According to the National Cancer Institute (NCI), the top five cancers in people are breast cancer in women, prostate cancer in men, followed by lung cancer, colon/rectal cancer, and melanoma in both sexes.
When it comes to our pets, there’s no national organization that tracks the occurrence of cancer. We do know that many common human cancers are not prevalent in pets, but there are other cancers we do acquire in common, including breast (mammary gland) cancer, lymphoma, skin cancer that takes the form of mast cell tumors in pets, and bone cancer
Mammary gland cancer
Mammary gland or breast cancer is common in both dogs and cats. It is the most common tumor found in female dogs and the third most common in cats. One of the benefits of early spaying of female pets is a decreased risk of mammary gland cancer.
Lymphoma is a cancer of the lymph system, which is part of the immune system. In cats, one in three cancer diagnoses is lymphoma, most often of the GI tract. Dogs also develop lymphoma.
Mast cell tumors
The most common type of skin cancer in pets is mast cell tumor (MCT). MCT is much more prevalent in dogs than in cats. In cats, mast cell tumors are most often seen in the skin of the head or neck, but they can occur anywhere in the body. Cats with these tumors are usually middle-age or older. Unfortunately, kitties with mast cell tumors on the inside of their bodies — typically in the GI tract or the spleen — carry a much poorer prognosis than tumors occurring on the skin.
In dogs, mast cell tumors are most often found on the trunk, limbs, and in between the toes. Prognosis depends on the tumor location, the extent of the tumor, the grade, and the type of treatment given. Mast cell tumors of the skin are very different in dogs than cats. Surgery to remove the tumor is less invasive in cats, and the prognosis for a full recovery is much better in cats than in dogs.
Mast cell tumors with generally poor prognosis are those on the muscle, around the mouth or in internal organs, in the bloodstream or bone marrow, and ulcerated tumors. Mast cell tumors that cause GI ulceration or are large, fast-growing, or recurring also carry a much poorer prognosis.
Bone cancer (osteosarcoma)
Osteosarcoma is a common and aggressive bone cancer that invades the long bones of large and giant breed dogs. Even with amputation of the affected limb and chemotherapy, which is the current standard of treatment, the average survival rate is only about a year.