Lymphoma

The term lymphoma refers to cancers that originate in the body's lymphatic tissues. Lymphatic tissues include the lymph nodes (also called lymph glands), thymus, spleen, tonsils, adenoids, and bone marrow, as well as the channels (called lymphatics or lymph vessels) that connect them. Although many types of cancer eventually spread to parts of the lymphatic system, lymphomas are distinct because they actually originate there.

About 1,700 kids younger than 20 years old are diagnosed with lymphoma each year in the United States. Lymphomas are divided into two broad categories, depending on the appearance of their cancerous (malignant) cells. These are known as Hodgkin disease and non-Hodgkin lymphoma (NHL). Together, they are the third most common type of cancer in children.

Hodgkin Disease

This type of lymphoma is defined by the presence of specific malignant cells, called Reed-Sternberg cells, in the lymph nodes or in some other lymphatic tissue. Hodgkin disease affects about 3 out of every 100,000 Americans, most commonly during early and late adulthood (between ages 15 and 40 and after age 55).

The most common first symptom of Hodgkin disease is a painless enlargement of the lymph nodes (a condition known as swollen glands) located in the neck, above the collarbone, in the underarm area, or in the groin.

If cancer involves the thymus (a gland of the immune system that is larger in children and located in the middle of the chest), pressure from this gland may trigger an unexplained cough, shortness of breath, or problems in blood flow to and from the heart.

About a third of patients have other nonspecific symptoms, including fatigue, poor appetite, itching, or hives. Unexplained fever, night sweats, and weight loss are also common.

Non-Hodgkin Lymphoma (NHL)

There are about 500 new cases of non-Hodgkin lymphoma diagnosed each year in kids in the United States. It may occur at any age during childhood, but is rare before age 3. NHL is slightly more common than Hodgkin disease in kids younger than 15 years old.

In non-Hodgkin lymphoma, there is malignant growth of specific types of lymphocytes (a kind of white blood cell that collects in the lymph nodes). Malignant growth of lymphocytes is also seen in one of the forms of leukemia (acute lymphoblastic leukemia, or ALL), which sometimes makes it difficult to distinguish between lymphoma and leukemia in children. In general, people with lymphoma have no or only minimal bone marrow involvement, whereas those with leukemia have extensive bone marrow involvement.

The development of some types of NHL, such as Burkitt's lymphoma, may have some link to the Epstein-Barr virus (the cause of infectious mononucleosis, or mono). Pieces of viral genetic material have been detected in some cells taken from patients with NHL.

Risk for Childhood Lymphoma

Both Hodgkin disease and NHL tend to occur more often in white males and in people with certain severe immune deficiencies — including people with inherited immune defects, adults with human immunodeficiency virus (HIV) infection, or those who have been treated with immunosuppressive drugs after organ transplants.