Use of the World Health Organization (WHO) classification of non-Hodgkin's lymphoma in Mumbai, India: a review of 200 consecutive cases by a panel of five expert hematopathologists.

This study aims to answer the question whether the World Health Organization (WHO) classification of non-Hodgkin's lymphoma (NHL) can be practised to international standards at the Lymphoma Registry (LR) established at the Tata Memorial Hospital, Mumbai, India. Furthermore, the study aims to identify differences in the distribution of NHL subtypes at this LR (likely to be representative of India) as compared to the rest of the world. A panel of 5 expert hematopathologists from the NHL Classification Project reviewed 200 consecutive NHL cases at the LR in January of 2001. These cases were accrued during August and September, 2000. On all cases, hematoxylin and eosin stains and appropriate immunostains were available for review. The diagnosis made by the host pathologist at the LR (KNN) and the initial diagnosis made by each of the expert hematopathologists was compared with the consensus diagnosis. A consensus diagnosis was made by the 5 experts in 197 cases. The agreement of the host pathologist with the consensus diagnosis was 82% and the agreement of the individual experts with the consensus diagnosis varied from 76-88% (mean 82%). According to the consensus diagnosis, 80% of NHLs were of B-cell type, 18% were of T-cell type, and the immunophenotype could not be determined in the remaining 2% of cases. In conclusion, the WHO classification of NHL was properly utilized at the Lymphoma Registry, Mumbai, India, and geographic differences were noted in the distribution of NHL subtypes at the LR as compared to the rest of the world. Precursor T lymphoblastic leukemia/lymphoma was more common in India (7%) than the rest of the world (1-4%), and indolent B-cell NHLs (29%) were less common than in the West. As compared to China and Japan, peripheral T-cell lymphoma (4.6%), extranodal NK/T cell lymphoma, nasal type (0.5%) and extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT-lymphoma) (2.6%) were less common, but follicular lymphoma (15%) and chronic lymphocytic leukemia/small lymphocytic lymphoma (5%) were more common. This suggests that the distribution of the B-cell and T-cell lymphomas in the Indian population, except for lymphoblastic lymphoma, lies in between the Western world (mainly Caucasian) and the Orientals.