Section: Overview
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.
Currently in the USA, gastrointestinal lymphoma is the most common form. Historically, mediastinal lymphosarcoma occurred most frequently in young cats infected with feline leukemia virus, but reports of young cats with FeLV positive lymphoma are less common than in the early 1980's. These cats may have involvement in other areas of the body, such as the bone marrow. The gastrointestinal form of lymphosarcoma most commonly affects older cats that are not infected with the feline leukemia virus.
Recently, research has shown that cats that live in smoking environments are 2 to 4 times more likely to develop lymphoma than cats that live in smoke-free environments. The exact mechanism is not understood.
Lymphosarcoma occurs in middle-aged to older cats. No breed of cat is known to be at a higher risk for lymphosarcoma than other breeds. Males and females of both species are affected equally. Infections with both feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) have been shown to increase the risk of developing lymphosarcoma. Cats infected with FeLV often develop lymphosarcoma at a young age.
Symptoms in cats with lymphosarcoma depend 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 (pruritus) or lumps in the skin.
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