With cats and dogs now living to older ages, cancer has become a leading cause of non- accidental death. Most cases occur between ages 10 and 12, but cancer can strike younger pets, too. Among the most common animal cancers are those of the reproductive system, such as mammary, uterine, and testicular cancer. Spaying and neutering early in life greatly reduces the risk of these cancers. Certain animals are also prone to skin cancer in regions of pale pigment or sparse hair growth, like a cat's pink nose or a dog's underbelly. Nasal sinus cancer appears much more often in dogs than in people, probably due to sniffing of toxins. The mouth is another possible site. Cancer can also develop in areas of chronic inflammation or past injury. Fibrosarcomas (fye-broh-sar-KOH-muhz) are tumors that may occur at vaccination sites in cats. Large or giant-breed dogs are especially susceptible to bone cancers, which often first appear as lameness. The good news is that many pet cancers are treatable with surgery, chemotherapy, or radiation. In addition, scientists are learning about new methods to fight the disease like gene therapy and tumor-encasing drugs. Remember, the earlier your pet is diagnosed, the better the chances for successful treatment, so see a veterinarian on a regular basis.