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Types of Cancer > Lymphomas > Non-Hodgkin's Disease > Overview
Non-Hodgkin's Lymphomas: The Basics
Carolyn Vachani RN, MSN, AOCN
Affiliation:
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: February 27, 2007
What is the lymph system, and what are lymph nodes?
The lymph system is essentially the "housekeeping system" of the body. It is a network of vessels (tubes), which connect the lymph nodes. These nodes can vary in size, but are normally up to about 2 centimeters in width. They contain cells that clear bacteria and other foreign debris from the body. Lymph is a watery liquid that flows between cells in the body, picking up foreign debris and taking it into the lymph node for filtering. From the lymph node, the debris may pass through several more nodes in the system before being dumped into the bloodstream to ultimately be cleared by the liver. The lymph system flows throughout the body, and also includes the spleen and thymus gland.
What is a lymphocyte?
Lymphocytes are a type of white blood cell. These cells (called B cells and T cells) are important in fighting infection and mount what is called the "immune response". B cells produce proteins called antibodies, which move through the bloodstream and attack a specific target as directed by the B cell. They start their lives in the bone marrow and then develop fully in the lymph nodes. T cells are developed in the thymus gland and directly attack the cells identified as foreign by the B cells. In addition, both of these cells are able to remember bacteria from previous infections, and thus respond quicker to future infections.
What are the non-Hodgkin's lymphomas?
Simply put, the non-Hodgkin's lymphomas (NHLs) are a group of cancers that affect the immune system, the very system that is supposed to protect our body against disease. NHLs begin in the lymph nodes and are made up of malignant (cancerous) lymphocytes (either B cells or T cells). In 2001, the World Health Organization developed a comprehensive classification system for the 30+ different types of non-Hodgkin's lymphomas (NHLs), which are then further divided according to the cell type involved (either B cell or T cell). (See WHO classification at the end of this article) These 30+ types of NHLs are different in their growth rates and aggressiveness, and are often treated differently.
In the U.S., B cell lymphomas account for about 90% of all NHL cases, but this rate varies in different regions of the world. Nationally, there are approximately 66,000 new cases each year, making NHL the fifth most common cancer in both men and women. Rates have been increasing 3-4% annually in the U.S. since the 1950's, but incidence varies widely throughout the world. For instance, in the United Kingdom, there are approximately 10 cases for every 100,000 people, whereas in Asia there are only 2 cases for every 100,000 people, compared to approximately 20 per 100,000 in the U.S.
The non-Hodgkin's lymphomas should not be confused with Hodgkin's disease, as these are two distinct diseases. Although Hodgkin's disease also occurs in the lymph system, doctors are able to differentiate between the two because of the presence of Reed-Sternberg cells in Hodgkin's tumors. (Read about Hodgkin's disease in adults or in children).