Normal anatomy and the development of non-hodgkin lymphoma

All blood cells start as stem cells in the bone marrow. Stem cells then mature into a variety of different blood cell types that have specific functions in the body. Non-Hodgkin lymphoma is an abnormality with a type of white blood cell called a lymphocyte. There are different types of lymphocytes, but the main types are:

• B-cell—Makes antibodies that help the body identify foreign substances in the body. The sooner the substance is identified, the sooner the immune system can work on eliminating it.
• T-cell—T-cells have a number of jobs including destroying invading bacteria and viruses, stimulating an immune response, or slowing an immune response.
• Natural killer (NK)—NK cells defend the body against invading viruses and cancer cells.

The lymphatic system is a network of fluid, vessels, organs, and lymph nodes throughout the body that carry fluids and immune cells throughout the body. Lymphoid tissues and organs include:

• Lymph fluid—Clear fluid made up of plasma (a blood component that comes from general circulation), lymphocytes, cellular by-products, and proteins.
• Lymph vessels—Fluid from spaces between the cells and other bodily structures is collected by lymph capillaries (microscopic vessels) and moved into larger lymph vessels. Lymph is moved toward the heart by lymphatic and muscular contractions. The lymph is filtered through lymph nodes and eventually returned to the blood supply by draining into large veins near the collarbone.
• Lymph nodes—Lymphoid tissue that contains lymphocytes and other immune system cells. Lymph nodes are scattered throughout the body in clusters. Lymph vessels pass through lymph nodes. As lymph passes through, it is filtered for foreign bodies, including cancer cells. Lymph nodes can become swollen or painful when the body is fighting an infection.
• Bone marrow—All blood cells start as stem cells and are formed in bone marrow. Stem cells can mature into a variety of different blood cell types that have specific functions in the body.
• Spleen—Located under the rib cage on the left side of the body. The spleen helps the body fight infection by making lymphocytes and other immune system cells. It filters out cellular by-products from circulation. The spleen also removes and destroys old, damaged red blood cells.
• Thymus—Located behind the breastbone in the middle of the chest. The thymus makes T-cell lymphocytes where they stay until they are matured.
• Adenoids and tonsils—Located in the back of the throat. Tonsils make lymphocytes. They offer protection against foreign bodies that are inhaled or swallowed.

Lymphatic tissue can also be found throughout the body in the digestive tract, nervous system, and skin.

Lymphatic Tissue and Organs

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With non-Hodgkin lymphoma, there is an excessive development abnormal lymphocytes. The cancerous cells are not able to carry out their normal function. The abnormal lymphocytes can also crowd out healthy cells in the lymph nodes decreasing the number of effective cells and weakening the immune system. Cancerous blood cells also circulate in the blood and lymph systems and can gather in organs like the spleen, bone marrow, lungs, and liver.

Types of lymphoma

Lymphoma is a cancer of a type of blood cell called white blood cells. Nearly all non-Hodgkin lymphomas develop in a type of white blood cell known as the B-cell lymphocytes. Other types of non-Hodgkin lymphoma arise from other white blood cells known as T-cell lymphocytes and NK cells. There are approximately another 60 subtypes of lymphomas that are determined by how the cancer cells appear under a microscope, the type of cell the cancer starts in, the presence of specific proteins, and its DNA make-up. These characteristics will help determine treatment steps and prognosis.

Non-Hodgkin lymphomas are also described by the rate of disease progression:

• Indolent—Slow-growing, often without symptoms. Indolent lymphomas can be managed, but are generally not curable.
• Aggressive—Fast-growing, often with symptoms (sometimes severe). Aggressive lymphomas can be treated and are generally curable.

Lymphomas grow and develop differently, which affects the choice and course of treatment.