Lymphatics and Lymph Node Structure
The lymph system consists of a series of vessels, similar to blood vessels, and nodules called lymph nodes. The lymphatic vessels are spread throughout the body and carry lymph, a milky fluid filled with lymphocytes, the cells that control the immune system. The lymphatics pass through lymph nodes as they circulate through the lymphatic system. The lymphocytes can also leave the lymphatics to enter the blood stream and tissues and return to the lymphatics at any time.
Lymph nodes can be found throughout the body, including in the neck, armpits, middle of the chest, and back of the abdomen. Additional lymphoid tissue can be found in the tonsils, adenoids, thymus, bone marrow, spleen, lung, and areas in the gastrointestinal tract.
What is lymphoma?
Lymphoma is a tumour of lymphocytes. There are several different types of lymphocytes, the major types being the B-lymphocyte and the T-lymphocyte.
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’s 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 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 usually begins with the production of one or more abnormal cells in one or more of the lymph nodes, areas where lymphocytes congregate. 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.