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Harvard Medical School

Lymphoma (Hodgkin Disease and Non-Hodgkin Lymphoma)

What Is It?

The lymphatic system is part of the body's defense against infections. The system is a network of vessels throughout the body that collect invading organisms, such as viruses, and abnormal cells. The invaders are moved into lymph nodes where they are destroyed by white blood cells, including cells called lymphocytes. In general, there are two major types of lymphocytes, so-called T and B cells. B Lymphocytes are responsible for the body's manufacturing of chemicals called antibodies, while T lymphocytes are involved in the body's fighting off infections and cancers with specially immunized cells.

Lymphoma is a cancer of the lymphocytes, which means these cells grow abnormally and out of control. Lymphoma usually begins in a lymph node, but it also can begin in the stomach, intestines, skin or any other organ, since lymphocytes are found in all of these organs. The two main types of lymphoma are Hodgkin disease and non-Hodgkin lymphoma. Over the past decade, there have been important advances in understanding the derivation of lymphocytes that come from different areas of the lymph node (e.g., the inside portion, outside portion) as well as lymphocytes that populate specific organs in the body. Consequently, many lymphomas of the non-Hodgkin variety are further subclassified and this information is taken into account when a diagnosis is made.

Hodgkin DiseaseIn Hodgkin disease, the abnormal cells are called the Reed-Sternberg cells. This type of cancer can spread throughout the lymphatic system, affecting any organ or lymph tissue in the body. Hodgkin disease usually affects people in their late 20s or older than 50. Males get the disease more often than females, and whites are affected more often than people of other races. The disorder strikes about 5 in every 100,000 people.

Non-Hodgkin LymphomaMost lymphoma is non-Hodgkin lymphoma. In adults, non-Hodgkin lymphoma affects males more than females and often occurs between the ages of 60 and 70. Whites are affected more often than people of other races. The disorder affects about 16 in every 100,000 people — or about 45,000 people in the United States.

This cancer has become more common. This may be related to the rise in the number of people who have suppressed immune systems, such as people infected with human immunodeficiency virus (HIV) and people who have undergone an organ transplant that requires long-term treatment with drugs that alter the immune system.

Different types of lymphoma occur in different age groups.

• In adulthood — Adult non-Hodgkin lymphoma is classified by the size, type and distribution of cancer cells in the lymph nodes. The three types are low grade (slower growing), intermediate grade and high grade (aggressive).

  • Low-grade lymphomas include small-lymphocytic lymphoma, follicular small-cleaved-cell lymphoma and follicular mixed-cell lymphoma.

  • Intermediate-grade lymphomas include follicular large-cell lymphoma, diffuse small-cleaved-cell lymphoma, diffuse mixed lymphoma and diffuse large-cell lymphoma.

  • High-grade lymphomas include immunoblastic lymphoma, lymphoblastic lymphoma and small noncleaved (Burkitt's and non-Burkitt's) lymphoma.

  • There are also more refined molecular classifications of these types of non-Hodgkin lymphoma based upon specific chemicals and genes of the cell.

• In childhood — Childhood non-Hodgkin lymphomas include lymphoblastic lymphoma, large-cell lymphoma and small-noncleaved-cell lymphoma (including Burkitt's and non-Burkitt's lymphomas). Note that high-grade (aggressive) non-Hodgkin lymphomas usually affect children and young adults.

Several factors may contribute to the development of lymphoma:

• Environmental factors — Recent studies show a possible link between lymphoma and exposure to certain chemicals, herbicides and insecticides. Further study is needed.

• Genetic factors — Studies indicate that patients with certain genetic (inherited) immunodeficiency disorders, such as Wiskott-Aldrich syndrome, may have an increased risk of developing lymphoma.

• Viral infections — Research suggests links between lymphoma and certain viruses, such as the Epstein-Barr virus and HIV. For example, one study found that Burkitt's disease was related to Epstein-Barr virus in nearly all cases in Africa and in 15% of U.S. cases. Patients infected with HIV, especially those with AIDS, also are more likely to get both Hodgkin and non-Hodgkin lymphoma.