Dogs have two kinds of sweat glands. Apocrine glands sit in the deeper skin across the body, while eccrine glands are found only in the footpads [1]. Most sweat gland tumors start in the apocrine glands [1].
Some of these tumors are benign (not cancer) and some are malignant (cancer). A vet cannot tell which by looking at or feeling the lump [4]. Only a sample from the lump can show the type.
Have your vet check any new lump on your pet’s skin.
Sweat gland cysts
Apocrine glands can also form fluid-filled cysts. In cats, a condition called cystadenomatosis causes cysts of the apocrine and ear glands, most often on the ears, and it is seen mostly in older cats [5]. In a study of 57 affected cats, both ears were usually involved, and a small share of the cats also had a cancer, which is one reason a vet may want a sample [5]. For more on cysts, see skin cysts in dogs.
Benign tumors: apocrine adenomas
Many sweat gland tumors in dogs are benign [1]. These adenomas usually show up as a single lump in an older pet [1][4]. Because a benign lump and a malignant one can look the same, a sample is still needed [4].
Dark lumps, for example on a cat’s ear, can also be other kinds of growth, such as pigment cell tumors. See skin melanoma in dogs and cats.
Malignant tumors: apocrine gland adenocarcinomas
The malignant form is called an apocrine gland adenocarcinoma. It is uncommon in both dogs and cats [1][2][3].
- Who: in an older study of 44 dogs and 10 cats, these tumors appeared in middle-aged and older animals. Golden Retrievers seemed to be at higher risk among dogs, while no breed or sex stood out in cats [4].
- Where: they can grow almost anywhere on the body, including the head, neck and legs [1][4]. In dogs the malignant type is found most often in the armpit and groin [1]. A recent case report described one on a cat’s lower lip [2].
- Look: they are usually a single lump [4]. Looks alone do not show whether a lump is benign or malignant [4].
Eccrine gland tumors on the footpads
Eccrine sweat glands are found in the footpads [1]. Tumors of these glands are described mainly in case reports. In two older cats with a malignant footpad tumor, the signs were limping and swelling of several toes, and in one cat the cancer had spread to the lungs [6].
How vets diagnose them
Your vet examines the lump and takes a sample. This can be a fine needle sample of cells or a biopsy, where a small piece of tissue is sent to a lab [2]. The lab result shows which type of tumor it is [2]. Your vet may also check nearby lymph nodes, because the malignant type can spread to them [1][2].
Treatment
Your vet will advise on treatment, which usually means surgery to remove the lump. For the malignant type, authors of a dog case report advise removing the tumor with a wide border of healthy tissue, because it can grow into nearby tissue or spread [1].
At home, as directed by a vet:
- note the size, place and date of any lump, so you can show your vet any change;
- do not squeeze or try to drain a lump;
- go back for every recheck.
Outlook
Outcomes vary between types:
- Adenomas: these are benign [1].
- Adenocarcinomas in dogs: they can come back where they were removed and can spread to nearby lymph nodes and the lungs, though spread to distant organs appears to be rare [1].
- Adenocarcinomas in cats: spread to nearby lymph nodes has been reported [2].
Because there are few reports, how often these tumors spread is still not well known [3]. These are statements about groups of animals. They cannot predict how one pet will do. Your vet can explain what this means for your pet.
When to see your vet
See your vet if your dog or cat has:
- a new lump anywhere on the skin [4];
- lumps or cysts on a cat’s ears [5];
- a lump or sore in the armpit or groin [1];
- a limp, swollen toes or a sore on a footpad [6].
FAQ
Is a fluid-filled lump always just a cyst?
No. Benign and malignant lumps can look alike, and some cats with ear cysts also had a cancer [4][5]. Your vet needs a sample to know.
Do sweat gland tumors spread?
The adenomas are benign [1]. The adenocarcinomas are malignant and can spread, most often to nearby lymph nodes [1][2].
Are these the same as ear canal (ceruminous gland) tumors?
They are related. The wax glands of the ear canal, called ceruminous glands, are a special type of apocrine sweat gland [7]. Tumors of those glands are covered in ceruminous gland tumors in dogs and cats.
The bottom line
Most sweat gland tumors grow from the apocrine glands in the skin. Many are benign, but the malignant type, apocrine gland adenocarcinoma, can grow into nearby tissue and spread to lymph nodes. In dogs it is found most often in the armpit and groin. A lump’s look does not show its type, so have your vet check any new lump.
This article is for general information only and does not replace advice from your veterinarian. If your pet has a new lump, see your vet.
Sources
- Moon CH, Min HA, Lee HB, et al. Retroperitoneal Metastatic Apocrine Gland Ductal Adenocarcinoma in a Beagle Dog. Veterinary Sciences, 2022 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC9143555/
- Park Y, Lee A, Jang J, et al. Feline Lower-Lip Apocrine Sweat Gland Adenocarcinoma with Mandibular Nodal Metastasis: A Case Report. Veterinary Sciences, 2026 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC13431336/
- Pescetelli LE, Misia AL, Moretti G, et al. Hypercalcemia of malignancy in a dog with cutaneous apocrine gland carcinoma and malignant myoepithelioma. Veterinary Research Communications, 2026 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC12819430/
- Kalaher KM, Anderson WI, Scott DW. Neoplasms of the apocrine sweat glands in 44 dogs and 10 cats. Veterinary Record, 1990. PubMed abstract. https://pubmed.ncbi.nlm.nih.gov/2267712/
- Loft KE, Soohoo J, Simon B, et al. Feline cystadenomatosis affecting the ears and skin of 57 cats (2011-2019). Journal of Feline Medicine and Surgery, 2022. PubMed abstract. https://pubmed.ncbi.nlm.nih.gov/34254846/
- Fuentealba IC, Illanes OG, Haines DM. Eccrine adenocarcinoma of the footpads in 2 cats. Canadian Veterinary Journal, 2000. PubMed abstract. https://pubmed.ncbi.nlm.nih.gov/10816835/
- Lavanya TR, Kumar P, Kok MK, et al. Ceruminous Gland Tumors in Canines and Felines: A Scoping Review. Animals, 2025 (CC BY 4.0). https://pmc.ncbi.nlm.nih.gov/articles/PMC12024219/