These are the most common tumors found in female dogs, generally those that are older. If a dog is spayed prior to her second heat cycle, the risk decreases. Approximately half of all mammary canine tumors are malignant. They tend to grow and metastasize rapidly. Spaying or neutering at an early age greatly reduces the risk.
Mouth cancer is common in dogs, but less so in cats.
Because many of these swellings are malignant, early treatment is critical. Masses on the gums, bleeding, odor, or difficulty eating are warning signs. Nasal cancers may occur in both cats and dogs. Signs are bleeding from the nose, labored breathing, or facial swelling. These are skin tumors seen in middle-aged and old dogs and in older cats.