Objective: To explore the immunophenotypic characteristics of CD5⁺ B cell lymphoproliferative disorders (B-LPD) of Chinese patients.

Methods: Immunophenotyping of bone marrow and (or) of peripheral blood was performed in patients with B-LPD by four color multiparameter flow cytometry analysis using a panel of monoclonal antibodies, and the patients clinical data were retrospectively analyzed. The difference in immunophenotypes and the related clinical features were retrospectively analyzed. Fluorescence in situ hybridization (FISH) for t(11;14) detection was applied to diagnose or exclude mantle cell lymphoma.

Results: (1)A total 260 CD5⁺ B-LPD patients were enrolled in this study, including 186 chronic lymphocytic leukemia (CLL), 40 mantle cell lymphoma (MCL), other B-LPD including 5 splenic marginal zone lymphoma (SMZL), 2 B-cell prolymphocytic leukemia (B-PLL), 3 hairy cell leukemia (HCL). The other 26 cases (10%)were not classified and defined as unclassified B-LPD (BLPD-U). MCL patients were all positive for t(11;14) detected by FISH, while all the BLPD-U patients were negative for t(11;14). (2) All patients expressed CD19, CD20 and CD5. According to the immunophenotypic score system, 186 CLL patients scored 4-5, 99.5% of patients with CD23⁺, 11.3% with sIgM⁺, 10.2% with FMC7⁺, 44.1% with CD22⁺ and 51.1% with CD11c⁺. MCL patients scored 2-3, with 50% expressing CD23 and sIgM, 81.6% expressing FMC7, 92.1% expressing CD22 and 5.3% expressing CD11c. In aspect of BLPD-U and other B-LPD, the expression of CD23, sIgM, FMC7, CD22 and CD11c were 73.1% and 50%, 34.6% and 50%, 88.5% and 100%, 92.3% and 90%, 69.2% and 70%, respectively. (3)In comparison of CLL with MCL, there was a significant difference in the expression of CD23, sIgM, FMC7, CD22 and CD11c between the two groups (P<0.01). Between MCL and BLPD-U, similar expression type of CD23, sIgM, FMC7 and CD22 was found except CD11c, which was highly expressed in BLPD-U (P<0.001). The difference of CD11c expression was also statistically significant between MCL and other B-LPD (P<0.01). In comparison of MCL with other B-LPD, there was a significant difference in the expression of CD11c (P<0.01). The expression of CD23 and sIgM in MCL are 7%-21% and 82%-100% respectively in Western population, while the expression of other immunophenotypic markers is similar with our study.

Conclusion: The significant high incidence of CD23 and low incidence of sIgM compared to the Western population was observed in Chinese patients, and CD11c coud serve as a useful marker to distinguish MCL from CLL and other CD5⁺ B-LPD.