NOTCH1 and B-cell chronic lymphocytic leukemia: Accordingly, del(13q), and to a lesser extent trisomy 12, are relatively early cytogenetic events which may frequently occur at an MBLlo stage, whereas del(17p), NOTCH1 mutations, and to a lesser extent also del(11q) and t(14q32), would typically arise later, as secondary cytogenetic events occurring at an MBLhi or CLL stage.