Animal Cancer Update - Breast Cancer in Dogs and Cats

Breast cancer, usually mammary carcinoma, is a relatively common disease in dogs and cats that have not been desexed before 2 years of age. Animals desexed at or before 6 months of age have the lowest risks. Around 5 out of every 6 breast growths in cats and half in dogs, are malignant. This means that they are showing changes under the microscope which indicate the potential for the cancer to spread elsewhere in the body, and therefore to be fatal. Because these changes are only visible in relatively large sections of tissue removed from the lump, the first step that must be taken is removal of the lump itself. If the laboratory that analyses the tissue reports that the mass is a malignant cancer, then several things can be done. Firstly, sometimes more aggressive surgery may be necessary. Secondly, it is worth having x-rays or a CT scan of the lungs to see if the cancer is advanced. Note that if the scans do not show the tumour, it only means that the cancer is not advanced. (It takes around 500 million cancer cells to show up on an x-ray.) If the report from the laboratory shows specific changes that mean the tumour has very likely spread (or metastasised) then we assume that it has done so. Most dogs and cats with cancers in this category do not live more than 3-6 months without further treatment. Medical treatment has been shown to have the potential to dramatically reduce the numbers of cancer cells elsewhere in the body, meaning that the patients retain normal quality of life for significantly longer periods of time. The majority of patients do not have any side effects limiting their quality of life whilst they are receiving treatment. Treatment is not necessary for every patient, and can be costly.