Background: Geographic variations in the histopathologic pattern of non-Hodgkin's lymphoma (NHL) are well documented. Insight into this epidemiologic data might shed light on the underlying etiology. Currently, there is a paucity of information regarding the pattern of NHL occurring in Thailand and Southeast Asia. The current nationwide study was undertaken to obtain a clearer definition of the disease among Thais and to compare this information with data from other Asian and Western countries.
Methods: A retrospective analysis of histopathologic subtypes and clinical features was conducted in 1391 patients (age > or = 15 years) with NHL, who were treated at 6 major medical centers in 4 representative areas of Thailand. One hundred and thirty unselected cases were immunohistochemically studied. The reports from other countries used for comparison were identified through a computerized search on MEDLINE.
Results: Of the total cases studied, follicular lymphomas constituted 3.8% and diffuse lymphomas 91.4%. The frequency of low and intermediate grade (including large cell immunoblastic, using the Working Formulation) were 12.8% and 72.9%, respectively. The most common histologic subtype was the diffuse large cell and large cell immunoblastic entity, which constituted 39.9% of the cases studied. The rate of small lymphocytic and diffuse small cleaved subtypes were higher than in the United States. Of the 130 cases studied, T-cell lymphoma comprised 16.1%, which was much less than in Japan, China, or Taiwan.
Conclusions: The histopathologic pattern of NHL in Thailand was characterized by the features noted for Asia, i.e., a low rate of the follicular entity and a preponderance of the diffuse aggressive subtypes. In addition, the frequency of the small lymphocytic and diffuse small cleaved subtypes were increased compared with the Western population and the rate of T-cell lymphoma appeared to be less than in Far East Asia.