Benign Tumor of the Glands on the Anus in Dogs (Perianal Adenoma)

  • Occurrence: common
  • Location of disease: Abdomen/pelvis
Author: Dr. med. vet. Gisa Löwe | Last modified: 09.08.2026
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When to visit the vet?

Non-urgent see a veterinarian within 2–3 days

?

If the condition worsens / symptoms persist, consult a veterinarian.

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Definition

A perianal adenoma is a benign growth in the area of the anus or the surrounding skin in dogs. These tumors are common in older, unneutered male dogs and are related to the hormone testosterone.

BASICS/CAUSES:

Perianal adenomas develop from the sebaceous glands present in the skin around the anus. These glands are targeted by sex hormones, especially testosterone, and can grow excessively when these hormones are present in higher concentrations.

The hormonal dependence of these tumors explains why they occur more frequently in males than in females. These tumors are rare in neutered males and females, which highlights the importance of testosterone.

Genetic predisposition can also play a role, as certain dog breeds like Cocker Spaniels, Beagles, and Bulldogs have a higher predisposition for developing these tumors. This genetic component is an important consideration when it comes to breeding and selecting breeding animals.

The most important facts at a glance

Perianal adenomas in dogs are benign Tumors near the anus that develop under the influence of sex hormones, especially testosterone. They usually appear as flesh-colored, hairless Swelling in the Anal region swelling and can cause Itching or Inflammatory conditions. Rarer symptoms include blood in the stool or Weight loss. Diagnosis is made through a clinical examination in which the veterinarian palpates the affected area and, if necessary, takes tissue samples for microscopic examination to determine the type of tumor. Blood tests and ultrasound can also help with clarification. The primary treatment method is surgical tumor resection. For unneutered males, castration / neutering is often recommended to lower testosterone levels and minimize the risk of recurrence / relapse. For dogs that cannot undergo surgery, drug treatments should be considered. The prognosis is generally good, especially with early detection and treatment. Castration / neutering can significantly reduce the likelihood of recurrence. For prevention, castration / neutering of male dogs is recommended, especially if they are not intended for breeding. Regular check-ups and care of the Anal region swelling help detect changes early. Breeders should consider genetic predispositions to reduce risk in future generations.

Causes

  • Influence of sex hormones, especially testosterone

Symptoms

Rare symptoms:

The most common symptoms of a perianal adenoma are visible lumps or masses around the dog’s anus. These lumps are usually round, smooth, and can vary in size from a pea to a golf ball. They are often well-defined and feel firm.

Other signs may include Itching or irritation in the anus area, causing the dog to lick frequently or rub along the ground. In some cases, the Tumors may ulcerate or bleed, which puts additional strain on the dog and carries a risk of infection.

Difficulty passing stool or changes in bowel movements may also occur, especially if the tumor is large and affects the anus or rectum. This can lead to constipation or Pain when defecating.

Therapy

The primary treatment for perianal adenomas is usually surgical. Removing the tumor is the most effective method to relieve symptoms and prevent it from growing further or ulcerating.

For unneutered males, castration / neutering is often recommended, as removing the testicles lowers testosterone levels, which reduces the risk of the tumor recurring. This is especially important because the tumors are hormone-dependent.

In cases where the tumor cannot be surgically removed or the dog is not a candidate for surgery, drug treatments can be considered. Anti-androgen medications or hormone therapies can help slow tumor growth.

Prognosis and follow-up care

The prognosis for dogs with perianal adenomas is generally good, especially if the tumor is detected and treated early. Surgical removal often leads to a complete cure.

After castration / neutering, the likelihood of the tumors recurring is significantly reduced. Even if the tumor cannot be completely removed, drug treatment can often control tumor growth and improve the dog’s quality of life.

In rare cases, a perianal adenoma can become malignant, so regular monitoring is important. Dogs that have been affected should be examined regularly by a veterinarian to detect any recurrence early.

Prevention

The most effective prevention measure against perianal adenomas is castration / neutering of male dogs, especially if they are not intended for breeding. This lowers testosterone levels and significantly reduces the risk of tumor development.

Regular examination and care of the anus and surrounding skin can help detect changes early. If a lump or Swelling is suspected, the dog should be taken to a veterinarian immediately.

For breeders, it is important to consider the genetic predisposition of dogs. Selecting breeding animals without a family history of perianal adenomas can help reduce the risk for future generations.

Outlook on current research

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In veterinary medicine, perianal adenoma is usually a benign tumor of the hepatoid (circumanal) glands around the anus. It occurs particularly often in older, unneutered male dogs and is considered hormone-dependent, especially androgen-dependent. That is precisely why the most important clinical advance was the realization that many of these Tumors can shrink or regress after castration / neutering. (merckvetmanual.com, vcahospitals.com)

Current research prospects mainly focus on three areas. First, it is about more precise differentiation between adenoma and adenocarcinoma, i.e., between benign and malignant tumor. Histopathological, immunohistochemistry, and potential prognosis markers are playing an increasingly important role here. Second, there is interest in why such Tumors can also occur in neutered males or females, even though classic androgen dependence does not fully explain it then. (merckvetmanual.com, pubmed.ncbi.nlm.nih.gov)

The third focus concerns therapy planning. In the future, it will become more important which Tumors can be influenced hormonally alone, when surgical removal makes sense, and how recurrences can be predicted better. Overall, the outlook is good: Research is moving toward biologically more precise classification and individually tailored, often less invasive treatment.

