Cancer is a common name given to a variety of unrelated diseases with different effects but with a similar and dangerous ability. Cancer cells escape detection by your pet’s usually protective DNA policing enzymes. They also trick the wonderfully named ‘natural killer cells’ of the immune system into not attacking and destroying them, into regarding the cancer cells as 'self'. Having eluded the body's natural defences, cancer cells embark upon an eternal life of producing countless generations of descendant cancer cells. Ultimately, all cancers develop because of damage to DNA.
Cancers are technically, malignant tumours. Malignant tumours are always dangerous and are classified according to where they originate. Carcinomas arise from the tissues that line the internal and external surfaces of a dog or cat's skin and organs while sarcomas arise from within tissues such as muscles, blood vessels and bones. Lymphomas develop from lymphoid tissue. These are not uncommon in older cats. Benign tumours are usually but not always harmless. The seriousness of a benign tumour depends on where it is located or whether it is hormone-producing. Lipomas, fatty tumours under the skin are the most common benign tumours in dogs and rarely causing harm. It can be difficult for us to differentiate between a benign tumour and a malignant or cancerous one, without examining some tissue from it, a biopsy, under the microscope. In cats, malignant tumours are unfortunately more common than benign ones.