Cats have eight nipples, which run along the underside of the body in rows of two. Both female and male cats have nipples. They are a pale pink in colour, and approximately 1cm in diameter. Nipples increase in size during both pregnancy and lactation. In the non-pregnant cat, they can be hard to find under the cat's thick layer of fur.
Swelling may occur in just one nipple or multiple nipples depending on the condition. Surrounding breast tissue may also be involved. Other common symptoms can include pain, redness, ulceration, lethargy, enlarged lymph nodes and loss of appetite.
What are the causes of nipple swelling in cats?
Pregnancy - A female cat's nipples will "pink up" and become swollen around the third week of pregnancy. This is perfectly normal.
Mastitis - This is an infection or inflammation of the mammary gland, occurring in lactating queens. Accompanying signs may include lethargy, loss of appetite, fever, the queen may refuse to nurse her kittens, if they are nursing, they may become sick. Treatment of mastitis is antibiotics. Painkillers may also be given. The queen's carer may be advised to use warm compresses on the area to assist with milk drainage.
Mammary cancer - The most common form of mammary cancer in cats is an adenocarcinoma, which is a fast growing tumour. This is seen most often in unspayed, older cats, (although it can affect spayed females and even male cats). It can occur in one gland but often several are affected. Typical symptoms of mammary cancer include swelling, ulceration and sometimes pain. Treatment is surgical removal of the affected glands and possibly chemotherapy.
Galactostasis - The abnormal collection of milk in the mammary glands usually caused by weaning. This should resolve in time.
Feline mammary hypertrophy - A benign tumour of the mammary gland. Seen most often in intact females, although it can also occur in intact males receiving hormones. Treatment includes spaying the female, or removal of the affected gland(s).
Mammary hyperplasia - This condition comes in two forms, Fibroepithelial Hyperplasia and Lobular Hyperplasia. The condition is caused by high levels of progesterone. Fibroepithelial hyperplasia occurs most often in young intact females who can experience enlarged mammary glands between 1-2 weeks after their first heat cycle. It can also affect males undergoing hormone therapy and spayed females. Lobular hyperplasia is usually seen in older, intact cats (aged between 1-14 years). Accompanying symptoms include pain, warmth, and ulceration. Treatment includes spaying the intact female if possible and withdrawal of progesterone treatment. Painkillers may be given if your cat is experiencing discomfort. If ulceration is present, the affected gland(s) may be surgically removed.
How is the cause of nipple swelling diagnosed?
Any swelling you notice on or around your cat's nipples should be investigated by a veterinarian. During the examination, he will perform a complete physical examination of your cat and obtain a medical history from you. He will check the nipples carefully, looking for swelling, pain, nipple colour, discharge etc. A nursing queen will be suspected of having mastitis (which is relatively common), he may want to run some diagnostic tests including taking a biopsy for evaluation. If cancer is suspected, chest and abdominal x-rays may be necessary to check for signs of metastasis (the cancer spreading). Other tests such as complete blood count, biochemical profile and urinalysis may be recommended to evaluate the overall health of your cat.