Immunophenotyping of subtypes of B-chronic (mature) lymphoid leukemia. A study of 242 cases

The French-American-British group's proposal for the classification of chronic lymphoid leukemias is unique at this time. Testing, expanding, and adding to the theory by immunophenotyping will help to additionally characterize this group of diseases.

Peripheral blood samples from 242 patients with chronic lymphoid leukemias were analyzed for immunologic evaluation of the following subtypes: typical chronic lymphocytic leukemia (CLL), 189; CLL with pleomorphic lymphocytes (CLL-pleo), 19; CLL of mixed cell type (CLL/PL), 20; prolymphocytic leukemia (PLL), 22; hairy cell leukemia (HCL), 10; HCL-variant, 1; and splenic lymphoma with villous lymphocytes, 1.

The phenotype of CLL and CLL-pleo was weak surface immunoglobulin (SIg) with positive results of mouse rosettes (MR+), CD5+, and CD22-. Of PLL and HCL, it was strong SIg, MR-, CD5-, and CD22+. By analyzing the four markers and accepting the relevant results of two or more as sufficient for diagnosis, all cases (100%) of CLL, CLL-pleo, PLL, and HCL were diagnosed. CLL/PL showed the phenotype of CLL in 66.67% and of PLL in 33.33% of patients. The frequency of cases with weak fluorescence in decreasing order was CLL, CLL-pleo, CLL/PL, and PLL and HCL. The same sequence applied to the mean percentage of mouse rosette-forming cells and CD5 cells, but the sequence was reversed for CD22 cells.

SIg intensity, MR, CD5, and CD22 constitute the minimum number of immune markers for the differential diagnosis of the subtypes of chronic lymphoid leukemia. The frequency of the four markers among the subtypes suggested that CLL and CLL-pleo have identical phenotypes and that the five subtypes follow a continuous range of B-cell differentiation from early mature (CLL and CLL-pleo) to late mature pre-plasma cell stages (PLL followed by HCL), with CLL/PL of intermediate maturity.