Perianal Adenomas in Dogs: Hormone-Linked Tumors and Treatment Options

By Emiel Maddens · Reviewed in consultation with licensed veterinary professionals · Updated August 2026 · 9 min read

What Is a Perianal Adenoma in Dogs?

A perianal adenoma is a benign tumor arising from the hepatoid glands, the modified sebaceous glands packed into the skin surrounding a dog's anus, and its growth is directly driven by circulating testosterone. These glands are also called circumanal or perianal glands, and although they are concentrated in a ring around the anal opening, hepatoid tissue is scattered more widely than most owners realise. It appears along the tail base, over the prepuce, across the perineum, on the dorsal and ventral midline of the trunk and occasionally on the hind limbs, which is why a hormone-linked tumor can appear several centimetres away from the anus itself.

These glands are not true secretory glands in the way sweat or oil glands are. They have no duct and do not empty onto the skin surface, which means their function is still debated, with most evidence pointing toward the production of pheromone-like scent compounds. What matters clinically is that hepatoid cells carry androgen receptors, so testosterone acts as a continuous growth signal across a dog's lifetime.

Perianal gland tumors are among the most frequently diagnosed neoplasms in the intact male dog, historically ranking in the top three skin tumors in that population. Studies of canine perineal masses have consistently found that approximately 80 percent are benign adenomas, with adenocarcinomas and the less common epithelioma making up the remainder (Hayes & Wilson, 1977; Berrocal et al., 1989). The typical patient is an intact male dog over 8 years old, and the risk in intact males has been estimated at several times that of neutered males of the same age.

Perianal adenomas must not be confused with anal sac apocrine gland adenocarcinoma, an entirely different and malignant tumor of the anal sacs that frequently causes hypercalcaemia. The two conditions occupy nearly the same anatomical region but have opposite prognoses, which is exactly why no perianal mass should be assumed benign on appearance alone.

What Causes Perianal Adenomas to Develop?

Perianal adenomas develop because hepatoid gland cells express androgen receptors and respond to testosterone as a proliferative stimulus, so decades of continuous hormonal exposure in an intact male eventually drives a population of those cells into unregulated growth. This androgen dependence is the single most useful fact in the whole disease, because it explains both the epidemiology and the treatment.

Classic endocrine work established that these tumors are hormone-dependent neoplasms, that they occur overwhelmingly in intact males, and that removing the androgen source often causes established masses to shrink (Hayes & Wilson, 1977). The same research noted that oestrogens appear to have a protective or inhibitory effect on hepatoid tissue, which fits the observation that these tumors are rare in intact females and, when they do appear in a spayed female, should raise suspicion of an adrenal or ovarian remnant androgen source.

Other contributing factors include:

Age. Incidence climbs steeply after 8 years, with most cases diagnosed between 8 and 12 years, reflecting cumulative hormone exposure and age-related decline in cellular repair.

Breed predisposition. Cocker Spaniels, Beagles, Siberian Huskies, Samoyeds, Pekingese, Shih Tzus and Lhasa Apsos are reported at elevated risk, suggesting a heritable component to receptor density or gland volume.

Concurrent testicular tumors. Interstitial (Leydig) cell tumors produce excess androgens and can accelerate hepatoid gland proliferation, so a perianal mass in an intact male warrants a careful testicular examination.

Hyperadrenocorticism. Adrenal disease that raises sex steroid production can occasionally drive hepatoid growth even in a neutered dog, which is one of several reasons endocrine skin disease and tumor biology overlap so heavily in older dogs.

How Do Veterinarians Diagnose a Perianal Mass?

Veterinarians diagnose perianal masses with a combination of physical and rectal examination, fine needle aspirate cytology and, when malignancy is suspected or cytology is inconclusive, an incisional or excisional biopsy for histopathology. Cytology alone cannot reliably separate a benign adenoma from a well-differentiated adenocarcinoma, because both are composed of polygonal cells with abundant eosinophilic cytoplasm and round nuclei that resemble hepatocytes, which is where the name hepatoid originates.

A complete workup typically includes a digital rectal examination to assess the anal sacs and sublumbar lymph nodes, since anal sac adenocarcinoma is the key differential and often reveals itself as a firm mass at the four or eight o'clock position rather than in the perianal skin. Serum ionised calcium is measured in any suspicious case, because hypercalcaemia of malignancy is reported in a substantial proportion of anal sac adenocarcinomas and essentially never accompanies a simple adenoma. Abdominal imaging is added when the mass is fixed, ulcerated, rapidly growing or when regional lymph nodes feel enlarged.

