The pattern of Epstein-Barr virus infections in lymphoma of Malaysians

Previous studies of the pattern of lymphoma in multi-ethnic West Malaysian population have shown a high frequency of EBV association in childhood Hodgkin's lymphoma (HL) and adult NK/T-cell lymphomas, with a predilection of the former in Indians and the latter in Chinese. This thesis aims to expand knowledge of the EBV association pattern in childhood non-Hodgkin's lymphoma (NHL), Burkitt's lymphoma (BL), ethnic predilection and virus subtype pattern for Malaysian patients. The childhood NHL pattern is similar to other parts of the world. BL, lymphoblastic lymphoma and diffuse large cell lymphoma (predominantly CD30- positive, ALK-positive anaplastic large cell type) form the 3 major groups of the disease. The difference in subtype composition results in different overall EBV association rates for T- and B-cell lymphomas when compared to the adults, being 3x higher in the B-cell lymphomas in children and the reverse for T-cell lymphomas. The frequency of BL in West Malaysian children is not higher and in the malaria endemic state of Sabah the pattern of lymphoma is similar to other Asian series. The low incidence of jaw presentation, more common abdominal and lymph node disease, and EBV association rate of 33% are features of sporadic BL. Using a sensitive nested-PCR test on 38 lymphomas, 14 nasopharyngeal carcinomas, 12 reactive lymph nodes and tonsils, only EBV type A was identified. This was irrespective of the anatomical sites of the biopsy material, age group, sex and ethnicity of the patients. EBV was identified in sequential biopsies of EBV associated lymphomas, and continued to be absent in non-EBV associated cases, supporting the probable pathogenetic role of the virus. In conclusion, EBV type A is the prevalent subtype of virus present in Malaysian patients. East-West differences in lymphoma pattern are less distinct in children. BL is of the sporadic type and the predilection of EBV associated T- NHL to Chinese is again reflected in Malaysian children, supporting the notion that ethnic Chinese are at risk of developing EBV-associated cancers.