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Lymphosarcoma (Lymphoma) in Dogs

By: Dr. Kimberly Cronin

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Lymphosarcoma (lymphoma) is a malignant cancer that involves the lymphoid system. In a healthy animal, the lymphoid system is an important part of the body's immune system defense against infectious agents such as viruses and bacteria. Lymphoid tissue normally is found in many different parts of the body including lymph nodes, liver, spleen, gastrointestinal tract and skin. Lymphosarcoma is classified according to the location in the body in which the cancer begins.

These include:

  • The multicentric form occurs in the lymph nodes.

  • The gastrointestinal form occurs in the stomach, intestines, liver and lymph nodes in the abdomen.

  • The mediastinal form occurs in the mediastinum, in front of the heart in an organ called the thymus. Hence this form of lymphosarcoma sometimes is called thymic lymphoma.

  • The cutaneous form occurs in the skin.

  • Acute lymphoblastic leukemia occurs when the disease starts in the bone marrow.

  • Miscellaneous forms of lymphosarcoma are less common and include those that begin in the nervous system, nasal cavity or kidneys.

  • In dogs, the most common form of lymphosarcoma is the multicentric form (80 percent of all dogs with lymphoma have this form). Frequently, owners notice lumps under the neck or in other locations. These lumps represent the enlarged lymph nodes. Dogs still may feel normal at this point in the disease or may have vague symptoms such as lethargy or decreased appetite. The other forms of lymphosarcoma are much less common in dogs.

  • Lymphosarcoma occurs in middle-aged to older dogs. Breeds of dogs that are at a higher than average risk of developing this disease include Rottweilers, Scottish terriers, Golden retrievers, Basset hounds, and German shepherds. Males and females are affected equally. In dogs, there may be a genetic basis for this disease and, in certain breeds, some families several closely related animals have been affected. An association between development of lymphosarcoma and exposure to the herbicide 2,3-D may exist.

  • Symptoms with lymphosarcoma depend on primarily on the location of the tumor cells. Symptoms include enlargement of external lymph nodes, vomiting, diarrhea, loss of appetite, weight loss, lethargy, difficulty breathing and increased thirst or urinations. Cutaneous lymphosarcoma can cause redness or flakiness of the skin, ulceration (especially near the lips and on the footpads), itchiness or lumps in the skin.


  • Fine needle aspirate and microscopic analysis of an enlarged lymph node.

  • Biopsy of a lump or enlarged lymph node.

  • Endoscopy and biopsy of the gastrointestinal tract.

  • Fine needle aspiration and microscopic analysis of bone marrow to evaluate for invasion of malignant lymphocytes into the bone marrow.


  • Chemotherapy (most common form of treatment)

  • Radiation therapy (for localized disease)

  • Surgery (for localized disease)

    Home Care

    Seek veterinary care promptly if you detect lumps below your pet's skin in the neck, shoulders, armpits, or back legs or if your pet has vague symptoms of illness such as loss of appetite, lethargy, and weight loss. Watch your pet for vomiting, diarrhea and development of infections.

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