Lymphoma is a cancer that affects a type of white blood cell called a lymphocyte. Lymphocytes are immune cells that normally protect us from illness.
Non-Hodgkin lymphomas (NHL) are classified according to the World Health Organization (WHO) classification system. The WHO classification system is an updated version of the Revised European American Lymphoma (REAL) classification system. The different types of lymphoma are determined by the type of lymphocyte that has become cancerous and the stage in its development at which it became cancerous. The WHO classification system classifies NHL according to whether they are B- or T–cell lymphomas. NK-cell lymphomas are included in the T-cell group.
The B- and T–cell lymphomas are further classified into 2 basic types based on their stage of development (maturation):
Lymphomas and lymphoid leukemias are both included in the WHO classification for lymphomas because they both start in the same type of cell – the lymphocyte. They are basically the same disease and only differ in how and where they present:
About 85% of cases of NHL are B-cell lymphomas. The remaining 15% are T-cell and NK-cell lymphomas. Some of the more common subtypes of NHL include:
The WHO classifies non-Hodgkin lymphomas according to the appearance of the lymphoma cells, genetic or chromosome characteristics of the cells and the presence of certain markers on the surface of the cells. There are over 30 subtypes of NHL.
Precursor B-cell lymphoma
precursor B-lymphoblastic leukemia or lymphoma
Mature B-cell lymphoma
AIDS-related lymphoma, primary central nervous system (CNS) lymphoma and post-transplant lymphoproliferative disorder are other types of non-Hodgkin lymphomas that are mostly B-cell tumours.
Hairy cell leukemia and plasmacytoma (plasma cell myeloma or multiple myeloma) are also B-cell cancers, but are addressed elsewhere. For more information, go to hairy cell leukemia and multiple myeloma.
Precursor T-cell lymphoma
precursor T-lymphoblastic leukemia or lymphoma
Mature T- and NK–cell lymphoma
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