Overview

What is lymphoma?

The lymphomas (also called Hodgkin's lymphoma or Non-Hodgkin's lymphoma) are a group of cancers that usually begin in lymph nodes, which are bean-sized organs found all over the body. Wherever they are situated, lymph nodes normally increase in size to fight off infections. However, when lymphoma (cancer) cells develop, the lymph node enlarges and continues to grow as a tumor even if there is no infection. Non-Hodgkin's lymphoma (NHL) is the fifth most common cause of cancer in the United States with about 58,000 new cases diagnosed each year. People of any age can develop lymphoma.

Lymphoma may involve a group of lymph nodes in one or several regions of the body. Lymphoma cells can spill over into the blood (leukemia phase) and then spread to distant sites in the body. About 20 percent of lymphomas develop outside of lymph nodes, in specialized immune cell producing tissue within the spleen, digestive system, or skin.

The different types of lymphoma

A distinct type of lymphoma -- Hodgkin's lymphoma (Hodgkin's disease) -- is described in detail elsewhere on this site. Hodgkin's disease, unlike the NHLs, tends to progress predictably and is less likely to spread to other organs.

NHLs are classified by disease behavior, cell appearance, genetics and cell surface markers.

Disease behavior: NHLs are either aggressive or nonaggressive. The aggressive (high grade) NHLs progress very rapidly. They are more sensitive to chemotherapy and radiation therapy and are often cured. The nonaggressive NHLs, also called slow or indolent, progress very gradually and are sensitive to chemotherapy and radiation therapy. Patients with nonaggressive NHLs live many years but are less often cured.

Lymph node appearance. NHLs distort the normal lymph node structure. Two types of distortion -- called follicular (or circular) and diffuse -- depending on how they look under a microscope, account for about half of lymphomas. About 22 percent of NHLs are of the follicular type. They are nonaggressive, and the five-year survival rate is 60 percent to 70 percent. However, they tend to transform into an aggressive form that does not respond well to therapy.

About 33 percent of NHLs are of the diffuse type. These tend to be aggressive, fast developing lymphomas that spread outside lymph nodes to the bone, brain and digestive system. About one third of patients with diffuse lymphomas have localized disease and respond well to chemotherapy. Once the disease has spread outside of the lymph nodes, the prognosis is not as good, although many cases are cured with chemotherapy.

Cell type. Most NHLs originate from B-cells, a special type of lymphocyte (white blood cell) that makes antibodies (proteins that help fight infection). The remaining types of lymphoma -- T-cell lymphomas -- originate from the thymus, a gland in the chest where lymphocytes mature into effective immune cells. T-cell lymphomas often behave like leukemia, because the malignant cells spread from the lymph nodes through the blood circulation to the bone marrow.

Genetic and cell surface markers. Non-Hodgkin's lymphomas are also classified according to genetic features (such as chromosomal defects) and the type of molecules found on the cell surface (immunophenotypes).

More on Lymphoma

In the Encyclopedia:

This article was reviewed and updated June 2007.