What Is It: Cancer is a frequent problem in older pets. Mast cell tumors are the most common (and most fatal) type of cancer in dogs. Female pets that have not been spayed are prone to mammary tumors, which are often malignant and very hard to treat. Cancer, however, is not always fatal, especially when detected early and treated aggressively.
Symptoms: Weight loss, lethargy, weight loss, repeated infections, nausea, blood in the urine or stools, frequent infections, abdominal swelling, lumps, pain; many other symptoms associated to particular types of cancer.
Treatment: Surgery, chemotherapy, and radiation therapy.