Representative flow cytometric profiles of CD38 expression on mutated and unmutated CD5⁺/CD19⁺ B-CLL cases. B-CLL cases were analyzed by flow cytometry after exposure to anti–CD19-APC, anti–CD5-FITC, and anti–CD38-PE. The events illustrated were obtained by gating on cells expressing CD19. Density plots of CD38 and CD5 expression are shown for 8 representative B-CLL cases. The upper 4 cases had less than 2% mutations in either the V_H or V_L genes, whereas the lower 4 cases had mutations in the V_H and/or V_L genes.