The importance of surface immunoglobulin, mouse rosettes, and CD5 in the immunophenotyping of chronic lymphocytic leukemia and reactive lymphocytosis.

Peripheral blood from 167 B-chronic lymphocytic leukemia (B-CLL) and 119 reactive lymphocytosis (RLC) patients were analyzed to evaluate the immunophenotypic diagnostic value of mouse rosettes (M-rosette), and weak expression of monoclonal surface immunoglobulin (SIg). In B-CLL, 145 cases were M-rosette+ (86.83%), 135 surface immunoglobulin (SIg)+ (80.84%), and 117 M-rosette+ SIg+ (70.06%). Of 32 SIg- cases, 28 were M-rosette+; and of 22 M-rosette-cases, 18 were SIg+. By combining results of the two assays and accepting positivity of either one or both as sufficient for diagnosis, B-CLL was diagnosed in 163 cases (97.60%). CD5 was performed in 49 cases of the 167 with paired data for SIg and M-rosettes. By combining the results of the three assays and accepting positivity of any two or all three as sufficient for diagnosis, all 49 cases (100%) were diagnosed. Correlation analysis showed no significant association between M-rosette, SIg, and CD5 expression. The results demonstrate the independent expression of the three markers, and their complementary role in immunophenotyping B-CLL. In RLC, all 119 cases were T-lineage and SIg-, and 115 were M-rosette-, indicating the role of the two markers in differentiating B-CLL from RLC. Three of the four M-rosette+ T-RLC were subsequently diagnosed as B-CLL, suggesting the necessity of follow-up of such cases.