Indeed, compared with IGHV mutated (M-CLL) cases, the more aggressive U-CLL subtype exhibited an increased expression of cell cycle genes, including ATF2, CCNB2, CDC20, CDC25A, CREB1, E2F4, ESR1, FOXM1, MKI67, MYC, POU2F2, RBL2, SP3, TYMS, UBE2C, VRK1. This evidence concerns the gene ESR1 and B-cell chronic lymphocytic leukemia.