Perianal gland tumors start in small oil glands in the skin around a dog’s anus. These glands are a modified kind of sebaceous (oil) gland. Under the microscope their cells look a little like liver cells, so they are also called hepatoid glands, and the tumors are also called hepatoid gland tumors [4].
Most of these tumors are benign (not cancer). The malignant type is much less common [2][3]. Only a lab check of tissue from the lump can tell them apart.
See your vet about any lump near your dog’s anus or under the tail, and about any lump there that bleeds.
For anal sac (anal gland) problems and scooting, see dog anal gland problems.
Where they grow
The glands sit mainly in the skin around the anus, so that is where most of these tumors appear. The same kind of gland is also found at the base of the tail, along the back, on the sheath of the penis, in the groin and on the inner thighs, so a tumor can show up in those places too [1][4].
Which dogs get them
- Male dogs that are not neutered: researchers describe these tumors mostly in intact males. Male hormones drive the growth of these glands, and the tumor cells carry receptors for sex hormones [2][4]. They are among the more common tumors seen in male dogs [1].
- Females: the tumors are rare in females. When they do occur, it is mostly in spayed females [4].
- Age: most affected dogs are older [1][4].
- Breeds: studies include both mixed-breed and purebred dogs, so any dog can be affected [1][2].
Signs
You may notice one or more lumps around the anus or under the tail. Some lumps grow large, and a lump in this area can form an open sore and bleed. A large lump near the anus may also make it harder for your dog to pass stool. Any of these is a reason to see your vet.
Benign and malignant types
Benign perianal gland tumors. Adenomas are the most common type. They are made of orderly, well-formed gland cells and behave in a benign way [2][5].
Perianal gland adenocarcinomas. These are the malignant type and are uncommon. Their cells look disorganized under the microscope [2]. When they spread, they most often go to the lymph nodes inside the belly near the lower back, and less often to organs such as the lungs [2].
How vets diagnose them
Your vet will look at and feel the lump, and may take cells or a small piece of tissue for a lab to examine [2][3]. A tissue check under the microscope (histopathology) is what tells a benign tumor from a malignant one [2]. For a malignant tumor, your vet may also check the nearby lymph nodes for spread [2]. Your vet will explain which tests your dog needs.
Treatment
Your vet will advise on treatment. In published reports it depends on the type of tumor:
- Benign tumors in male dogs: researchers report that neutering together with removal of the lump works well, and the tumor rarely comes back [2]. Because these tumors respond to male hormones, neutering is part of the plan for many intact males [2][4].
- Malignant tumors: neutering and hormone treatment have not been shown to work for these. Good results have come from removing the tumor with a wide margin of healthy tissue around it [1][3].
- Surgery near the anus: the surgeon plans the margin with care, because the muscle that closes the anus has to keep working [3].
At home, as directed by a vet:
- keep the area under the tail clean in the way your vet shows you;
- tell your vet if your dog strains to pass stool, or if a lump grows, opens or bleeds;
- go back for every recheck.
Outlook
Outcomes vary between types:
- Benign tumors: researchers describe the outlook as favorable after treatment [2].
- Malignant tumors: the outlook depends on how large the tumor is and whether it has spread when it is found. Small tumors that have not spread do better [2].
These are statements about groups of dogs. They cannot predict how one dog will do. Your vet can explain what this means for your dog.
When to see your vet
See your vet if your dog has:
- one or more lumps around the anus;
- a lump on the tail, along the belly, or on the back near the tail;
- a lump that has an open sore or bleeds;
- trouble passing stool.
FAQ
Is a lump near my dog’s anus always cancer?
No. Most perianal gland tumors are benign adenomas, and the malignant type is uncommon [2][3]. Your vet needs a sample to know which it is.
Does neutering help?
For the benign tumors in male dogs, researchers report good results from neutering together with removal of the lump [2]. It has not been shown to help with the malignant type [1]. Your vet will advise.
Are these the same as anal gland problems?
No. Anal sac tumors grow in the same area and can look similar at first, but they are a different tumor that tends to behave much more aggressively [5]. Only a lab check tells them apart. For anal sac problems, see dog anal gland problems.
The bottom line
Perianal gland tumors grow from oil glands around a dog’s anus, and sometimes on the tail, back, groin or thighs. They are seen mostly in older male dogs that are not neutered. Most are benign. The malignant type is uncommon, can spread to lymph nodes, and is treated by removing it with a wide margin. A lab check of the tissue tells which type it is, and your vet will advise on treatment.
This article is for general information only and does not replace advice from your veterinarian. If your dog has a lump near the anus or trouble passing stool, see your vet.
Sources
- Brodzki A, Łopuszyński W, Brodzki P, et al. Pharmacological Treatment of Perianal Gland Tumors in Male Dogs. Animals (Basel). 2023;13(3):463. doi:10.3390/ani13030463 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC9913509/
- Maniscalco L, Olimpo M, Parisi L, et al. A novel scoring system proposal to guide treatment of dogs with hepatoid gland tumors. Frontiers in Veterinary Science. 2025;12:1451510. doi:10.3389/fvets.2025.1451510 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC11841504/
- Zanuto EBM, Melo SR, Januário EV, et al. Diagnostic Value and Application of Infrared Thermography in the Analysis of Circumanal Gland Tumors. Frontiers in Veterinary Science. 2021;8:692221. doi:10.3389/fvets.2021.692221 (CC BY). https://pmc.ncbi.nlm.nih.gov/articles/PMC8354560/
- Brodzki A, Łopuszyński W, Millan Y, et al. Androgen and Estrogen Receptor Expression in Different Types of Perianal Gland Tumors in Male Dogs. Animals (Basel). 2021;11(3):875. doi:10.3390/ani11030875 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC8003237/
- Haake AFH, Loriani Fard AK, Jovanovic VM, et al. Extremes on the benign-malignant tumour spectrum: Distinct transcriptomic landscapes between two common canine perianal neoplasms based on the hallmarks of cancer. PLOS One. 2026;21(6). doi:10.1371/journal.pone.0351773 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC13286202/