Mammary Hyperplasia/Fibroadenoma Complex

author Sara Thornton DVM                 iCandy RagaMuffins 


Mammary hyperplasia is a condition recognized primarily in young cycling queens or in pregnant queens. It can also occur in any male or female cat that has been exposed to progestins, either accidentally or as a treatment. It appears as diffuse significant enlargement of one, or most likely, several or even all the glands. It causes marked discomfort for the cat due to the remarkable size the glands may achieve.

The cause of the disease, which goes by several monikers, is an amplified response to endogenous or exogenous progesterone. Affected glands become red, swollen, and in extreme cases, ulcerated. In the young  cycling queens and the pregnant queens, the glands are responding to the progesterone being produced by the cat. In these cases the condition will commonly subside without treatment in time. In other cases, the cat may be responding to the progesterone being used to treat a skin or behavior issue. In addition, cats exposed to a person’s hormone replacement therapy (HRT) gel, cream, or spray can develop fibroglandular hyperplasia. Another cause in a spayed queen is an ovarian remnant present after ovariohysterectomy.

Diagnosis is based on history and clinical signs.  The red, swollen glands may be difficult to distinguish from neoplasia, making cytology or a biopsy necessary in some cases. Generally, the cats are not febrile or painful except in cases where secondary infection sets in.

The treatment of choice for mammary hyperplasia in queens not destined for breeding is to spay them. In affected spayed cats, an LH test can be performed to determine if there is a small amount of ovarian tissue remaining. If that is the case, surgery can be performed to remove that tissue. In cases of HRT exposure, applying the dermal medicine to the person’s inner thigh usually helps prevent this exposure.   For the altered pet, a different medication can be used for treatment of skin or behavior so the offending medication can be discontinued.

There are a number of therapies that can be used to treat fibroglandular mammary hypertrophy for cats in breeding programs. These medications are not labeled for use in cats and often are not available except through compounding pharmacies. The progesterone receptor blocker aglepristine is the preferred treatment in many cases.  Cabergoline and bromocriptine are drugs that inhibit prolactin release from the pituitary gland, causing luteolysis, which in turn lowers endogenous progesterone levels.

In some cats, mammary hyperplasia resolves on its own over time. Secondary infections must be treated as needed. Even with treatment, it may take weeks to months to resolve.