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Immune System Tumors in Dogs

By Christine Andreoni, , Senior Manager, Department of Immunology, Discovery Merial Limited
Kevin T. Schultz, DVM, PhD, Chief Scientific Officer, Head of Global Research and Development, Merial Limited

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Cancer occurs when cells grow out of control. This can happen with the cells of the immune system. 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, which causes a tumor 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, liver, and other organs.

The signs of lymphoma are related to the location of the tumor(s). The only signs of tumors that develop in the lymph nodes are swelling of the nodes. The gastrointestinal form is often accompanied by vomiting, diarrhea, 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. These bumps can itch or be reddened. 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, but remissions of 1 year or longer are common with chemotherapy.

Location of lymph nodes in the dog

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