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Lymphosarcoma (lymphoma) is one of the most common cancers diagnosed in cats. It is a cancer of the lymphocytes (a type of blood cell) and lymphoid tissues. Lymphoid tissue is normally present in many places in the body including lymph nodes, spleen, liver, gastrointestinal tract and bone marrow.
The feline leukemia virus (FeLV) has been shown to cause lymphosarcoma in cats. We believe that the feline leukemia virus is responsible for many of the cases of lymphosarcoma. Cats with the feline immunodeficiency virus (FIV) are also at higher risk of developing lymphosarcoma. Cats of any age, breed and sex can be affected. We typically see lymphosarcoma in younger cats that are infected with the feline leukemia virus, and in older cats that are not infected with the virus.
Types of LymphosarcomaLymphosarcoma can be divided into several different forms, which depend upon the primary (predominant) site of the tumor. Some cats have multiple sites of involvement and do not fit well into just one category. These are usually animals with very advanced disease.Gastrointestinal tract: The most common form is involvement of the gastrointestinal tract. This includes the stomach, intestines and liver as well as some of the lymph nodes surrounding the intestines. Cats with this type of lymphosarcoma may have vomiting, diarrhea, weight loss or a decreased appetite.Mediastinal: The mediastinum is a term used for a special aggregation of lymphoid tissue in the chest. Cats with this type of lymphosarcoma often are seen because of difficulty breathing due to a large mass in the chest or an accumulation of fluid around the lungs.
Renal lymphosarcoma: The kidneys may be the primary sites of involvement. Cats that have this type are often seen because of signs related to kidney failure (increased thirst, increased urination, loss of appetite, vomiting).
Bone marrow: If the cancer were confined to the bone marrow, we would call this leukemia. The signs that we see in cats are usually related to the decreased numbers of normal cells (such as red blood cells that carry oxygen, white blood cells that fight infection and platelets that help with clotting) which are made in the bone marrow. Anemia, infections and bleeding are common problems.
External lymph nodes: In a few cats, the only site of involvement is the external lymph nodes. These cats may be seen because of problems such as vomiting and loss or appetite or because the owner noted "lumps" (enlarged lymph nodes) on their cat.
Other sites: We will occasionally see other sites such as the skin, nose, brain, and spinal cord as the primary site of involvement.
