Non-Hodgkin lymphoma (also called non-Hodgkin's lymphoma, NHL, or just lymphoma) is a group of cancers that start in lymphoid tissue (also called lymph or lymphatic tissue). Other types of cancer (lung or colon cancers, for example) can start in other organs and then spread to lymphoid tissue. But these cancers are not lymphomas. Lymphomas start in the lymphoid tissue and can then spread to other organs. There are two main types of lymphomas: Hodgkin lymphoma, and all other types of lymphoma called non-Hodgkin lymphomas. The cells of these two types of cancer look different under a microscope, but in some cases, special laboratory tests may be needed to tell them apart.
Non-Hodgkin Lymphoma and the Environment
The causes of Non-Hodgkin lymphomas are mostly unknown. Specific viruses, immune deficiency, and specific autoimmune conditions have been implicated in increased risk. However, some environmental factors, including exposures to pesticides and solvents, are also being investigated.
Exposure and Risk
Most patients with Non-Hodgkin lymphomas have no known risk factors; however, a few risk factors that may make a person more likely to get Non-Hodgkin lymphomas have been determined. These factors include:
Increasing age is a strong risk factor for this disease; most cases occur in people aged 60 years or older.
- Exposure to Certain Chemicals
Some studies have suggested that chemicals such as benzene and certain herbicides and insecticides may be linked with an increased risk for Non-Hodgkin lymphomas. More research is needed to determine the validity of these studies.
- Treatment with Chemotherapy Drugs
Not clear whether this increased risk is an effect of the treatment or the inherent course of disease.
Some chemotherapy drugs used to treat cancers can increase the risk for leukemia or Non-Hodgkin lymphomas many years later. For example, patients who have been treated for Hodgkin disease have an increased risk for Non-Hodgkin lymphomas later in life.
- Radiation Exposure
Survivors of atomic bombs or nuclear reactor accidents have a higher risk for many kinds of cancer, including Non-Hodgkin lymphomas.
Persons treated with radiation therapy for cancers also have a slightly higher risk for Non-Hodgkin lymphomas later in life.
Risk is greater if both radiation and chemotherapy were used during the cancer treatment.
- Weakened Immune Systems
People with weakened immune systems are at increased risk for Non-Hodgkin lymphomas. For example, patients who receive organ transplants (kidney, heart, liver) are treated with drugs that suppress their immune system to prevent it from attacking the new organ. The exact risk depends on the type and dosage of drugs that were used. .
Sometimes children are born with a dysfunctional immune system. These children have a higher risk for developing Non-Hodgkin lymphomas in childhood or as young adults.
- Autoimmune Diseases
In these diseases, the immune system is dysfunctional and responds to the person's own body as if it was a foreign substance and tries to destroy it.
Some autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus (SLE), have been linked to an increased risk for Non-Hodgkin lymphomas.
- Certain Infections
Epstein-Barr virus (mainly in patients infected with HIV)
Helicobacter pylori (a type of bacteria that causes stomach ulcers)
HIV infection (also known as the AIDS virus)
HTLV-1 (a virus in the same family as HIV)
- Body Weight and Diet
Being very overweight (obese) might increase the risk for Non-Hodgkin lymphomas.
Some studies have suggested that a diet high in vegetables may lower the risk for Non-Hodgkin lymphomas; more research is needed to confirm this.
Reduce Your Risk
Most people who have Non-Hodgkin lymphomas have no known risk factors, and the cause of their cancer is unknown. The best way to prevent this cancer is to reduce known risk factors, such as reducing the spread of HIV, which causes AIDS. HIV is spread among adults usually through sex or sharing contaminated needles by IV drug users. Treating AIDS with new anti-HIV drugs appears to reduce the risk for Non-Hodgkin lymphomas.
By exploring the relationship between Helicobacter pylori and lymphoma, some methods to prevent Non-Hodgkin lymphomas may be discovered. More research is needed to discover these possibilities.
Doctors are also exploring cancer treatment and organ transplant methods that reduce the risk of lymphoma. However, in the case of life-threatening diseases, the risk of acquiring lymphoma later must be balanced against the immediate need to treat the critical disease.