Causes and Risk Factors
Doctors don't know why some cells become non-Hodgkin lymphoma (NHL) cells and others don't. For most people who have NHL, there are no obvious reasons why they developed the disease.
Researchers have identified certain potential risk factors that can increase the chance of developing NHL. They've found that people who live and work in farming communities tend to have a higher incidence of NHL. Studies suggest there might be a link to some ingredients in herbicides and pesticides.
Researchers also think NHL may be associated with exposure to certain bacteria and viruses, especially those that suppress the immune system, such as:
- human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS)
- Epstein-Barr virus
- human T-lymphocytotropic virus (HTLV)
- Helicobacter pylori (the bacteria that causes stomach ulcers)
You can't catch NHL from someone else. Experts have found that about a dozen inherited - but rare - syndromes may increase NHL risk.
How Does NHL Develop?
NHL usually starts with an abnormal change in a white cell in a lymph node or lymphoid tissue called a lymphocyte. It can start in one of three major types of lymphocytes:
- B lymphocytes (B cells), which produce antibodies to help combat infections
- T lymphocytes (T cells), which have several functions, including helping B lymphocytes make antibodies
- natural killer (NK) cells, which attack virus-infected cells or tumor cells
About 85 percent of NHL cases start in the B cells. Your doctor plans your treatment according to the type of cell your NHL developed in.
The abnormal lymphocyte grows out of control and produces more abnormal cells like it. These abnormal lymphocytes (lymphoma cells) accumulate and form masses (tumors). If NHL isn't treated, the cancerous cells crowd out normal white cells, and the immune system can't guard against infection effectively.
NHL that develops in or spreads to other areas of the body where lymphoid tissue is found, such as the spleen, digestive tract and bone marrow, is called primary extranodal lymphoma.
NHL is classified into more than 30 different subtypes. Doctors classify the NHL subtypes into categories that describe how rapidly or slowly the disease is progressing: aggressive NHL and indolent (slow-growing) NHL.