Chapter 105. Malignancies of Lymphoid Cells (Part 4)

The incidence of non-Hodgkins lymphomas and the patterns of expression of the various subtypes differ geographically. T cell lymphomas are more common in Asia than in western countries, while certain subtypes of B cell lymphomas such as follicular lymphoma are more common in western countries. A specific subtype of non-Hodgkins lymphoma known as the angiocentric nasal T/natural killer (NK) cell lymphoma has a striking geographic occurrence, being most frequent in Southern Asia and parts of Latin America. Another subtype of nonHodgkins lymphoma associated with infection by human T cell lymphotropic virus (HTLV) I is seen particularly in southern Japan...
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Chapter 105. Malignancies of Lymphoid Cells (Part 4) Chapter 105. Malignancies of Lymphoid Cells (Part 4) The incidence of non-Hodgkins lymphomas and the patterns of expressionof the various subtypes differ geographically. T cell lymphomas are more commonin Asia than in western countries, while certain subtypes of B cell lymphomassuch as follicular lymphoma are more common in western countries. A specificsubtype of non-Hodgkins lymphoma known as the angiocentric nasal T/naturalkiller (NK) cell lymphoma has a striking geographic occurrence, being mostfrequent in Southern Asia and parts of Latin America. Another subtype of non-Hodgkins lymphoma associated with infection by human T cell lymphotropicvirus (HTLV) I is seen particularly in southern Japan and the Caribbean (Chap.181). A number of environmental factors have been implicated in the occurrenceof non-Hodgkins lymphoma, including infectious agents, chemical exposures, andmedical treatments. Several studies have demonstrated an association betweenexposure to agricultural chemicals and an increased incidence in non-Hodgkinslymphoma. Patients treated for Hodgkins disease can develop non-Hodgkinslymphoma; it is unclear whether this is a consequence of the Hodgkins disease orits treatment. However, a number of non-Hodgkins lymphomas are associatedwith infectious agents (Table 105-4). HTLV-I infects T cells and leads directly tothe development of adult T cell lymphoma (ATL) in a small percentage of infectedpatients. The cumulative lifetime risk of developing lymphoma in an infectedpatient is 2.5%. The virus is transmitted by infected lymphocytes ingested bynursing babies of infected mothers, blood-borne transmission, or sexually. Themedian age of patients with ATL is ~56 years, emphasizing the long latency.HTLV-I is also the cause of tropical spastic paraparesis—a neurologic disorderthat occurs somewhat more frequently than lymphoma and with shorter latencyand usually from transfusion-transmitted virus (Chap. 181). Table 105-4 Infectious Agents Associated with the Development ofLymphoid Malignancies Infectious Agent Lymphoid MalignancyEpstein-Barr virus Burkitts lymphoma Post–organ transplant lymphoma Primary CNS diffuse large B cell lymphoma Hodgkins disease Extranodal NK/T cell lymphoma, nasal typeHTLV-I Adult T cell leukemia/lymphomaHIV Diffuse large B cell lymphoma Burkitts lymphomaHepatitis C virus Lymphoplasmacytic lymphomaHelicobacter pylori Gastric MALT lymphomaHuman herpesvirus 8 Primary effusion lymphoma Multicentric Castlemans disease Note: CNS, central nervous system; HTLV, human T cell lymphotropicvirus; MALT, mucosa-associated lymphoid tissue; NK, natural killer. EBV is associated with the development of Burkitts lymphoma in CentralAfrica and the occurrence of aggressive non-Hodgkins lymphomas inimmunosuppressed patients in western countries. The majority of primary centralnervous system (CNS) lymphomas are associated with EBV. EBV infection isstrongly associated with the occurrence of extranodal nasal T/NK cell lymphomasin Asia and South America. Infection with HIV predisposes to the development ofaggressive, B cell non-Hodgkins lymphoma. This may be through overexpressionof interleukin 6 by infected macrophages. Infection of the stomach by thebacterium Helicobacter pylori induces the development of gastric MALT(mucosa-associated lymphoid tissue) lymphomas. This association is supported byevidence that patients treated with antibiotics to eradicate H. pylori haveregression of their MALT lymphoma. The bacterium does not transformlymphocytes to produce the lymphoma; instead, a vigorous immune response ismade to the bacterium, and the chronic antigenic stimulation leads to theneoplasia. MALT lymphomas of the skin may be related to Borrelia sp. infections,those of the eyes to Chlamydophila psittaci, and those of the small intestine toCampylobacter jejuni. Chronic hepatitis C virus infection has been associated with thedevelopment of lymphoplasmacytic lymphoma. Human herpesvirus 8 is associatedwith primary effusion lymphoma in HIV-infected persons and multicentricCastlemans disease, a diffuse lymphadenopathy associated with systemicsymptoms of fever, malaise, and weight loss. In addition to infectious agents, a number of other diseases or exposuresmay predispose to developing lymphoma (Table 105-5).