Most dog parents would prefer to avoid their dog’s perianal area. It’s more fun to focus on the end with the puppy dog eyes and the slobbery smile, but ignoring the rear end can mean that you can miss important issues, like a lump near your dog’s bottom called a perianal tumor.
While most are adenomas, which are benign, it’s important to have any new lump checked by your veterinarian. Understanding what these tumors are, how they’re diagnosed, and when they need treatment can help you make the best decision for your dog.
What is a Perianal Adenoma in Dogs?
Perianal adenomas are tumors that grow in the hepatoid glands around a dog’s bottom. Hepatoid glands are small skin glands that help produce natural oils and scents. They’re found around the anus, at the base of the tail, and in the groin.
According to a study published in Frontiers in Veterinary Science, perianal adenomas account for 25% of all skin tumors in dogs, so they’re quite common.
Types of Perianal Tumors in Dogs
While adenomas are the most common type, perianal tumors is a broad category that includes both benign (non-cancerous) and malignant (cancerous) tumors.
Benign Adenomas
Fortunately, the vast majority of perianal tumors happen to be non-cancerous. Those include:
Perianal adenomas
Anal gland adenomas (apocrine gland adenoma): a type of tumor that arises from the anal glands rather than the hepatoid glands
Malignant Carcinomas/Adenocarcinomas
Cancerous tumors can also show up in the perianal area, though far less common than their benign counterparts. They include:
Anal sac adenocarcinomas (apocrine gland adenocarcinoma)
Hepatoid (perianal) adenocarcinoma
Malignant and benign tumors look very similar to each other but behave very differently. It’s important to seek veterinary care if you notice any kind of lump or bump in your dog’s perianal area, just to be safe.
Causes of Perianal Adenoma in Dogs
The cause of perianal, and any other tumor for that matter, is complex and intertwined. We often can’t pinpoint an exact cause, but we do know that perianal adenomas seem to have a hormonal component.
They are five to six times more common in intact males than in neutered males, suggesting that testosterone plays a strong role. Interestingly, intact females are less likely than spayed females to develop the tumor, meaning that estrogen likely plays a role in inhibiting them.
Affected dogs often have testicular tumors as well.
Symptoms and Identification of Perianal Tumors in Dogs
Dogs with perianal adenomas often show up with:
A small lump or bump near your dog’s bottom that may be pink, flesh-colored, or hairless. Although they’re most often found around the anus, these tumors can also develop under the tail or on the skin near the genitals.
Bumps may ulcerate and bleed
Licking of genital area
Benign and malignant tumors look alike, but malignant types tend to grow rapidly and invade local tissues
Affected Breeds of Canine Perianal Gland Tumors
While any dog can develop a perianal adenoma, some breeds appear to be at higher risk, including Cocker Spaniels and German Shepherds. Older studies have also suggested an increased risk in Arctic breeds, such as Siberian Huskies and Samoyeds. Researchers don’t yet know exactly why these breeds are predisposed, but they have several theories:
Inherited hormone sensitivity. Perianal adenomas are strongly influenced by male hormones (androgens). Researchers suspect some breeds may have hepatoid glands that are naturally more sensitive to these hormones, making abnormal cell growth more likely over time. This idea is supported by studies showing these tumors contain abundant androgen receptors, although breed-specific differences haven’t yet been proven.
Differences in hormone regulation. Another theory is that certain breeds may regulate or respond to sex hormones differently as they age. Researchers have suggested that subtle differences in steroid hormone pathways could influence tumor development.
Differences in tumor behavior. Some evidence suggests breed may influence not only whether a tumor develops but also how it behaves. For example, German Shepherds and some Arctic breeds may have a higher risk of tumors progressing to carcinoma, while Cocker Spaniels commonly develop benign adenomas that are less likely to become cancerous.
How Vets Diagnose Perianal Adenomas in Dogs
Any lump or bump on your dog should be properly diagnosed by a veterinarian. Looks alone can’t determine if a tumor is benign or malignant. Veterinarians need to get a sample of the tissue in order to determine the cellular makeup under a microscope.
Your vet will perform a thorough exam to look for any other tumors as well as checking your dog’s overall health, then they will collect a sample of the tumor through a fine-needle aspirate or biopsy and examine the sample under a microscope or send it to a pathology lab. Perianal adenomas can look similar to several types of lumps in dogs, including cysts and lipomas, so collecting a sample is necessary.
Blood work and imaging may also be necessary depending on their findings.
Treatment of Perianal Adenomas in Dogs
Perianal adenomas are typically treated with surgical removal. For intact males, this means removal of the tumor as well as neutering in order to remove the hormonal influence. Tumors that are located close to the anal sphincter or that have poorly defined borders may not be good candidates for removal. Instead, your vet may choose to see how much these tumors shrink following neutering and then continue to monitor them for further growth or ulceration.
Cryotherapy or radiation may also be options depending on the size and location of the tumor.
Recovery and Management of Perianal Adenomas in Dogs
Most dogs will recover quickly from a perianal adenoma removal surgery. They require:
Strict rest for 10-14 days
E-collar to prevent licking
Keeping the area clean, no bathing
Monitoring bowel movements and preventing constipation
Dogs will either be neutered prior to or at the same time as the tumor removal, so recovery times may vary.
Veterinary Cost of Treating Perianal Adenomas in Dogs
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 many dogs, neutering, surgical removal, and biopsy may cost anywhere from about $1,000 to $3,000, depending on your location and the complexity of the procedure. If referral surgery, radiation therapy, or oncology care is needed, total treatment costs can exceed $5,000 and may reach $10,000 or more.
Diagnosing and treating perianal adenomas can get pricey. Fortunately, a dog health insurance policy through Embrace Pet Insurance can help cover these unexpected costs, so you can focus on getting your pup’s rear end back to normal.
Adding optional coverage through a Wellness Rewards policy can help you budget for routine costs like wellness exams, which can help you catch issues like perianal adenomas while they’re still small.
Prevention of Perianal Adenomas in Dogs
Because perianal adenomas are fueled by male hormones, neutering is the most effective way to reduce the risk in male dogs. Regular veterinary exams and routine at-home checks of your dog’s skin, including around the tail and rear end, can also help you catch new lumps early, when they’re often easier to treat.
Most of us would rather admire our dog’s wagging tail than inspect what’s underneath it, but taking a quick look every now and then is worth the effort. While discovering a lump can be alarming, most perianal adenomas are benign and highly treatable. With your veterinarian’s help, most dogs recover quickly and get back to enjoying life.