Frequencies of non-Hodgkin's lymphoma subtypes in Kuwait: comparisons between different ethnic groups

There is a wide variation in the prevalence of various subtypes of non-Hodgkin's lymphoma worldwide. The aim of this study was to determine the relative frequency of different subtypes of non-Hodgkin's lymphoma in Kuwait based on the Revised European-American Lymphoma (REAL) classification. From 1998 to 2006, 738 subjects were included that were registered with non-Hodgkin's lymphoma in the population-based cancer registry at the Kuwait Cancer Control Center. Expert pathologists reviewed histological slides from all subjects. We performed detailed immunohistochemical studies and classified subjects based on the REAL classification. The prevalence of different types of non-Hodgkin's lymphoma was determined based on age, sex, site of disease, and ethnicity. Ethnicity groups comprised Kuwaiti Arabs, non Kuwaiti Arabs, Asians, and others. The prevalence of B- and T-cell lymphomas was 81.8% and 14.2%, respectively. The most common age group was 41-60 years old. The three most common subtypes in Kuwaiti Arabs were diffuse large B-cell lymphoma (46.5%), follicular lymphoma (15.5%), and mycosis fungoides (9.3%). In non-Kuwaiti Arabs, the most common subtypes were diffuse large B-cell lymphoma (48%), B-cell small lymphocytic lymphoma/chronic lymphocytic leukemia (15.8%), and follicular lymphoma (12.7%). Overall, non-Kuwaiti Arabs exhibited the highest prevalence (59%), and 54% of all cases had extranodal presentation. Compared to the Western world, Kuwait had a lower prevalence of follicular lymphoma, a higher prevalence of diffuse large B-cell lymphoma and extranodal presentation, and a high frequency of mycosis fungoides. Compared to other parts of Asia, Kuwait had a lower frequency of peripheral T-cell lymphomas.