AIDS-related lymphoma is a disease in which malignant (cancer) cells form in the lymph system of patients who have acquired immunodeficiency syndrome (AIDS).

AIDS is caused by the human immunodeficiency virus (HIV), which attacks and weakens the body's immune system. The immune system is then unable to fight infection and diseases that invade the body. People with HIV disease have an increased risk of developing infections, lymphoma, and other types of cancer. A person with HIV disease who develops certain types of infections or cancer is then diagnosed with AIDS. Sometimes, people are diagnosed with AIDS and AIDS-related lymphoma at the same time. For information about AIDS and its treatment, please see the AIDSinfo Web site.

Lymphomas are cancers that affect the white blood cells of the lymph system, part of the body's immune system. The lymph system is made up of the following:

• Lymph: Colorless, watery fluid that travels through the lymph system and carries white blood cells called lymphocytes. Lymphocytes protect the body against infections and the growth of tumors.
• Lymph vessels: A network of thin tubes that collect lymph from different parts of the body and return it to the bloodstream.
• Lymph nodes: Small, bean-shaped structures that filter lymph and store white blood cells that help fight infection and disease. Lymph nodes are located along the network of lymph vessels found throughout the body. Clusters of lymph nodes are found in the underarm, pelvis, neck, abdomen, and groin.
• Spleen: An organ that makes lymphocytes, filters the blood, stores blood cells, and destroys old blood cells. The spleen is on the left side of the abdomen near the stomach.
• Thymus: An organ in which lymphocytes grow and multiply. The thymus is in the chest behind the breastbone.
• Tonsils: Two small masses of lymph tissue at the back of the throat. The tonsils make lymphocytes.
• Bone marrow: The soft, spongy tissue in the center of large bones. Bone marrow makes white blood cells, red blood cells, and platelets.

Anatomy of the lymph system, showing the lymph vessels and lymph organs including lymph nodes, tonsils, thymus, spleen, and bone marrow. Lymph (clear fluid) and lymphocytes travel through the lymph vessels and into the lymph nodes where the lymphocytes destroy harmful substances. The lymph enters the blood through a large vein near the heart.

There are many different types of lymphoma.

Lymphomas are divided into two general types: Hodgkin lymphoma and non-Hodgkin lymphoma. Both Hodgkin lymphoma and non-Hodgkin lymphoma may occur in AIDS patients, but non-Hodgkin lymphoma is more common. When a person with AIDS has non-Hodgkin lymphoma, it is called an AIDS-related lymphoma.

For more information, see the following PDQ summaries:

• Adult Non-Hodgkin Lymphoma Treatment
• Childhood Non-Hodgkin Lymphoma Treatment
• Primary CNS Lymphoma Treatment