What is lymphoma?
Lymphoma is a cancer of certain types of white blood cells (WBCs) called lymphocytes that localize in one or more lymph nodes. Lymphocytes circulate throughout the body in both the blood and the lymphatic system. The lymphatic system consists of a network of lymph nodes and vessels (lymphatics) that drain fluids from the tissues and carry them as "lymph" through the body and back to the bloodstream. Lymph nodes are found singly and in chains along the lymphatic vessels, in areas that include the neck, armpits, chest, abdomen, and groin. The nodes are small lymphoid tissue organs that filter lymph fluid as it passes through them and destroy microorganisms and abnormal cells. They contain macrophages and collections of lymphocytes, including B-lymphocytes, T-lymphocytes, and natural killer cells. Photo: Lymphatic system, Source: National Cancer Institute
T-lymphocytes can be thought of as the controllers of the immune system. They initiate the immune response, control how big or small it should be, and shut it down when it is not needed. In addition, they can neutralize several different types of foreign attackers. B-lymphocytes make antibodies. It is these cells that are activated when a person is vaccinated against diseases such as measles, mumps, or hepatitis. Natural killer (NK) cells are also a type of lymphocyte and make up about 10-15% of total lymphocytes in the blood. NK cells attack and "kill" abnormal cells such as cancer cells or those infected with viruses.
Any one of these cells or a combination of them can be involved in lymphoma. Lymphoma begins with the emergence of abnormal cells in one or more of the lymph nodes or lymphoid tissues. These cells reproduce uncontrollably, begin to outnumber normal cells in the node, lead to the enlargement of the lymph node, and eventually travel to one or more other lymph nodes. They may also spread to and from other lymph-system-related organs including the spleen, bone marrow, tonsils, adenoids, and thymus.
B-cell lymphomas are more common than T-cell lymphomas. For more about specific lymphomas, read the section on Types.