Patients with BCR encoded by unmutated immunoglobulin variable heavy-chain genes (IGHV) (206, 207) along with ZAP70 expression (207–209) represent aggressive disease phenotype as compared to normal B cells or most CLL cases with mutated IgVH that lacks ZAP70 expression. This evidence concerns the gene ZAP70 and B-cell chronic lymphocytic leukemia.