CD5 and B-cell chronic lymphocytic leukemia: Analysis of the tumor IG rearrangements revealed that CLL is divided into two major biological subsets arising at different stages of differentiation, one with unmutated IG (U-CLL) derived from a restricted repertoire of pre-germinal center CD5+ve B-cells and another with mutated IG derived from post-germinal center CD5+ve B-cells (M-CLL) [14,15,16,17,18].