© American Society for Clinical Pathology Hematopathology / BICLONAL CLL WITH SEPARATE CLONAL ORIGINS Molecular Characterization of Chronic Lymphocytic Leukemia With Two Distinct Cell Populations Evidence for Separate Clonal Origins

We report a case of an elderly woman with persistent lymphocytosis in whom flow cytometric immunophenotyping revealed 2 distinct clonal B-cell populations with different light chain restrictions. One clone was CD19+ (dim), CD5+ (bright), CD23+ (moderate), and κ+; the other clone was CD19+ (moderate), CD5+ (bright), CD23+ (dim), and λ+. We separated the 2 clones by flow cytometry from peripheral blood lymphocytes for further molecular and cytogenetic analysis. Polymerase chain reaction (PCR) analysis of the immunoglobulin heavy chain (IgH) genes revealed that the clones had bands of slightly different size. The PCR products of the framework 3 (FR3) region were cloned, and sequence analysis confirmed that each population had distinct, clone