Frequently Asked Questions (FAQs)

1. What is a perianal adenoma?
A perianal adenoma is a benign tumor that originates from the perianal glands, i.e., the modified sebaceous glands around the anus. These glands are hormone-dependent, especially on testosterone. Perianal adenomas therefore occur predominantly in older, unneutered male dogs.
2. Which dogs are particularly affected?
Almost exclusively unneutered male dogs from the age of seven are affected. Predisposed breeds include Cocker Spaniel, Siberian Husky, Malamute, Beagle, and Samoyed. In females, perianal adenomas are very rare and usually occur in connection with estrogen-producing ovarian tumors.
3. What symptoms does a dog show?
Typical signs are one or more nodular masses around the anus, sometimes at the base of the tail, on the perineum, or on the prepuce. The Tumors can ulcerate and bleed; they often cause Itching, Licking at the site, occasional problems passing stool, or tenesmus. Pain is usually only present with superficial inflammation.
4. How is the diagnosis made?
Clinically, the location is typical. Fine-needle aspiration provides clues, but the definitive diagnosis is made by histology after an excisional biopsy. Particularly important is differentiation from malignant perianal gland adenocarcinoma and apocrine anal sac adenocarcinoma, which can look clinically similar.
5. How are perianal adenomas treated?
Therapy consists of surgical removal and simultaneous castration / neutering. Castration / neutering removes the hormonal basis from these androgen-sensitive Tumors, so they usually do not become recurrent after surgery. In neutered males with newly appearing nodules, a malignant variant must be considered in particular.
6. Can castration / neutering alone cause the tumor to regress?
Yes, many small perianal adenomas regress significantly or disappear completely after castration / neutering alone. However, for large, ulcerated, or problematic Tumors, additional surgical removal is useful to achieve rapid relief of symptoms.
7. How high is the recurrence / relapse rate?
After castration / neutering and complete surgical removal, the recurrence / relapse rate is low. Without castration / neutering, it is up to 50%, because untreated, additional adenomas develop in other locations. Regular monitoring of the anogenital area is advisable.
8. How does an adenoma differ from an adenocarcinoma?
Perianal adenocarcinoma is rare, but it grows invasively, metastasizes to regional lymph nodes, and does not respond to castration / neutering. Clinically, the two often differ very little; histology is decisive. Any growing or ulcerating mass on the perineum must be taken seriously and biopsied.
9. What is the difference from apocrine anal sac adenocarcinoma?
Apocrine anal sac adenocarcinoma originates from the paired anal sac glands, not from the superficial perianal glands. It is highly malignant, metastasizes early, often leads to hypercalcemia, and must be treated aggressively. Clinically, it is characterized by a palpable mass lateral to the anus (at 4 or 8 o’clock).
10. What is the prognosis?
The prognosis for classic perianal adenoma is excellent. After surgery and castration / neutering, dogs usually continue to live symptom-free. Regular monitoring of the Anal region swelling is important, especially in male dogs with previously confirmed adenomas.

Literature

  • Maniscalco, L., Olimpo, M., Parisi, L., Buracco, P., Mazzone, E., Martinelli, G., Martano, M., Iussich, S., & Morello, E. (2025). A novel scoring system proposal to guide treatment of dogs with hepatoid gland tumors. Frontiers in Veterinary Science, 12, Article 1451510. https://doi.org/10.3389/fvets.2025.1451510
  • Brodzki, A., Łopuszyński, W., Brodzki, P., Głodkowska, K., Knap, B., & Gawin, P. (2023). Pharmacological treatment of perianal gland tumors in male dogs. Animals, 13(3), Article 463. https://doi.org/10.3390/ani13030463
  • Brodzki, A., Łopuszyński, W., Millan, Y., Tatara, M. R., Brodzki, P., Kulpa, K., & Minakow, N. (2021). Androgen and estrogen receptor expression in different types of perianal gland tumors in male dogs. Animals, 11(3), Article 875. https://doi.org/10.3390/ani11030875
  • Sobczyńska-Rak, A., Żylińska, B., Jarosz, Ł., Brodzki, A., & Tatara, M. R. (2018). EGF level in hepatoid gland adenomas and hepatoid gland epitheliomas in dogs after administering tamoxifen. In Vivo, 32(5), 1175–1181. https://doi.org/10.21873/invivo.11361
  • Evans, S. J. M., Connolly, S. L., Schaffer, P. A., Vieson, M. D., Stiles, A., & Moore, A. R. (2018). Basal cell enumeration does not predict malignancy in canine perianal gland tumor cytology. Veterinary Clinical Pathology, 47(4), 634–637. https://doi.org/10.1111/vcp.12671
  • Sabattini, S., Renzi, A., Rigillo, A., Scarpa, F., Capitani, O., Tinto, D., Brenda, A., & Bettini, G. (2019). Cytological differentiation between benign and malignant perianal gland proliferative lesions in dogs: A preliminary study. Journal of Small Animal Practice, 60(10), 616–622. https://doi.org/10.1111/jsap.13062
  • Chantawong, P., Mamom, T., Tangtrongsup, S., Chitsanoor, S., & Boonsriroj, H. (2022). First study on the immunohistochemical expression of cyclooxygenase-2 and clinicopathological association in canine hepatoid gland neoplasms. Veterinary World, 15(10), 2432–2441. https://doi.org/10.14202/vetworld.2022.2432-2441
  • Pisani, G., Millanta, F., Lorenzi, D., Vannozzi, I., & Poli, A. (2006). Androgen receptor expression in normal, hyperplastic and neoplastic hepatoid glands in the dog. Research in Veterinary Science, 81(2), 231–236. https://doi.org/10.1016/j.rvsc.2005.11.001