnosis, or are euthanized.