The non-Hodgkin lymphomas (NHLs) are a diverse group of blood cancers that include any kind of lymphoma except Hodgkin's lymphomas. Types of NHL vary significantly in their severity, from indolent to very aggressive.
Lymphomas are types of cancer derived from lymphocytes, a type of white blood cell. Lymphomas are treated by combinations of chemotherapy, monoclonal antibodies, immunotherapy, radiation, and hematopoietic stem cell transplantation.
Non-Hodgkin lymphomas were classified according to the 1982 Working Formulation which recognizes 16 types. The Working Formulation is now considered obsolete, and the classification is commonly used primarily for statistical comparisons with previous decades. The Working Formulation has been superseded twice.
The latest lymphoma classification, the 2008 WHO classification, largely abandoned the "Hodgkin" vs. "Non-Hodgkin" grouping. Instead, it lists over 80 different forms of lymphomas in four broad groups.
A number of peer-reviewed health studies have shown a causal link between non-Hodgkin lymphoma and exposure to polychlorinated biphenyls (PCBs), a persistent organic pollutant now found throughout the natural environment.