This is the most common tumour in cats and dogs. An unspayed female has a one in four chance of developing a mammary tumour. In dogs almost half of these are malignant. In cats most are. This risk is eliminated if a pet is spayed before her first season. Even spaying after one season still reduces her risk by over 90 percent.
Mammary tumours usually develop in pets over six years old. They are often multiple, occurring near one or more of the ten to 12 teats. While most are painless mobile masses, some individuals develop an invasive, painful inflammatory form, often in the glands closest to the groin. This form of breast cancer is very difficult to differentiate from an acute bacterial infection , a painful mastitis which responds well to antibiotics.
Malignant breast cancer spreads locally to regional lymph nodes or more widely, especially to the lungs. Chest x-rays should be taken before undertaking any radical breast surgery.
Breast lumps, together with surrounding normal tissue, should always be surgically removed and examined by a pathologist. If a pet has not been spayed she should be to deny any remaining cells their nourishing supply of female hormone although this will not increase the likelihood of a cure if a mammary cancer is malignant. Surgery offers a high cure rate for benign tumours, a moderate rate for small malignant tumours less than two cm in diameter and a poor cure rate for large or inflammatory forms of breast cancer. When surgery is not possible, chemotherapy or immunotherapy may enhance an individual's quality of life for a short while.
If you feel a lump in your dog or cat's breast tissue, don't procrastinate. See us as soon as practical.