As dogs reach their senior years, their risk of developing cancer rises. About half of all dogs over 10 years old get cancer, and the disease is among the most common causes of death in elderly animals. Like humans, canines can have all sorts of cancers, including lymphoma, skin, and breast cancers.
Cancer symptoms in dogs can be subtle or nonexistent, especially if the disease is in its early stages. One cancer sign involves the appearance of a suspicious bump on or under the skin. Veterinarians can biopsy such a mass to screen it for cancer.
Other, less definitive symptoms include weight loss and attendant problems like low appetite and difficulty eating. Dogs with cancer may also exhibit lethargy and problems going to the bathroom.