Immune System Tumors in Dogs

Cancer occurs when cells grow out of control. This can happen with the cells of the immune system. The tumor cells do not usually perform normal functions, which leads to immunodeficiencies.

The normal immune system requires a rapid increase in the growth of lymphocytes to fight foreign invaders. On occasion however, this increase in the growth of lymphocytes may be uncontrolled and can lead to the production of mutated cells, which causes a type of cancer called lymphoma. Lymphoma is one of the most common tumors in dogs. Boxers, Basset Hounds, and Rottweilers are predisposed to developing lymphomas, which primarily affect middle-aged and older dogs. Lymphomas can occur in the lymph nodes, spleen, chest, liver, kidneys, digestive tract, blood, skin, and other organs.

The signs of lymphoma are related to the location of the tumor(s). Most tumors develop in the lymph nodes, causing them to swell. If a dog has many tumors throughout the body, fever, lethargy, and weakness can be seen. The gastrointestinal form is often accompanied by vomiting, diarrhea, constipation, abdominal pain, weight loss, and lack of appetite. Signs of the chest form of lymphoma include shortness of breath and muffled heart sounds. The skin form has several different signs including single or multiple lumps in the skin or mouth. Lymphoma can also appear as scaly patches across the body.

Lymphoma can be diagnosed with a combination of blood tests, biopsies, and ultrasonography. The treatment for canine lymphoma often includes chemotherapy, usually with a combination of drugs. Adverse effects of the chemotherapy include vomiting, diarrhea, lack of appetite, and fever. Hair loss as an adverse effect of chemotherapy does not occur in dogs. Your veterinarian can advise you about the most appropriate treatment for your dog. Survival rates for dogs with lymphoma vary depending on the type of tumor, patient factors, and the type of treatment. More than 90% of patients with lymphoma of the lymph nodes will go into remission with chemotherapy. However, gastrointestinal lymphoma can be harder to manage. Radiation and surgical removal have also been shown to be effective for certain types of lymphoma.