Ceruminous glands are the glands that make earwax in the ear canal. They are a special kind of sweat gland [1]. A ceruminous gland tumor is a growth that starts in these glands, most often in the outer ear canal [1]. These tumors can be benign (not cancer) or malignant (cancer) [1].
If one ear keeps having discharge or swelling and is not getting better with treatment, go back to your vet. Long-lasting ear inflammation that does not improve with treatment is one of the reasons vets look more closely at the ear canal, for example with a CT scan [2].
For ear infections in dogs, see ear infections in dogs. For ear problems in cats, see cat ear mites and ear problems.
Dogs and cats differ
Dogs. Ear canal tumors in dogs tend to behave less aggressively than in cats [2][4]. Many are benign, and the earwax gland adenoma is the most common benign ear canal tumor in dogs [1][2]. Its cancerous form, the earwax gland adenocarcinoma, is also seen in dogs [1]. In published case reports, affected dogs were mostly middle-aged or older, and the tumor was nearly always in one ear only [1]. Where the breed was recorded, Cocker Spaniels were the pure breed named most often, but the numbers were small [1].
Cats. Tumors of the ear canal are uncommon in cats, but most of them are malignant [3]. The earwax gland adenocarcinoma is one of the most common cancers of the cat ear canal [3]. Affected cats in published reports were mostly middle-aged or older [1]. Unlike in dogs, many cats had growths in both ears, mostly the benign kind [1].
What can lead to them
The exact cause is not known. Pets with a long history of ear inflammation, itching, ear discharge or repeated ear infections seem to be at higher risk [1]. Researchers think the cancerous form may develop after long-lasting inflammation in the ear canal [2].
Spaniel breeds also tend to have more earwax glands in their ear canals than some other dogs [4].
Signs
The signs often look like a stubborn ear infection. A tumor can block the canal, so wax and debris build up and infection is common alongside it [2]. Watch for:
- discharge from one ear, or wax and debris that keep coming back [1][2];
- itching, head shaking or rubbing at the ear [1][4];
- a lump or swelling you can see in the ear canal [2];
- hearing loss [4][5].
If the problem reaches the middle ear, a pet may hold its head to one side, show pain when opening the mouth or chewing, or have reduced hearing [5]. If the inner ear is involved, a head tilt, loss of balance and flicking eye movements can appear [5]. Some pets get a drooping eyelid, ear or lip on one side because nearby nerves are affected [5].
Look-alikes
Other growths can sit in the same place. In dogs, these include papillomas (wart-like growths), oil gland tumors, basal cell tumors and squamous cell carcinoma [2][4]. In cats, inflammatory polyps are the most common growths in the outer ear canal that are not tumors, and squamous cell carcinoma is another common cancer of the ear [3].
Ongoing ear inflammation can also cause thickened, swollen tissue in the ear canal. In cats, one such condition is proliferative and necrotizing otitis externa.
How vets diagnose them
- A look inside the ear. A video otoscope is a small camera for looking inside the ear canal. Vets can also use it to take samples from a growth [1].
- Cell samples. A sample of cells looked at under a microscope can help tell a polyp from a tumor, but it cannot confirm the tumor type on its own [1].
- A biopsy. A piece of tissue checked in a lab (histopathology) is how these tumors are confirmed [1][2][3].
- CT scan. A CT scan shows how far the growth reaches, including into the middle ear and nearby bone, and helps plan surgery [2][3]. Benign and malignant growths can look alike on CT, so a biopsy is still needed [2][3].
Treatment
Your vet will advise on treatment. Surgery to remove the tumor is the main treatment [1]. The type of surgery depends on where the tumor sits and whether it is malignant; malignant tumors usually need larger surgery to remove all of the affected tissue [1]. Larger ear surgery can have complications, such as wound problems, hearing loss or nerve damage, so talk the options through with your vet [1]. Other options described for some pets include removing the growth with a laser through a video otoscope, and radiation therapy when a malignant tumor could not be fully removed [1].
At home, as directed by a vet:
- give ear treatments only as your vet shows you;
- note which ear is affected and any change in discharge, swelling, balance or hearing, so you can tell your vet;
- go back for every recheck.
Outlook
Outcomes vary between dogs and cats and between tumor types:
- After a benign tumor is fully removed, the outlook is generally good [1].
- A malignant tumor can come back in the same place or spread [1]. Spread usually stays in the nearby lymph nodes; spread to the salivary glands, lungs or other organs is rare [1].
- Ear canal tumors often do well when they are found early and treated promptly [1].
- Surgery may lengthen survival and give a good quality of life [1].
These are statements about groups of animals. They cannot predict how one pet will do. Your vet can explain what the lab results mean for your own dog or cat.
When to see your vet
See your vet if your dog or cat has:
- discharge from one ear, or wax and debris that keep coming back [1][2];
- head shaking, itching or rubbing at the ear [1][4];
- a lump or swelling in or near the ear canal [2];
- hearing loss [4][5];
- a head tilt or loss of balance [5];
- ear inflammation that does not get better with treatment [2].
FAQ
Are earwax gland tumors cancer?
They can be either [1]. In dogs, many ear canal tumors are benign; in cats, most ear canal tumors are malignant [2][3]. A biopsy tells which.
Why does my vet need a biopsy if there is already a scan?
Benign and malignant growths can look alike on a CT scan, so a tissue sample checked in a lab is needed to confirm what the growth is [2][3].
Is it just an ear infection?
An ear infection and a tumor can cause similar signs, and a tumor that blocks the canal often comes with an infection [2]. Long-term ear inflammation is also linked to these tumors [1]. If one ear does not get better with treatment, ask your vet about checking for a growth.
The bottom line
Ceruminous gland tumors grow from the earwax glands in the ear canal. In dogs, many ear canal tumors are benign, while in cats most are malignant. Signs include discharge, head shaking, itching and swelling, usually in one ear. A biopsy tells what the growth is, and your vet will advise on treatment. If one ear is not getting better with treatment, go back to your vet.
This article is for general information only and does not replace advice from your veterinarian. If your pet has a long-lasting problem in one ear, a head tilt or loss of balance, see your vet.
Sources
- Lavanya TR, Kumar P, Kok MK, Ong SM, Radzi R, Selvarajah GT. Ceruminous Gland Tumors in Canines and Felines: A Scoping Review. Animals. 2025;15(8):1138. CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC12024219/
- Veitch K, Gremillion C, Levine G, Coy C, Wisnoski M, Griffin JF, Waller K. Computed Tomographic Features of Benign and Malignant External Ear Canal Neoplasms in 39 Dogs. Veterinary Radiology & Ultrasound. 2026;67(1):e70128. CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC12788333/
- Wisnoski M, Gremillion C, Levine G, Coy C, Veitch K, Waller K, Griffin JF. Computed tomographic findings in 25 cats with ear canal neoplasia. Veterinary Radiology & Ultrasound. 2025;66(1):e13467. CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC11649876/
- Torres SMF, et al. 2.10 Otitis Externa: Dogs and Cats. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota Libraries Publishing, 2025 (CC BY 4.0). https://open.lib.umn.edu/animaldermatology/chapter/otitis-externa-dogs-and-cats/
- Torres SMF, et al. 2.11 Otitis Media: Dogs and Cats. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota Libraries Publishing, 2025 (CC BY 4.0). https://open.lib.umn.edu/animaldermatology/chapter/otitis-media-dogs-and-cats/