What Is Cancer?
Cancer, also called neoplasia, is the uncontrolled replication of undifferentiated cells. Healthy cells in the body have DNA that defines their purpose. For example, a bone cell looks and acts differently than a liver cell. This cellular DNA also helps cells grow and replicate in a normal fashion, only replicating when new cells are needed to replace old or damaged cells. However, when DNA becomes damaged or mutated, the cell's ability to mature into a healthy cell and replicate may be impaired. This can result in cells replicating out of control, forming a mass of immature cells — a tumor.
What is a lipoma?
A lipoma is a large benign tumor comprised of fat cells, but it has nothing to do with whether a dog is fat or thin. A soft swelling, lipomas are smooth, round, and movable. They usually grow on the rib cage and body but can be found anywhere, including an eyelid or in the armpit. They seldom cause problems.
Not all tumors are cancerous. Tumors can be benign, meaning they do not invade surrounding tissues and they can usually be removed and will not grow back. Tumors can also be malignant, meaning that they might invade surrounding tissues and can metastasize to distant organs and cause systemic disease. Not all cancers form tumors; for example, leukemia is a cancer of blood and bone.
Types of Cancer
Canine cancers depend on the types of cells in the body. Lymphosar-coma (lymphoma) is a highly malignant cancer of lymphocytes that can affect the lymph nodes, spleen, liver, gastrointestinal tract, and bone marrow. The average dog with lymphosarcoma is between six and nine years of age, although dogs of any age can be affected.
Nearly 85 percent of bone tumors in dogs are osteosarcomas, and 10,000 new cases of osteosarcoma are diagnosed every year in the United States. Osteosarcomas are highly aggressive tumors that usually affect the limbs of giant and large dogs but can also occur in the skull, ribs, vertebrae, and pelvis of smaller dogs.
Sarcomas are cancerous tumors formed from connective tissue within the body beneath the skin. Adenoma tumors are noncancerous and form from the cells lining the inside of an organ. They can arise from most of the gland cells in the body. Carcinomas are cancerous tumors arising from skin cells and the cells lining different organs.
Hemangiosarcoma is an aggressive soft tissue cancer of the lining of blood vessels that most commonly affects the spleen, heart, and the tissue under the skin. Using the body's blood vessels and producing its own blood vessel network, it spreads rapidly and produces other tumors throughout the body. This silent killer most commonly affects older, large breed dogs.
Anal sac adenocarcinomas occur mostly in female dogs older than about ten years of age. These tumors arise from the glands on either side of the rectum. Symptoms include straining to have bowel movements and enlarged lymph nodes in the pelvic area.
Mast cell tumors are most often malignant. Dogs of any age may develop them and they occur anywhere on the body as well as internally. They usually appear as raised red areas of hair loss on the skin. These masses may feel soft to solid.
Dogs with dark skin are prone to melanomas. These arise from pigment-producing cells that are responsible for coloring the skin and may be tied to genetics.
