When and where they appear
In female dogs, mammary tumours can appear from 4 years of age, become fairly common from 7 years and are very common at 10 years and older. Tumours most often develop in the last two pairs of mammary glands, but all of the glands must be checked. In males these tumours are rare.
Spaying and risk
The likelihood of mammary tumours depends on when a female dog is spayed:
- before her first season, the risk falls to just 0.5%;
- between her first and second season, 8%;
- from her second season up to 2.5 years of age, 26%;
- spaying later than this no longer has much effect on the risk.
Earlier spaying also reduces the likelihood of mammary tumours in cats.
Siamese and Persian cats
Siamese and Persian cats have a higher risk of malignant mammary tumours and their spread (metastases). In these breeds, mammary tumours are almost always (in around 100% of cases) malignant. Malignant tumours grow quickly and unpredictably, so the cat needs regular preventive check-ups, especially if she is not spayed.
If you find a lump
If you feel a lump or a hard area on your pet's underside, be sure to see your vet. While mammary lumps are no larger than 0.5 cm, the outlook after removing them is good, and the chance of metastases or the tumour coming back is low.
If a mammary tumour is confirmed, depending on the animal's age and the size of the tumour, the following may be recommended:
- a chest X-ray, because mammary tumours most often spread to the lungs;
- biochemistry blood tests, to assess the anaesthetic risk properly.
Diagnosis and surgery
Whether a tumour is malignant or benign can be found out from a biopsy before surgery or from histology of the tumour afterwards. A biopsy before surgery tells the surgeon more about how wide a margin needs to be removed.
When mammary tumours are removed (mastectomy), the animal is spayed at the same time. This is especially important in cats, because hormones play a major role in the development of their mammary tumours.
Preventive check-ups, tests and mastectomy are available at Vilnius Vet clinics.
