Monoclonal B-cell lymphocytosis (MBL) was defined by the International Familial CLL consortium in 2005 as a monoclonal B-cell lymphocyte population in the peripheral blood <5,000/uL without evidence of lymphadenopathy (i.e. SLL), an autoimmune/infectious disease or other features diagnostic of a B-cell lymphoproliferative disorder.  The 2016 WHO hematopathology revision dropped the requirement of cytopenias or disease related symptoms as adequate to make the diagnosis of CLL.