Lymphoma is a type of cancer that originates in lymphocytes or, more rarely, of histiocytes. Collectively, these cell types form the reticuloendothelial system and circulate in the vessels of the lymphatic system. There are many types of lymphoma. Lymphomas are part of the broad group of diseases called hematological neoplasms.

In the 19th and 20th centuries the affliction was called Hodgkin's Disease, as it was discovered by Thomas Hodgkin in 1832. Colloquially, lymphoma is broadly categorized as Hodgkin's lymphoma and non-Hodgkin lymphoma (all other types of lymphoma). Scientific classification of the types of lymphoma is more detailed

Prevalence

According to the U.S. National Institutes of Health, lymphomas account for about five percent of all cases of cancer in the United States, and Hodgkin's lymphoma in particular accounts for less than one percent of all cases of cancer in the United States.

Because the lymphatic system is part of the body's immune system, patients with weakened immune system, such as from HIV infection or from certain drugs or medication, also have a higher incidence of lymphoma.

Classification

WHO classification

The WHO Classification is the latest classification of lymphoma, published by the World Health Organization in 2001. It was based upon the "Revised European-American Lymphoma classification" (REAL).

This classification attempts to classify lymphomas by cell type, i.e. the normal cell type that most closely resembles the tumor. They are classified in three large groups: the B cell tumors, the T cell and natural killer cell tumors, Hodgkin lymphoma, and other minor groups: (ICD-Ocodes are provided where available)

Mature B cell neoplasms

DNA-microarray analysis of Burkitt's lymphoma and diffuse large B-cell lymphoma (DLBCL) showing differences in gene expression patterns. Colors indicate levels of expression; green indicates genes that are overexpressed in normal cells compared to lymphoma cells and red indicates genes that are overexpressed in lymphoma cells compared to normal cells.

• • Chronic lymphocytic leukemia/small lymphocytic lymphoma
  • B-cell prolymphocytic leukemia
  • Lymphoplasmacytic lymphoma/Waldenström macroglobulinemia
  • Splenic marginal zone lymphoma
  • Plasma cell neoplasms
    • Plasma cell myeloma
    • Plasmacytoma
    • Monoclonal immunoglobulin deposition diseases
    • Heavy chain diseases
  • Extranodal marginal zone B cell lymphoma (MALT lymphoma)
  • Nodal marginal zone B cell lymphoma
  • Follicular lymphoma
  • Mantle cell lymphoma
  • Diffuse large B cell lymphoma
  • Mediastinal (thymic) large B cell lymphoma
  • Intravascular large B cell lymphoma
  • Primary effusion lymphoma
  • Burkitt lymphoma/leukemia
  • Lymphomatoid granulomatosis

Mature T cell and natural killer (NK) cell neoplasms

• • T cell prolymphocytic leukemia
  • T cell large granular lymphocytic leukemia
  • Aggressive NK cell leukemia
  • Adult T cell leukemia/lymphoma
  • Extranodal NK/T cell lymphoma, nasal type
  • Enteropathy-type T cell lymphoma
  • Hepatosplenic T cell lymphoma
  • Blastic NK cell lymphoma
  • Mycosis fungoides / Sezary syndrome
  • Primary cutaneous CD30-positive T cell lymphoproliferative disorders
    • Primary cutaneous anaplastic large cell lymphoma
    • Lymphomatoid papulosis
  • Angioimmunoblastic T cell lymphoma
  • Peripheral T cell lymphoma, unspecified
  • Anaplastic large cell lymphoma

 Hodgkin Lymphoma

• • Nodular lymphocyte-predominant Hodgkin lymphoma
  • Classical Hodgkin lymphoma
    • Nodular sclerosis
    • Mixed cellularity
    • Lymphocyte-rich
    • Lymphocyte depleted or not depleted

Immunodeficiency-associated lymphoproliferative disorders

• • Associated with a primary immune disorder
  • Associated with the Human Immunodeficiency Virus (HIV)
  • Post-transplant
  • Associated with Methotrexate therapy

 Histiocytic and dendritic cell neoplasms

• Histiocytic sarcoma
• Langerhans cell histiocytosis
• Langerhans cell sarcoma
• Interdigitating dendritic cell sarcoma/tumor
• Follicular dendritic cell sarcoma/tumor
• Dendritic cell sarcoma, unspecified 

 Working formulation

The Working Formulation, published in 1982, is primarily descriptive. It is still occasionally used, but has been superseded by the WHO classification, above.

Low grade

• Malignant Lymphoma, small lymphocytic (chronic lymphocytic leukemia)
• Malignant Lymphoma, follicular, predominantly small cleaved cell
• Malignant Lymphoma, follicular, mixed (small cleaved and large cell)

High grade

• Malignant Lymphoma, large cell, immunoblastic
• Malignant Lymphoma, lymphoblastic
• Malignant Lymphoma, small non-cleaved cells (Burkitt's lymphoma)

Miscellaneous

• Composite
• Mycosis fungoides
• Histiocytic
• Extramedullary plasmacytoma
• Unclassifiable