Correlation between Clinical Outcome and Proliferation Index in Diffuse Large B-Cell Lymphoma

Park, Sung Shin; Huh, Joo ryung; Lee, Seung Sook; Kang, Yun Koo; Heo, Dae Seog; Kim, Chul Woo

Abstract

The diffuse large B-cell lymphoma category of the Revised European American Classification of Lymphoid Neoplasms (REAL) encompasses different morphologic lymphoma subtypes in a single entity, especially the diffuse large cell (DLC) and the immunoblastic (IBL) subtypes by Working Formulation (WF). The aim of this study is to determine the influence of the morphologic subdivision within this category with respect to clinical outcome and proliferative index using Ki-67 immunostainig combined with image analysis. We retrospectively reviewed 74 patients from 1990 to 1996, who were diagnosed with diffuse large B-cell lymphoma. All cases were reclassified according to REAL and Working Formulation (WF), and Ki-67 immunostaining was performed in all the cases. Fifty-eight cases (78.4%) were classified as DLC and 16 cases (21.6%) as IBL, according to WF. Twenty one cases (28.4%) showed nodal involvement and 53 cases (71.6%), extranodal involvement. All cases were found to display a variable degree of nuclear Ki-67 staining. A proliferative index of 50% or higher identified a group of patients (77%) who had poor clinical results. Overall survival was significantly reduced in these patients displaying high Ki-67 associated proliferative index compared to those with a low proliferative index (p=0.007). 5-year survival estimates were 93% in the low proliferative index group and 55% in the high proliferative index group. A multivariate regression analysis incorporating commonly used clinical prognostic factors confirmed the independent effect of proliferation index on survival. Moreover, all of the 16 IBL cases showed Ki-67 positivity of 50% or higher, which correlates with the poor clinical outcome compared to 70.7% of DLC (p=0.014). We conclude that subdivision of the diffuse large B-cell lymphoma category of the REAL classification is necessary in terms of prognostic significance in correlation with Ki-67 proliferative index.