Signs and Symptoms to Watch For

The earliest sign of a perianal adenoma is usually a small, firm, hairless nodule near the anus that an owner discovers by accident while grooming or after noticing the dog scooting. These masses commonly start at 0.5 to 2 centimetres and enlarge slowly over months. Many dogs have several at once, and multiple nodules in a ring pattern around the anus is a classic presentation rather than a sign of aggressive disease.

Because the tumors are covered by thin, hairless skin in a region subject to constant friction, moisture and faecal contamination, they ulcerate readily once they exceed roughly a centimetre. An ulcerated adenoma bleeds intermittently, leaving spots on bedding, and the dog responds by licking, which perpetuates the erosion.

Signs that warrant a veterinary appointment include:

Persistent scooting or dragging the rear along the floor
Excessive licking or chewing at the anus and tail base
A visible pink, red or ulcerated nodule near the anal opening
Blood or serous discharge on bedding or after defecation
Straining to defecate, or producing ribbon-shaped stools
Malodour that persists despite bathing
Swelling that extends toward the tail base or perineum

Straining to defecate deserves emphasis. A large perianal mass can physically narrow the anal canal, and in intact males this sign can also reflect perineal hernia, a condition that shares the same androgen-linked risk profile and frequently occurs in the same patients. Any older intact male with tenesmus needs a rectal examination rather than a course of stool softeners.

Distinguishing an adenoma from other tail base lesions matters, and our guide to dog tail skin problems covers the overlapping picture of stud tail, folliculitis and localised hair loss in this region.

Treatment Options for Perianal Adenomas

Treatment for a perianal adenoma is castration combined with surgical excision, and this pairing is curative in the large majority of cases. Castration removes the testosterone that drives proliferation, and published series report that a meaningful proportion of adenomas shrink substantially or resolve on castration alone, while recurrence after combined castration and excision is generally reported below 10 percent (Turek & Withrow, 2013). Excision without castration in an intact male is the one approach to avoid, because the hormonal stimulus remains and new nodules commonly appear at other hepatoid sites.

Small nodules may be managed with cryosurgery or electrosurgical excision under sedation, and our overview of cryotherapy for dog skin growths explains when freezing is appropriate for small cutaneous lesions and when it is not. Surgeons approach perianal excision cautiously because the external anal sphincter runs immediately beneath these masses, and aggressive resection risks faecal incontinence. For dogs that are poor anaesthetic candidates, chemical castration with a deslorelin implant has been used to achieve androgen suppression, though the effect is temporary and surgical castration remains the standard.

Wound care in this location is genuinely difficult. A perianal surgical site or an ulcerated mass awaiting surgery sits directly in the path of faecal flora, and secondary bacterial colonisation with Staphylococcus pseudintermedius is a routine complication that delays healing and increases discomfort. This is where antiseptic hygiene has a defined supportive role. Chlorhexidine Spray contains 2% chlorhexidine gluconate, a cationic biguanide that binds to the negatively charged bacterial cell wall, disrupts the cytoplasmic membrane and causes precipitation of intracellular contents. Chlorhexidine also has substantivity, meaning it binds to the stratum corneum and continues to exert antibacterial activity for hours after application, which is valuable on skin that is repeatedly re-contaminated. It is a supportive hygiene measure around the lesion, not a treatment for the tumor itself, and it should only be used on surgical sites with your veterinarian's direction.

Post-operative care follows the same principles as any perineal procedure, and our article on dog skin after spay or neuter recovery sets out what normal healing looks like and which changes signal a problem. For broader context on antiseptic use in canine skin care, see chlorhexidine for dogs.

Prevention and Long-Term Management

The most effective prevention for perianal adenomas is castration before the tumors have decades of androgen exposure to build on, since the disease is functionally absent in dogs neutered young. This is not an argument for early neutering in every dog, because timing of castration interacts with orthopaedic development, certain other cancers and behaviour in ways that vary considerably by breed and size. It is a factor to weigh with your veterinarian rather than a standalone directive.

For dogs that remain intact, structured monitoring is the practical alternative. A monthly hands-on check of the perianal region takes under a minute: lift the tail in good light, look for nodules, asymmetry or ulceration, and note the size of anything you find. Owners who record measurements catch growth trends that a once-yearly examination misses entirely.

Long-term management after successful surgery centres on three habits:

Recheck examinations. Because hepatoid tissue is distributed well beyond the anus, new nodules can appear at the tail base or prepuce. A rectal and perianal examination at every annual or biannual visit is appropriate for any dog with a history of these tumors.

