PCR analysis confirms the presence of monoclonal Ig_H rearrangements. Two seminested PCR reactions were performed to detect FrII-Ig_H and FrIII-Ig_H rearrangements on genomic DNA. PB DNA was obtained from 3 cases carrying a classic CLL-like (case 2), an atypical CLL-like (case 11), and a non–CLL-like (case 16) monoclonal B-cell population. PCR products have been visualized under transillumination after separation onto 10% (for FrII-Ig_H) and 15% polyacrylamide gels (for FrIII-Ig_H). NC and PC indicate negative and positive control (MEC-1 B-cell line³⁰ ).