**2. Non-Hodgkin Lymphoma**

Non-Hodgkin lymphoma is a heterogeneous group of B-cell and T-cell neoplasm that arise primarily in the lymph nodes with varied clinical and biologic feature. Current classification system include the Revised European-American Lymphoma (REAL) classification and the World Health Organization (WHO) classification of hematopoietic and lymphoid neoplasms (Alexander, et al., 2007). The distribution of NHL types varies internationally (Anderson, Armitage, & Weisenburger, 1998). Epidemiological investigation of the NHL and its etiology may result in a better understanding and hence prevention.
