One of the biggest questions about cancer is why it occurs. There is not one answer to this complicated question. In some cases, it is genetic, but in most it is a random event. Cancer arises from mutations of DNA which are not repairable. These mutations occur due to the natural aging process, environmental causes (such as cigarette smoke and lung cancer), UV exposure, and viruses. In animals, it is never due to the food you are feeding, flea/tick products, or something you did to cause it to happen.
If your vet is concerned that your pet has cancer, I recommend doing the testing to confirm the diagnosis. This is usually done by obtaining a sample for cytology or biopsy. Once a diagnosis is established then I can get involved to help. Cancer is a word that evokes strong emotions and feelings. Many of us know a family member or friend who have been diagnosed with cancer and it tends to instill great fear, but it does not need to be that way. My role as veterinary oncologist is to educate veterinarians and pet owners on the disease process and progression, discuss treatment options, promote hope and reasonable expectations, and esupport everyone through the journey. It is my goal to educate primary care veterinarians thoroughly to make the diagnosis less intimidating and more manageable at the local care level.