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Chapter 105. Malignancies of Lymphoid Cells (Part 3)

General Aspects of Lymphoid Malignancies Etiology and Epidemiology The relative frequency of the various lymphoid malignancies is shown in Fig. 105-1. Chronic lymphoid leukemia (CLL) is the most prevalent form of leukemia in western countries. It occurs most frequently in older adults and is exceedingly rare in children. In 2007, 15,340 new cases were diagnosed in the United States, but because of the prolonged survival associated with this disorder, the total prevalence is many times higher. CLL is more common in men than in women and more common in whites than in blacks. This is an uncommon malignancy in Asia. The. | Chapter 105. Malignancies of Lymphoid Cells Part 3 General Aspects of Lymphoid Malignancies Etiology and Epidemiology The relative frequency of the various lymphoid malignancies is shown in Fig. 105-1. Chronic lymphoid leukemia CLL is the most prevalent form of leukemia in western countries. It occurs most frequently in older adults and is exceedingly rare in children. In 2007 15 340 new cases were diagnosed in the United States but because of the prolonged survival associated with this disorder the total prevalence is many times higher. CLL is more common in men than in women and more common in whites than in blacks. This is an uncommon malignancy in Asia. The etiologic factors for typical CLL are unknown. Figure 105-1 Relative frequency of lymphoid malignancies In contrast to CLL acute lymphoid leukemias ALLs are predominantly cancers of children and young adults. The L3 or Burkitt s leukemia occurring in children in developing countries seems to be associated with infection by the Epstein-Barr virus EBV in infancy. However the explanation for the etiology of more common subtypes of ALL is much less certain. Childhood ALL occurs more often in higher socioeconomic subgroups. Children with trisomy 21 Down s syndrome have an increased risk for childhood acute lymphoblastic leukemia as well as acute myeloid leukemia. Exposure to high-energy radiation in early childhood increases the risk of developing T cell acute lymphoblastic leukemia. The etiology of ALL in adults is also uncertain. ALL is unusual in middleaged adults but increases in incidence in the elderly. However acute myeloid leukemia is still much more common in older patients. Environmental exposures including certain industrial exposures exposure to agricultural chemicals and smoking might increase the risk of developing ALL as an adult. ALL was diagnosed in 5200 persons and AML in 13 410 persons in the United States in 2007. The preponderance of evidence suggests that Hodgkin s disease is of B cell .