Cat Mammary Hyperplasia: Swollen Glands and Next Steps

What does mammary hyperplasia look like?

Rapid swelling around a cat's nipples can be mammary fibroadenomatous hyperplasia: benign, hormone-associated tissue growth, most often in young unspayed females. Enlarged glands can ulcerate and become infected. [1] Arrange a veterinary examination rather than deciding from a photograph that the swelling is harmless.

This article is general information, not a diagnosis for your cat.

The swelling may involve several glands rather than a single lump. Painful, enlarged glands can interfere with walking; reduced appetite and lethargy are also reported. [2] Record what you see without repeatedly pressing the tissue.

A mammary tumor remains an important alternative. Hyperplasia can mimic a tumor. [1] Softness, symmetry, or rapid growth should not become a home test for cancer.

Why reproductive and medication history matters

Tell the vet whether your cat is spayed, could be pregnant, or has recently shown heat behavior. Young cycling and pregnant queens are typical patients, but cats given progestin medications can also develop this condition. [3]

Bring every medication name, including injections used to suppress heat, and the date it was given. A published case series described hyperplasia after depot medroxyprogesterone acetate; its hormonal influence persisted after neutering. [5] Do not assume a previous injection has stopped affecting your cat because she has since been spayed.

What the vet may check and what you can do safely

The vet combines the examination with reproductive and drug history. Pregnancy should be investigated, and a spayed cat may need assessment for remaining ovarian tissue. [2] A tissue biopsy can confirm hyperplasia when the diagnosis is uncertain, although very swollen tissue can be difficult to close and heal. [3]

Before the visit, take a clear photograph, note which areas are enlarging, and record appetite, activity, walking, and any discharge. Bring earlier photographs if available. Do not squeeze nipples, puncture the swelling, or apply leftover medication. Ask the clinic how to protect an open area during transport and whether the next prescribed hormone dose should be withheld.

Removing the progesterone source, often through spaying, can resolve confirmed hyperplasia. [1] Treatment is a veterinary decision, not a reason to schedule routine surgery without first examining a swollen or unwell cat.

Your cat's reproductive history, medication exposure, and skin condition determine the next step; the word “benign” does not settle the urgency.

When to See a Vet

• Contact your vet promptly: any new swelling or lump beside a nipple, even if your cat is eating and seems comfortable.
• Request a same-day assessment: the swelling is visibly enlarging, your cat avoids being touched, or walking is affected.
• Seek urgent same-day care: skin has opened, there is bleeding or discharge, or your cat is repeatedly licking a damaged area.
• Seek emergency care now: your cat collapses, cannot stand, or is breathing with obvious effort; do not wait for a mammary appointment.

Frequently Asked Questions

Is mammary hyperplasia the same as cancer?

No. Confirmed hyperplasia is benign, but it can resemble neoplasia. [1] A new swelling needs examination, not a texture-based diagnosis.

Can male cats get mammary hyperplasia?

Yes. A published male-cat case was confirmed by mammary histology despite no recorded progestin treatment. [4] Sex alone does not exclude it.

Will mammary hyperplasia go away on its own?

Spontaneous regression can occur after the hormonal stimulus ends. [2] Do not wait for this without a diagnosis and a monitoring plan.

Can mammary hyperplasia be cured?

Removal of the progesterone source can resolve it. [1] Recovery and the treatment choice depend on the individual examination.

Can mammary hyperplasia come back after treatment?

Yes. A case report documented recurrence during a later pregnancy after successful medical treatment. [6] Discuss future breeding with your vet.

How much does treating mammary hyperplasia cost?

There is no reliable universal price. Ask for an itemized estimate covering examination, proposed testing, treatment, wound care, and follow-up, and clarify what might change it.

References

1. Edwards E. Cat diagnosed with mammary gland fibroadenomatous hyperplasia. Texas A&M Veterinary Medical Diagnostic Laboratory (professional diagnostic case study), 2024. https://tvmdl.tamu.edu/case-studies/cat-diagnosed-with-mammary-gland-fibroadenomatous-hyperplasia/
2. Giménez F, et al. Early Detection, Aggressive Therapy: Optimizing the Management of Feline Mammary Masses. Journal of Feline Medicine and Surgery, 2010. https://pmc.ncbi.nlm.nih.gov/articles/PMC10829160/
3. Little S. Feline Reproduction: Problems and clinical challenges. Journal of Feline Medicine and Surgery, 2011. https://pmc.ncbi.nlm.nih.gov/articles/PMC11107981/
4. Mayayo SL, et al. Mammary fibroadenomatous hyperplasia in a male cat. JFMS Open Reports, 2018. https://pubmed.ncbi.nlm.nih.gov/29568542/
5. Loretti AP, et al. Clinical, pathological and immunohistochemical study of feline mammary fibroepithelial hyperplasia following a single injection of depot medroxyprogesterone acetate. Journal of Feline Medicine and Surgery, 2005. https://pmc.ncbi.nlm.nih.gov/articles/PMC10911546/
6. Maneeganondh N, et al. Recurrent Feline Mammary Fibroadenomatous Hyperplasia in a Cat During Gestation. Veterinary Medicine and Science, 2024. https://pmc.ncbi.nlm.nih.gov/articles/PMC11450970/