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Lymphoma

Background

“Lymphoma" can refer to one of numerous different lymphoma subtypes (Morton 2013; Clarke 2006). The most common subtypes of NHL include diffuse large B-cell lymphoma (DLBCL), which makes up about 30% of all NHL in the United States, and follicular lymphoma, which accounts for roughly 20% of all NHL (Leukemia & Lymphoma Society 2011a).

Lymphomas are cancers of white blood cells (lymphocytes) within the lymphatic system. Lymphocytes can be B lymphocytes (B cells), T lymphocytes (T cells), or natural killer (NK) cells. B cells fight infection by producing antibodies whereas some T cells directly kill virus-infected or cancer cells; NK cells attack cells infected by a virus without the need for antibodies. About 85% of NHLs are of B cell origin (Leukemia & Lymphoma Society 2011a).

Lymphomas can arise as a consequence of a genetic mutation, eventually leading to the formation of a mass of malignant cells (tumor), often in the lymph nodes and sometimes in other body parts. The specific cells affected may be B cells, T cells, and sometimes natural killer (NK) cells (Kobrinsky 2012; Leukemia & Lymphoma Society 2011a; Leukemia & Lymphoma Society 2011b).

HL is usually differentiated from NHL by the presence of characteristic large cells called Reed-Sternberg cells. These cells typically emerge from B cells. Reed-Sternberg cells are the hallmark of HL; however, rarely, these cells may sometimes be seen in other diseases, such as NHL, as well as infectious mononucleosis (Küppers 2005; Thomas 2004; Khan 1993).

There are five types of HL, four of which – nodular sclerosis, mixed cellularity, lymphocyte depleted, and lymphocyte rich – are known as classic HL. The fifth type is called nodular lymphocyte predominant Hodgkin disease; it presents with peculiar features and is treated differently than the classic types (Lash 2013; Townsend 2012).

There are many types of NHL, several of which are outlined in the following table.

Non-Hodgkin lymphoma subtypes, relative frequencies (%), and characteristics (Abramson 2006; Marcucci 2011; Gajra 2013; Al-Humood 2011; Visco 2006; Leukemia & Lymphoma Society 2011a; Schöllkopf 2008; Armitage 1989; LRF 2012)

NHL types (relative frequencies by %)

Characteristics

A) B-cell lymphoma (80-90% of NHL)

Involves B cells but also includes T cell rich large B-cell lymphoma; associated with hepatitis B and C virus.

Diffuse large B-cell lymphoma (DLBCL) (31%)

Lymphoma can be either primary lymph node disease or at extranodal (outside the lymph node) sites; associated with hepatitis C virus 

Follicular lymphoma (22%)

Lymphoma cells have a follicular growth pattern (ie, the cells tend to grow in a circular pattern in lymph nodes)

MALT lymphoma (mucosa-associated lymphoid tissue) (7.5%)

Extranodal marginal zone lymphoma of mucosa-associated lymphatic tissue; gastric (stomach) in origin but can occur in other areas of the body; associated with Helicobacter pylori (H. pylori) infection

Mantle cell lymphoma (6%)

Originates in the mantle zone of the lymph node; it is usually widespread at the time of diagnosis; associated with Borrelia burgdorferi

Burkitt’s Lymphoma (2.5%)

Rare in adults but accounts for 30% of childhood NHL in the United States. EBV is associated with the development of Burkitt's lymphoma.

B) T- and NK-cell lymphomas (~12% of all NHL)

Several subtypes exist, including Sézary syndrome and mycosis fungoides (cutaneous T-cell lymphoma)

Mature T-cell lymphoma (7.6%)

Lymphoma cells have characteristics similar to T-cells; linked to human T-cell lymphotropic virus type 1; it is the most frequent T-cell lymphoma in the United States

Cutaneous T-cell lymphoma (2-3%)

This type of lymphoma includes mycosis fungoides and Sezary syndrome, and it may wax and wane over the course of several years, a characteristic that makes its diagnosis difficult

C) Immunodeficiency-associated lymphoproliferative disorders (relatively rare)

AIDS-associated lymphoma; posttransplantation lymphoproliferative disorder; and lymphoma associated with a primary immune disorder

The parenthetical percentages are approximate but provide perspective of the relative distribution of NHL subtypes.