|Non-Hodgkin's Lymphomas (NHL)|
|Classification and external resources|
The non-Hodgkin lymphomas (NHLs) are 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 (CD20), 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 The Working Formulation has been superseded twice.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.
The many different forms of lymphoma likely have different causes. These possible causes and associations with at least some forms of NHL include:
- Infectious agents like Epstein-Barr virus, Human T-cell leukemia virus, Helicobacter pylori, HHV-8, and HIV infection.
- Chemicals, like diphenylhydantoin, dioxin, and phenoxyherbicides.
- Medical treatments like radiation therapy and chemotherapy
- Genetic diseases, like Klinefelter's syndrome, Chédiak-Higashi syndrome, ataxia telangiectasia syndrome
- Autoimmune diseases, like Sjögren’s syndrome, celiac sprue, rheumatoid arthritis, and systemic lupus erythematosus.
Some studies have shown an association between non-Hodgkin lymphoma and exposure to polychlorinated biphenyls (PCBs), a persistent organic pollutant now found throughout the natural environment.However, other similar studies have found no such link. Studies of PCB workers have uniformly shown no statistically significant increased rates of deaths from non-Hodgkin Lymphoma. In 2013, The International Association for Research on Cancer (IARC) determined that the evidence that PCBs cause non-Hodgkin Lymphoma is “limited” and “not consistent.”  Institutions devoted to cancer research and treatment such as the American Cancer Society and the Mayo Clinic do not list PCB exposure as a risk factor for non-Hodgkin Lymphoma.
Non-Hodgkin lymphoma resulted in 210,000 deaths globally in 2010 up from 143,000 in 1990.
Hodgkin lymphoma (HL, Hodgkin disease), described by Thomas Hodgkin in 1832, was the first form of lymphoma described and defined. Other forms were later described and there was a need to classify them. Because Hodgkin lymphoma was much more radiation-sensitive than other forms, its diagnosis was important for oncologists and their patients. Thus, research originally focused on it. The first classification of Hodgkin lymphoma was proposed by Robert J. Luke in 1963.
While consensus was rapidly reached on the classification of Hodgkin lymphoma, there remained a large group of very different diseases requiring further classification. The Rappaport classification, proposed by Henry Rappaport in 1956 and 1966, became the first widely accepted classification of lymphomas other than Hodgkin. Following its publication in 1982, the Working Formulation became the standard classification for this group of diseases. It introduced the term non-Hodgkin lymphoma (NHL) and defined three grades of lymphoma.
However, NHL consists of 16 different conditions that have little in common with each other. They are grouped by their aggressiveness. Less aggressive non-Hodgkin lymphomas are compatible with a long survival while more aggressive non-Hodgkin lymphomas can be rapidly fatal without treatment. Without further narrowing, the label is of limited usefulness for patients or doctors.
Modern usage of term
Nevertheless, the Working Formulation and the NHL category continue to be used by many. To this day, lymphoma statistics are compiled as Hodgkin's vs non-Hodgkin lymphomas by major cancer agencies, including the National Cancer Institute in its SEER program, the Canadian Cancer Society and the IARC.
The Center for Disease Control and Prevention (CDC) included certain types of non-Hodgkin's lymphoma as AIDS-defining cancers in 1987. Immune suppression rather than HIV itself is implicated in the pathogenesis of this malignancy, with a clear correlation between the degree of immune suppression and the risk of developing NHL. Additionally, other retroviruses such as HTLV may be spread by the same mechanisms that spread HIV, leading to an increased rate of co-infection.  HIV-infected patients are at an increased risk for developing both Hodgkin lymphoma and NHL when compared with the general population.
- Lymphoma, for information about all forms of NHL as well as Hodgkin's lymphoma
- Chemotherapy, for information on the standard of care of all forms of non-Hodgkin lymphomas.
- CHOP-R for the most common chemotherapeutic regimen for non-Hodgkin lymphoma.
- American Cancer Society
- American Society of Clinical Oncology)
- Patient information on non-Hodgkin lymphoma from The Lymphoma Association
- non-Hodgkin in Brain MR Scans of Primary Brain Lymphoma
- Lymphoma Association – Specialist UK charity providing free information and support to patients, their families, friends and carers