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The lymphomas are a heterogeneous group of malignancies that originate in a single lymphocyte that has undergone transforming mutations that confer on it a growth and survival advantage in comparison to its normal cellular counterparts. The neoplasm usually originates in a lymph node, or lymphatic tissue in other sites (extranodal lymphoma), and can be localized or widespread at the time of diagnosis. Men are usually affected more frequently than women and the disease increases logarithmically with age. Classification systems have considered the likely lymphoid progenitor that corresponds to the phenotype (immunotype) and genotype of the malignant cells in the clone. By identifying whether the involved lymphocytes have (1) surface features of B, T , or natural killer (NK) cells, (2) the complete pattern of the CD antigens on their surface, the appearance of the histopathology in the tissue section, specific cytogenetic findings, especially translocations (e.g., t[11;14]), and immunocytochemical markers (e.g., cyclin D1), the specific tissue location (e.g., mucosa-associated lymphatic tissue), the unique pathologic diagnosis can usually be made. Although most lymphomas are without an evident cause, human T-cell leukemia/lymphoma virus I (HTLV-1), Epstein-Barr virus, hepatitis C virus, and human herpes virus-8 infections, as well as infections with the bacteria Helicobacter pylori and, perhaps, Chlamydophila psittaci either are established as causal (e.g., HTLV-1) or have very strong associations with lymphoma incidence (hepatitic C virus), suggesting their role in causation. HIV is permissive in that by inducing severe immunodeficiency it sets the stage for a Epstein-Barr virus-induced or human herpes virus-8–induced lymphoma. These relationships may vary by geographical area. Several occupational and industrial exposures are suspected of being related to lymphoma incidence, for example, organochlorines, phenoxyacid herbicides, and others, but these associations have not been established with scientific certainty. At present, the estimated attributable risk of lymphoma from all suspected exogenous factors together is relatively small in proportion to the number of annual cases, leaving most cases without an apparent cause. There are wide discrepancies in the incidence of specific lymphoma subtypes in different geographic regions (e.g., follicular lymphoma very common in the United States and very uncommon in East Asia). Primary extranodal lymphoma may involve virtually any tissue or organ. Depending on the site, important functional abnormalities may ensue (e.g., bilateral adrenal gland replacement and hypoadrenocorticism, hypothalamic-pituitary involvement and diabetes insipidus). Some combination of surgical excision, radiotherapy, and multidrug chemotherapy and lymphocyte-specific monoclonal antibody therapy is used in treatment depending on the site and histopathology.

Acronyms and Abbreviations

Abbreviations and acronyms used in this chapter include: MALT lymphoma, marginal zone B-cell lymphoma of mucosa-associated lymphatic tissue; NK, natural killer; REAL, revised European-American classification of lymphoid neoplasm; SEER, Surveillance, Epidemiology, and End Results; WHO, World Health Organization.

Lymphomas are a heterogeneous group of malignancies of B cells, T cells, and, rarely, natural killer (NK) cells that usually originate in the lymph nodes, but which may originate in any organ of the body. Lymphoma previously was referred to as lymphosarcoma...

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