What is mammary hyperplasia?

Mammary hyperplasia in cats (also called fibroadenomatosis) is a benign condition characterized by a sudden and excessive growth of mammary tissue. This abnormal enlargement is linked to an inflammatory response, usually triggered by high levels of the hormone progesterone.

Progesterone causing this condition can be:

• Endogenous: produced naturally by the ovaries.
• Exogenous: introduced via hormone-based treatments given to the cat.

This condition mostly affects young, unspayed females during their first heat cycles, typically between 3 months and 2 years of age. However, rare cases have been seen in prepubescent kittens, spayed females, and even male cats.

Symptoms of mammary hyperplasia in cats

The most obvious sign is the rapid swelling of the mammary glands. Other symptoms may include:

• Lethargy and decreased appetite, indicating discomfort
• Fever and sensitivity to touch
• Inflammation of the nipples, with or without unusual milk discharge
• Risk of ulceration and infection due to excessive licking

Veterinary monitoring is crucial to track the disease and prevent secondary infections or complications.

How is mammary hyperplasia treated?

Spontaneous recovery is rare, and complications are common. Treatment is strongly recommended.

Eliminating progesterone exposure

The key to resolving mammary hyperplasia is to remove the source of progesterone. Depending on the case, two scenarios exist:

• If the cat is on progesterone-based medication, immediate discontinuation is advised.
• If the hormone is naturally produced, spaying (ovariohysterectomy) is the most effective solution.

Alternative for breeding cats

For cats intended for reproduction, medical treatment that blocks progesterone may be considered. Unfortunately, this medication is not available in Canada, though a vet may apply for special import from Europe through Health Canada in select cases.

Recovery and monitoring

Once treatment is in place, mammary glands usually shrink within 3 to 4 weeks. Recurrence is rare when progesterone exposure is properly addressed. If medical therapy is used instead of surgery, the cat may return to breeding once fully recovered.

Conclusion

Mammary hyperplasia in cats is a benign but potentially problematic condition due to the risk of complications. Early diagnosis and proper treatment lead to a quick and successful recovery. If your cat shows sudden mammary swelling, consult your veterinarian promptly to begin the best treatment plan.