A risk factor is anything that might affect a person's chance of getting cancer. Different cancers have different risk factors. But risk factors don't tell us everything. Having a risk factor, or even several risk factors, does not mean that you will get the disease. And many people who get the disease may not have had any known risk factors. Even if a person has a risk factor and develops cancer, it is often very hard to know how much that risk factor may have contributed to the cancer.

Lifestyle-related risk factors such as diet, body weight, physical activity, and tobacco use play a major role in many adult cancers. But these factors take many years to influence cancer risk, and they are not thought to be a significant source of childhood cancers.

Most children with non-Hodgkin lymphoma do not have any known risk factors for this disease. But researchers have found some factors that may put children at increased risk.

Age, gender, and race

Non-Hodgkin lymphoma is rare in children in general, but it is more common in older children than in younger ones. It is also more common in boys than in girls and in white children than in black children.

Weakened immune systems

Several types of immune system problems have been linked with a higher risk of non-Hodgkin lymphoma in children.

Congenital (present at birth) immune deficiency syndromes

Some genetic (inherited) syndromes can cause children to be born with an abnormal or deficient immune system. Along with an increased risk of serious infections, these children also have a higher risk of developing non-Hodgkin lymphoma. These syndromes include:

• Wiskott-Aldrich syndrome
• severe combined immunodeficiency syndrome (SCID)
• ataxia-telangiectasia
• common variable immunodeficiency
• Bloom syndrome
• X-linked lymphoproliferative syndrome

Although these congenital (present at birth) immune deficiency diseases can be passed on to children, non-Hodgkin lymphoma survivors who do not have these inherited diseases do not pass on an increased risk of non-Hodgkin lymphoma to their children.

Organ transplants

Children who have received organ transplants are treated with drugs that weaken their immune system to prevent it from attacking the new organs. These children have an increased risk of developing non-Hodgkin lymphoma that is almost always caused by Epstein-Barr virus infection. The risk depends on which drugs and what doses are used.

HIV/AIDS

Infection with human immunodeficiency virus (HIV), also known as the AIDS virus, is a cause of immune system deficiency in children and adults. HIV infection is a risk factor for developing non-Hodgkin lymphoma. Children with non-Hodgkin lymphoma may be tested for HIV infection.

Radiation exposure

Radiation exposure may be a minor risk factor in childhood non-Hodgkin lymphoma.

Survivors of atomic bombs and nuclear reactor accidents have an increased risk of developing several types of cancer. Although leukemia and thyroid cancers are the most common, there is a slightly increased risk of non-Hodgkin lymphoma as well.

Patients treated with radiation therapy for other cancers have a slightly increased risk of developing non-Hodgkin lymphoma later in life. However, it usually takes many years for this to happen, so these secondary cases of non-Hodgkin lymphoma are more common in adults than children.

Epstein-Barr virus infection

In areas of Africa where Burkitt lymphoma is common, chronic infection with both malaria and the Epstein-Barr virus (EBV) is an important risk factor. EBV has been linked with as many as 90% of Burkitt lymphomas in Africa. In the United States, EBV has been linked with about 15% of Burkitt lymphomas. Although most Americans have been infected with EBV by the time they are adults, the infection seems to occur later in life than in Africa, which may help explain the difference in numbers. Another factor may be that in certain parts of Africa, children's immune systems also have to deal with other infections, such as malaria, which may make them less able to clear EBV from the body. In American teenagers and young adults, EBV infection is the cause of infectious mononucleosis, sometimes known simply as mono.

Exactly how EBV is linked to Burkitt lymphoma is not completely understood, but it seems to have to do with the ability of the virus to infect and alter B lymphocytes. (For more information, see the section "Do we know what causes non-Hodgkin lymphoma in children?")

It is important to remember that most children with non-Hodgkin lymphoma have no known risk factors. There is nothing these children or their parents could have done to prevent this cancer.

Last Medical Review: 07/08/2009
Last Revised: 07/08/2009