Mrs White was clearly anxious as she carefully lifted Snowy, her 11-year-old Bichon Frise, onto the table. “I was just giving her a morning tummy rub when I noticed it”, she explains, feeding Snowy treats as she speaks, “it’s definitely a lump, isn’t it? Is it cancer?” Mrs White gestures to Snowy’s tummy as she asks this question. 

The vet gives Snowy a full examination; checking her teeth, ears and eyes, heart and lungs, abdomen, limbs, skin and back end as well carefully feeling and assessing the lump that Mrs White has noted. Snowy is on the more senior end of the age spectrum at 11 years old and is decidedly overweight. She isn’t neutered, but is up to date with vaccine and parasite prevention. She eats well, and Mrs White says that she does drink quite a lot.

The vet finishes the check-up and has a chat with Mrs White. Apart from the lump, and Snowy’s weight, she appears to be in good health. Although the vet notes that her potentially increased thirst may be worth further investigation. The vet thinks that the lump may be a mammary tumour.

Mammary tumours in dogs

Mammary (breast) cancers in dogs are very common. They are most often seen in female dogs who have not been spayed. In fact, mammary cancer makes up around 50% of all tumours seen in intact female dogs1. The timing of neutering of female dogs can affect the likelihood of a mammary tumour: a study showed that these tumours occurred in 0.5% of females spayed before the first heat cycle, but that this increased to 8% or 26% when the animals were spayed after the first or second heat1.

Mammary masses can be benign, malignant or mixed. They appear as small nodules in the mammary glands, near the nipples. Occasionally, discharge may be seen from the nipple, or areas of soreness or redness on the skin. Malignant mammary cancers can spread to the lymph nodes, lungs or bone. 

The vet informed Mrs White that the lump was fairly likely to be a mammary mass, due to its location, and the fact that Snowy is an older, female, unspayed dog. She discussed performing a fine needle aspirate, to confirm whether the lump is a mammary mass. Unfortunately, an aspirate is not very accurate at determining whether the mass is malignant or benign, but it would hopefully confirm whether the nodule is a tumour or not.

Fine Needle Aspirate

A fine needle aspirate (FNA) is a procedure whereby a needle is inserted into a mass to sample a small amount of the cells within. The cells are then pushed out of the needle onto a slide and can be analysed under a microscope. The needle is a similar size to that used for a vaccination and this procedure is mostly well tolerated in dogs without the need for sedation or anaesthesia. The technique will not provide as much information as a surgical biopsy, but is much less invasive and is often used to provide some early information about a mass. 

Ultimately, the vet advised that surgical removal of the mass would likely be indicated, and it could then be sent away to the lab to determine exactly what type of mass it is. Mrs White was very concerned about putting Snowy under an anaesthetic at her age. The vet reassured her that Snowy appeared to be in good health for her age, but it was agreed to run some blood tests to check her internal organ function and also perform the FNA.

Snowy’s surgery

Two days later, Snowy’s results were in. The mass was confirmed to be a mammary tumour, and surgical removal was recommended. Snowy’s blood results and blood pressure were normal, with no particular concerns raised. Mrs White was still very worried about the anaesthetic and opted to have Snowy on an intravenous drip throughout the procedure, to support her blood pressure and organ function. The vet had discussed spaying Snowy, as mammary cancers are linked to entire females, but after discussion they decided just to remove the mass as a quicker operation and easier recovery, as well as sampling the lymph nodes and taking some x-rays of the lungs to check for spread of the cancer.

The cost of these tests and surgery was mounting up, but Mrs White had spoken to her insurance company who’d advised her that everything would be covered, including the blood tests, aspirate, x-rays and surgery.

Treating mammary cancer

The most common treatment method for mammary tumours is by surgical removal. The vet may remove the mass alone, or the entire gland, depending on the size and spread of the mass. If the cancer is malignant and has spread to other sites in the body such as the lungs, chemotherapy may be recommended. 

Mrs White was over the moon to hear that Snowy’s surgery had gone well. 

The lump was removed and sent away to the lab for analysis, along with samples from the nearby lymph nodes. Snowy’s chest x-rays were clear, with no sign of cancerous spread. There was more good news when the laboratory report came back. Snowy’s mammary mass was benign, and surgical removal was curative. 

Mammary cancer: prognosis

The prognosis for dogs with benign tumours which are surgically removed is excellent. For those with more malignant mammary cancer, prognosis depends on the size and stage of the tumour, and whether the dog is neutered. The stage and size of the tumour has a significant effect on survival out to two years after surgery2.

Snowy is now on a diet, but otherwise doing wonderfully for her 11 years. Mrs White’s veterinary costs were all covered by her insurance, which took that worry out of the equation and allowed her to focus on providing the best for her beloved pooch. She decided not to get Snowy spayed; but she now checks Snowy’s mammary region every few days for any problems


  1. Moe L. (2001) ‘Population-based incidence of mammary tumors in some dog breeds.’ J Reprod Fertil Suppl. (57): 439–443.
  2. Chang, S., Chang, C. Chang, T. & Wong, S. (2005) ‘Prognostic factors associated with survival two years after surgery in dogs with malignant mammary tumours: 79 cases (1998-2002) J Am Vet Med Assoc 227:1625–1629