Clonal B-cell lymphocytosis: a new member?

In this issue of Blood, Xochelli et al have identified, in otherwise healthy individuals with no clinical signs of lymphoproliferative disorders, a circulating clonal B-cell population with an immunophenotype consistent with a marginal zone B-cell population (CBL-MZ).1 This scenario is reminiscent of monoclonal B-cell lymphocytosis (MBL)2 of the "CD5-negative type," although the report includes cases with rather prominent B lymphocytosis (up to 34 × 109/L, K. Stamatopoulos, Institute of Applied Biosciences, Thessaloniki, Greece, written communication, December 16, 2013), being above the MBL threshold of 5 × 109 B lymphocytes/L2. © 2014 by The American Society of Hematology.