Lymphoma is a diverse group of cancers that originate in lymphocytes (a type of white blood cell) in the immune system. The commonly affected sites are lymph nodes, spleen and bone marrow, but lymphoma can occur in almost any tissue in the body where there is lymph tissue such as the gastrointestinal tract, eyes, central nervous system, bone, testes, bladder, heart, and nasal cavity.
Lymphomas typically affect middle-aged dogs (6-9 years old) and one of the most common cancers in the dog. Multicentric lymphoma (affecting many lymph nodes in the body) is the most common type of lymphoma in the dog and accounts for approximately 80% of all lymphoma cases. The symptoms vary and will depend on the cancer’s location and how advanced it is. Commonly observed findings are painless swollen lymph nodes, enlarged spleen and bone marrow involvement. The dogs may also show nonspecific signs such as lack of appetite, weight loss, vomiting, diarrhea, shortness of breath, increased thirst, increased urination and fever. Dogs with gastrointestinal lymphoma can experience vomiting, diarrhea, weight loss, and lack of nutrient absorption.
Dogs with lymphoma in their chest cavity can have edema (swelling) of their neck, head or front limbs. Dogs with skin lymphoma will show tumors that appear as nodules, plaques, ulcers or dermatitis (inflammation of the skin). Dogs with lymphoma in their central nervous can experience seizures, paralysis, and partial loss of movement. Dogs with eye lymphoma show infiltration and thickening of the iris, eye inflammation, blood in the eye, presence of puss, or glaucoma.
The veterinarian needs a thorough history of your dog’s health and onset of symptoms. Once the initial history has been taken, a complete physical examination is performed on your dog. Routine laboratory testing includes a complete blood count, biochemistry profile, and urinalysis. The blood tests may reveal anemia, abnormally low levels of lymphocytes in the blood (lymphopenia), an abnormally high number of neutrophils (a type of white blood cell) in the blood (neutrophilia), an abnormally high number of monocyts (a type of white blood cell) in the blood, and abnormally low numbers of platelets (cells that are important in blood clotting), a condition called thrombocytopenia. The biochemistry profile may show abnormally high levels of liver enzymes and calcium, a common finding with lymphomas. Urinalysis results are usually found to be at normal levels in these patients. More specific testing may be required for a confirmatory diagnosis. Diagnostic imaging, including X-rays and ultrasound, are often used to evaluate the size of regional lymph nodes.
Your veterinarian will take bone marrow samples to be sent to a veterinary pathologist for further evaluation and to determine the extent of disease.