Angioimmunoblastic T-cell lymphoma (AITL) is a rare form of non-Hodgkin lymphoma, which is a group of related malignancies (cancers) that affect the lymphatic system (lymphomas). The lymphatic system functions as part of the immune system and helps to protect the body against infection and disease. It consists of a network of tubular channels (lymph vessels) that drain a thin watery fluid known as lymph from different areas of the body into the bloodstream.
Lymph accumulates in the tiny spaces between tissue cells and contains proteins, fats, and certain white blood cells known as lymphocytes. As lymph moves through the lymphatic system, it is filtered by a network of small structures known as lymph nodes that help to remove microorganisms (e.g., viruses, bacteria, etc.) and other foreign bodies. Groups of lymph nodes are located throughout the body, including in the neck, under the arms (axillae), at the elbows, and in the chest, abdomen, and groin. Lymphocytes are stored within lymph nodes and may also be found in other lymphatic tissues. In addition to the lymph nodes, the lymphatic system includes the spleen, which filters worn-out red blood cells and produces lymphocytes, and bone marrow, which is the spongy tissue inside the cavities of bones that manufactures blood cells. Lymphatic tissue or circulating lymphocytes may also be located in other regions of the body. There are two main types of lymphocytes: B-lymphocytes (B-cells), which may produce specific antibodies to "neutralize" certain invading microorganisms, and T-lymphocytes (T-cells), which may directly destroy microorganisms or assist in the activities of other lymphocytes.
AITL results from errors in the production of a T-cell or transformation of a T-cell into a malignant cell. Abnormal, uncontrolled growth and multiplication (proliferation) of malignant T-cells may lead to enlargement of a specific lymph node region or regions; involvement of other lymphatic tissues, such as the spleen and bone marrow; and spread to other bodily tissues and organs. A key and differentiating aspect of AITL is dysfunction of the immune system, which can lead to a variety of symptoms. Individuals with AITL may develop a rash, persistent fever, unintended weight loss, tissue swelling due to the accumulation of fluid (edema) and additional symptoms. The exact, underlying cause of AITL is not fully understood.