Weight and stool quality. Obesity and chronic soft stool both increase perineal soiling and friction, which worsens ulceration risk on any mass and slows healing on any surgical site.

Perineal hygiene. Long-coated breeds benefit from a trimmed sanitary area, and gentle cleaning after defecation reduces the bacterial load on compromised skin. Avoid alcohol-based or fragranced wipes on ulcerated tissue, which increases irritation.

Finally, keep the differential list open. Older dogs with endocrine disease develop several distinct skin problems at once, and conditions such as tail gland hyperplasia can coexist with hepatoid tumors in the same patient, since both involve androgen-responsive sebaceous tissue. Any new lump in this region deserves an aspirate rather than an assumption.

Frequently Asked Questions

Will neutering make my dog's perianal adenoma go away?

Often, yes. Perianal adenomas are androgen-dependent, and castration removes the testosterone driving their growth. A substantial proportion of adenomas shrink significantly or resolve after castration alone, and when castration is combined with surgical excision, reported recurrence rates fall below 10 percent. Excision without castration in an intact male is far more likely to be followed by new nodules at other hepatoid gland sites.

Are perianal adenomas in dogs cancerous?

Perianal adenomas are benign tumors. They do not metastasise, and they cause problems locally through ulceration, bleeding and pressure rather than through spread. However, roughly 20 percent of perianal gland tumors are adenocarcinomas, which are malignant, and a separate tumor of the anal sacs, apocrine gland adenocarcinoma, is aggressive and often causes high blood calcium. Only cytology or biopsy can separate them reliably.

Can female dogs get perianal adenomas?

They can, but it is uncommon because oestrogen appears to inhibit hepatoid gland proliferation. A perianal adenoma in a spayed female is unusual enough that it should prompt investigation for an androgen source, such as an ovarian remnant or an adrenal tumor producing sex steroids. In intact females the tumors remain rare compared with intact males of the same age.

How much does perianal adenoma surgery cost, and what is recovery like?

Costs vary widely by region and by whether castration is performed at the same time, so your veterinarian is the right source for a figure. Recovery typically takes 10 to 14 days. The main challenges are keeping the site clean in a heavily contaminated region, preventing licking with an e-collar, and maintaining soft stool so defecation does not stress the incision. Faecal incontinence is a recognised but uncommon risk when large masses require extensive resection near the anal sphincter.

What can I put on an ulcerated perianal mass at home?

Nothing should go on an ulcerated perianal mass without a veterinary diagnosis first, because home care on an undiagnosed malignant tumor delays the treatment that matters. Once your veterinarian has confirmed the diagnosis and directed care, gentle antiseptic hygiene with a 2% chlorhexidine gluconate product is a common supportive measure to reduce bacterial contamination of the eroded skin. Avoid alcohol-based, fragranced or hydrogen peroxide products, which damage healing tissue.

Sources

1. Hayes HM, Wilson GP. Hormone-dependent neoplasms of the canine perianal gland. Cancer Research. 1977;37(7):2068-2071.
2. Berrocal A, Vos JH, van den Ingh TS, et al. Canine perineal tumours. Zentralblatt fur Veterinarmedizin Reihe A. 1989;36(10):739-749.
3. Turek MM, Withrow SJ. Perianal tumors. In: Withrow and MacEwen's Small Animal Clinical Oncology. 5th ed. Elsevier; 2013:423-431.
4. Vail DM, Withrow SJ, Schwarz PD, et al. Perianal adenocarcinoma in the canine male: a retrospective study of 41 cases. Journal of the American Animal Hospital Association. 1990;26:329-334.
5. Petrov EA, Miller MA, et al. Histologic classification and immunohistochemistry of canine hepatoid gland tumors. Veterinary Pathology. 2019;56(3):380-388.

Related Reading

• Dog Tail Skin Problems: Stud Tail, Hair Loss, and Infections
• Cryotherapy for Dog Skin Growths: How Freezing Removes Lesions Safely
• Dog Skin After Spay or Neuter: Normal Recovery
• Stud Tail in Dogs: Tail Gland Hyperplasia Guide

Emiel Maddens

Founder of Vetified. Develops topical antifungal and antimicrobial formulations for companion animals. Vetified products are listed on DailyMed and manufactured through FDA-registered facilities in the United States.

Veterinary review: All Vetified content is developed in consultation with licensed veterinary professionals and references peer-reviewed research published in journals including Veterinary Dermatology, JAVMA, and Journal of Small Animal Practice.