Hearing the news that your pet has been diagnosed with cancer can be both devastating and terrifying at the same time. It is natural to have many questions about exactly what the diagnosis means, what might happen to your pet as the cancer progresses, and what options you have for treating the disease.
One of the most common questions I am asked by owners during an initial appointment is, “What caused my pet’s cancer?” I can definitely appreciate why this is an important piece of information they would want to understand. Unfortunately, this is a very difficult question to answer accurately, as in nearly all cases cancer is typically caused by a combination of genetic and environmental influences, many of which may have occurred years before the diagnosis was made.
The fact that certain types of cancers occur more often in particular breeds of dogs and cats lends much evidence to the concept of a genetic cause for the disease. We do know that the genetic mutations that cause cancer can occur in the reproductive cells of male and female animals, and these mutations can be passed on to puppies and kittens, giving rise to a heritable predisposition to different types of tumors. Most cancers, however, arise from mutations that occur to genes during a dog’s or cat’s lifetime that were not present at birth. These mutations can result from internal factors, such as exposure to naturally occurring hormones, or external factors, such as environmental tobacco smoke, chemicals, or even sunlight.