Lymphomas are malignancies of the lymph system that are generally subdivided into two groups: Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL). Hodgkin's disease accounts for about 10% of all lymphomas, and NHL for the remaining 90% of lymphomas.
Non-Hodgkin's lymphoma is a term for malignancies that range from a very slow disease to an extremely aggressive but curable condition. They have certain features in common.
The Lymphatic System
Lymphomas, such as non-Hodgkin's lymphomas and Hodgkin's disease, represent tumors of the lymphatic system. This system is a network of organs, ducts, and nodes. The lymphatic system interacts with the blood's circulatory system to transport a watery clear fluid called lymph throughout the body. The lymphatic system contains lymphocytes, important cells involved in defending the body against infectious organisms.
Lymphocytes. The lymphatic system is involved in the production and transportation of lymphocytes, white blood cells that are an essential part of the immune system:
- Lymphocytes develop in the bone marrow or thymus gland and are therefore categorized as either B cells (bone marrow-derived cells) or T cells (thymus gland-derived cells).
- Lymphatic vessels begin as tiny tubes and lead to larger lymphatic ducts and branches until they drain into two ducts in the neck, where the fluid re-enters the bloodstream.
- Along the way, the fluid passes through lymph nodes, oval structures composed of lymph vessels, connective tissue, and white blood cells. Here, the lymphocytes are either filtered out or added to the contents of the node.
- Both leukemia and lymphomas (Hodgkin's disease and non-Hodgkin's lymphomas) are cancers of lymphocytes. The difference is that leukemia starts in the bone marrow while lymphomas originate in lymph nodes and then spread to the bone marrow or other organs.
Lymph Nodes. In lymph nodes, lymphocytes receive their initial exposure to foreign substances (antigens), such as bacteria or other microorganisms. This exposure activates the lymphocytes to produce antibodies, which are immune system factors that target and attack specific foreign proteins (antigens). The size of a lymph node varies from that of a pinhead to a bean. Most nodes are in clusters located throughout the body. Important node clusters are found in the neck, lower arm, armpit, and groin.
Other Structures in the Lymphatic System. The tonsils and adenoids are secondary organs composed of masses of lymph tissue that also play a role in the lymphatic system. The spleen is another important organ that processes lymphocytes from incoming blood.
Click the icon to see an animation detailing the lymph nodes.
Click the icon to see an image of lymph tissue in the head and neck.
Click the icon to see an image of the immune system structures.
Locations of Non-Hodgkin's Lymphomas
Non-Hodgkin's lymphomas occur most often in lymph nodes in the chest, neck, abdomen, tonsils, and the skin. NHL may also develop in sites other than lymph nodes such as the digestive tract, central nervous system, and around the tonsils.
Non-Hodgkin's Lymphomas Categories
There are more than 30 distinct types of non-Hodgkin's lymphomas. Lymphomas are categorized in a several ways:
Indolent (slow-growing) or aggressive (fast-growing). Indolent and aggressive lymphomas are equally common in adults. Aggressive lymphomas are more common in children. Aggressive lymphomas tend to be more curable than indolent lymphomas.
- B cell or T cell. About 85 to 90% of Non-Hodgkin's lymphomas are B-cell subtypes and 10 to 15% are T-cell subtypes. This report focuses on B-cell lymphomas.
The following are common types of B-cell lymphoma.
Diffuse Large B-Cell Lymphoma (DLBLC). DLBCL is the most common type of non-Hodgkin's lymphoma, accounting for about 30% of all NHL cases. It is an aggressive, fast-growing lymphoma that usually affects adults but can also occur in children. DLBCL can occur in lymph nodes or in organs outside of the lymphatic system. DLBCL includes several subtypes such as mediastinal large B-cell lymphoma, intravascular large B-cell lymphoma, and primary effusion lymphoma.
Follicular Lymphoma (FLs). Follicular lymphoma is the second most common type lymphoma, accounting for about 20% of all NHL cases. It is usually indolent (slow growing), but about 20 to 50% of follicular lymphomas transform over time into the aggressive diffuse large B-cell lymphoma.
Mantle Cell Lymphoma. Mantle cell lymphoma is an aggressive type of lymphoma that represents about 7% of NHL cases. It can be a difficult type of lymphoma to treat and often does not respond to chemotherapy. It is found in lymph nodes, the spleen, bone marrow, and gastrointestinal system. Mantle cell lymphoma usually develops in men over age 60.
Small Lymphocytic Lymphoma (SLL). SLL is an indolent type of lymphoma that is closely related to B-cell chronic lymphocytic leukemia (CLL). It accounts for about 5% of NHL cases.
Marginal Zone Lymphomas (MZL). MZLs are categorized depending on where the lymphoma is located. Mucosa-associated lymphoid tissue lymphomas (MALT) usually involve the gastrointestinal tract, thyroid, lungs, saliva glands, or skin. MALT is often associated with a history of an autoimmune disorder (such as Sjögren syndrome in the salivary glands or Hashimoto's thyroiditis in the thyroid gland). MALT is also associated with bacterial infection in the stomach (H. pylori) and can be potentially cured by antibiotics when treated in its early stages. Splenic marginal zone lymphoma affects the spleen, blood, and bone marrow. Nodal marginal zone B-cell lymphoma is a rare type of indolent lymphoma that involves the lymph nodes.
Lymphoplasmacytic Lymphoma. Lymphoplasmacytic lymphoma, also called Waldenstrom's macroglobulinemia or immunocytoma, is a rare type of lymphoma accounting for about 1% of NHL cases. It usually affects older adults and most often involves bone marrow, lymph nodes, and spleen.
Primary Central Nervous System Lymphoma. This lymphoma affects the brain and spinal cord. Although it is generally rare, it is common in people who have AIDS.
Burkitt's Lymphoma. Burkitt's lymphoma is one of the most common types of childhood NHL, accounting for about 40% of NHL pediatric cases in the United States. It usually starts in the abdomen and spreads to other organs, including the brain. A specific type of Burkitt's lymphoma that typically occurs in African children often involves facial bones and is associated with Epstein-Barr virus infection.
Lymphoblastic Lymphoma. This lymphoma is also common in children, accounting for about 25% of NHL pediatric cases, most often boys. It is associated with a large mediastinal mass (occurring in chest cavity between the lungs) and carries a high risk for spreading to bone marrow, the brain, and other lymph nodes.