Nipple Discharge in Cats: False Pregnancy, Mastitis, Tumor

Nipple discharge in a cat is a 3-way split, and the color tells you which branch you are on before any test is run. Thin white or cream fluid from several glands in an unspayed queen that has not been pregnant is milk, and the cause is a hormonal false pregnancy that needs no drug. Thick yellow, green, or blood-tinged fluid from 1 hot, hard gland with a fever of 40 C is mastitis and needs antibiotics inside 24 hours. Bloody or clear-straw fluid from a firm lump in a cat over 8 is a tumor until a needle says otherwise. About 85 to 90% of mammary lumps in cats are malignant, which is why the third branch is the one that cannot wait.

Read the fluid before you read anything else

What comes out	Most likely cause	Glands involved	Fever	Act within
Thin white or cream, both sides	False pregnancy	4 to 8 glands, symmetric	None, under 39.2 C	7 days, routine visit
Thick yellow or green, 1 gland	Mastitis, bacterial	1 to 2 glands, hot and firm	40 to 41 C	24 hours
Pink to bloody, 1 gland	Tumor or duct papilloma	1 gland, hard lump 1 cm and up	None	3 to 7 days, needle first
Brown or grey, foul smell	Abscess that has drained	1 gland, painful, skin thin	39.5 to 40.5 C	Same day
Clear or straw, watery	Duct ectasia, hormonal	1 to 3 glands	None	2 weeks, monitor size

False pregnancy: day 40 to day 90

A queen ovulates without conceiving, and the corpus luteum keeps producing progesterone for about 65 days, which is why the body behaves as if a litter is due. Mammary tissue swells from day 25 to 30, milk appears around day 35 to 45, and nesting behavior runs 1 to 3 weeks before it fades. The whole episode resolves by day 60 to 90 in most queens with no treatment at all. Two mistakes make it worse: expressing the milk, which raises prolactin and keeps production going, and cutting food to stop milk, which does nothing except thin the cat. Warm compresses for 5 minutes twice a day and a cone for 10 to 14 days to stop self-nursing cover most cases. The full timeline sits in false pregnancy in queens.

Mastitis: fever plus a hard, hot gland

Bacterial mastitis is the branch that can turn septic in 48 hours. Signs that separate it from a false pregnancy: 1 or 2 glands instead of all of them, skin that is red to purple, milk that is clotted or blood-streaked, a gland that feels like a hot stone, and a rectal temperature of 40 to 41 C with the cat off food. Kittens on that gland get diarrhea and fail to gain, so pull them off and hand-feed every 3 to 4 hours. The vet runs a milk culture, then starts amoxicillin-clavulanate at 12.5 to 25 mg/kg twice a day for 10 to 14 days while the culture grows. An abscess needs lancing and flushing every 24 to 48 hours. Gangrene of the teat, with black skin and a 41 C fever, means surgery the same day.

Why the tumor branch is the urgent one

Mammary tumors are among the 3 most common tumors in queens, and 85 to 90% of them are malignant carcinomas, against roughly half in dogs. The average age is 10 to 12 years, about 50% of cats have more than 1 gland involved at diagnosis, and the tumors spread to the lungs early, which is why a chest X-ray is part of the first visit. Size drives survival: a lump under 2 cm at surgery carries a median survival near 2 years, while one over 3 cm drops toward 6 months. Surgery to remove the chain runs $1,200 to $3,000, and a 1 cm lump is a far cheaper operation than a 4 cm one.

The spay timing that changes the odds

Veterinary oncology texts commonly cite the risk of mammary carcinoma as roughly 7 times higher in intact queens than in queens spayed before their first heat. Spaying after the first heat cuts less, and after the second heat less again, so each cycle before surgery gives the tissue another round of progesterone exposure. A queen spayed at 6 months, before any heat, sits near the bottom of that scale; one spayed at 5 years has already banked most of the risk. This is not a reason to skip spaying an older cat, since removing the ovaries still stops pyometra and pregnancy, but it is the reason shelters spay at 4 to 6 months. Weigh the numbers against the surgery itself, which runs $150 to $600 in most clinics.

Male cats get discharge too

It is rare, which is exactly why it gets dismissed. A male cat with fluid from a nipple, or with breast tissue enlarged past 5 mm, needs a needle sample rather than a wait. Causes are hormonal imbalance from an intact tom, ductal hyperplasia, and carcinoma at 1 to 2% of the frequency seen in queens. Any discharge in a male, any blood, and any lump over 1 cm goes to the vet within a week.

Pus or blood: the first 24 hours

Hour 0 to 2: photograph the gland, the fluid on a white paper towel, and the cat's posture, then take a rectal temperature if the cat allows it. Hour 2 to 6: call the clinic, describe color, number of glands, and temperature, and ask for a same-day slot if the reading is 39.7 C or above. Hour 6 to 12: stop the kittens from nursing, clean the gland with 0.9% saline, and apply a warm compress for 5 minutes. Do not squeeze the gland to see how much pus comes out, because pressure pushes bacteria deeper into the duct and into the blood. Hour 12 to 24: start the prescribed antibiotic, note the volume of discharge in a log, and recheck the temperature at 8-hour intervals. Any cat with a temperature above 40.5 C, pale gums, or breathing over 40 breaths a minute goes to the ER, not the morning slot. Do not express milk to relieve pressure and do not apply ice to a hot gland. If the cat licked a lily or a dog flea product, check the toxin list before the visit; the same color logic at another site is in cat eye discharge.

Your next 3 steps

1. Note how many glands leak and the exact color today, since 1 gland and 6 glands point to different diagnoses. 2. Take a temperature; 39.7 C and up means a visit within 24 hours. 3. Book a needle aspirate for any hard lump, any bloody fluid, or any discharge lasting past 10 days, because a $60 to $150 sample is the cheapest test on this page.

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