Comparing flow cytometry immunophenotypic and immunohistochemical analyses in diagnosis and prognosis of chronic lymphoproliferative disorders: Experience from a Tertiary Care Center

Background: The latest World Health Organization classification incorporates extensive description of immunophenotype of the neoplastic cells while describing chronic lymphoproliferative disorders (CLPDs). The present study was undertaken with an aim to identify and compare the roles of flow cytometry (FCM) and immunohistochemistry (IHC) as modalities of immunophenotyping in the diagnosis of CLPDs. Materials and Methods: Thirty untreated cases of CLPDs were enrolled in the study. Twenty eight cases of B-CLPD were divided into two groups - chronic lymphocytic leukemia (CLL) (21 patients) and non-CLL (7 patients). Peripheral blood/bone marrow aspirate samples were analysed by FCM using various panels of monoclonal antibodies. Immunohistochemical analysis of bone marrow biopsies obtained from these patients was also performed. Results: Panel A of monoclonal antibodies comprising CD5, CD23, CD22, surface membrane immunoglobulin (SmIg), FMC7 and Panel B comprising CD5, CD23, CD22, SmIg, FMC7, CD79b were useful (P < 0.01 and <0.001 respectively) while Panel C comprising CD5, CD23, SmIg, FMC7 and CD79b was not found to be useful in distinguishing CLL from non-CLL (P > 0.05) The concordance rate between FCM and IHC ranged from 80% to 100% for all comparable immunological markers. In all cases of CLPDs, we propose a screening panel comprising 9 markers including CD19, CD5, CD23, FMC7, CD10, CD20, CD3, kappa and lambda, which are important for specifying the lineage (B or T), to differentiate CLL from non-CLL group and for deciding the secondary panel. Conclusion: Scoring system using CD5, CD23, CD22, FMC7, CD79b, and SmIg is useful in differentiating CLL from non-CLL cases. Concordance rate of FCM and IHC in CLPDs is 93.3%. Using a panel comprising CD19, CD5, CD23, FMC7, CD10, CD20, CD3, kappa and lambda, a diagnosis of CLL, mantle cell, and follicular lymphoma, the three most common CLPDs can be made. Secondary panels for diagnosis of hairy cell leukemia and T-cell CLPD should be utilized.