large b cell lymphoma | Non-Hodgkin lymphomas: Risk Factors The exact causes of the occurrence of non-Hodgkin's lymphoma are not known.

Non-Hodgkin lymphomas: Risk Factors
The exact causes of the occurrence of non-Hodgkin's lymphoma are not known. 



The occurrence of non-Hodgkin's lymphoma may be favoured by a combination of risk factors, many of which have been identified in recent years.

The vast majority of them, however, have only a small weight, that is, the risk is barely more important than for a person who does not have a risk factor. Presenting a risk factor does not imply the development of lymphoma in the long term.

Family Risk Factors
It is known that an individual with a family member who has been affected by non-Hodgkin's lymphoma has a slightly greater risk of developing non-Hodgkin's lymphoma than an individual with no family history.

Moreover, for some non-Hodgkin lymphomas, such as diffuse lymphoma with large B cells, the more the disease affects members in the family, the higher the risk. The role of family history in the occurrence of non-Hodgkin lymphomas has led scientists to investigate possible genetic factors. To do this, researchers compare the genes of the patients with those of non-Hodgkin's lymphoma and seek to determine if the genes of the patients present alterations. Some genes involved in immunity are thus being validated as factors likely to increase the risk of non-Hodgkin's lymphoma. However, doctors do not carry out an organized screening in the family.

Risk factors related to immunity
Immunosuppression is a major risk factor. Different situations are at the root of a decrease in immune defenses: autoimmune diseases such as disseminated lupus erythematosus, the long-term immunosuppressive treatments indispensable during organ transplant or even Congenital immune deficiency (dysfunction of abilities to fight infections and inflammations).

Some viral infections may also increase the risk of developing non-Hodgkin's lymphoma. This is the case of HIV infection, responsible for AIDS, which increases the risk of aggressive lymphoma. Epstein-Barr virus or hepatitis C virus also promotes the occurrence of non-Hodgkin lymphomas.

Finally, infections prolonged by bacteria are also involved: some forms of lymphomas that affect the stomach are associated with the presence of the bacterium Helicobacter pylori. Thus, a simple antibiotic treatment helps to treat the disease for certain lymphomas.

Epstein Barr virus (EBV)
EBV belongs to the large family of herpes viruses; It is the origin of mononucleosis. It infects the B lymphocytes from which it activates the growth genes. In the vast majority of cases this leads to a simple swelling of the lymph nodes. But in some cases, years after infection, infected cells can turn into cancerous cells. Three types of lymphoma are related to EBV infection: Non-Hodgkin's lymphoma linked to an organ transplant or AIDS-related immunosuppression, Burkitt's lymphoma, which is part of non-Hodgkin lymphomas, and Hodgkin's lymphoma. Burkitt's lymphoma is a cancer that affects children in some African countries. As for Hodgkin's lymphoma, it is estimated that 40% of people living in a western country who suffer from this disease are also infected with EBV. The molecular mechanism has not yet been identified, but researchers are trying to understand how EBV can transform a healthy lymphocyte into a cancerous lymphocyte. Like all the risk factors listed above, EBV infection alone cannot explain the occurrence of lymphoma.

Environmental factors
The appearance of non-Hodgkin's lymphoma is also related to the use of toxic products, such as dioxins produced by incinerators. Solvents and inks expose workers in print shops to a risk of non-Hodgkin's lymphoma. In June 2013, INSERM5 's expertise concluded that there was a strong presumption of a link between pesticide exposure and non-Hodgkin lymphomas for occupational populations in the agricultural sector.

This dossier was carried out with the assistance of Dr Philippe Solal-Céligny, oncologist Hematologist, medical director and director of clinical research of the Institute of Western Cancer (ICO) (Nantes-Angers) and Chairman of the Scientific Council Of the Association France Lymphoma Hope.