NOTCH1 and B-cell chronic lymphocytic leukemia: Advances in the field have unraveled multiple clinical and biological risk factors for the development of RS, including an advanced stage of CLL [12,13], nonmutated IGHV [9,12], absence of del13q14, and mutated NOTCH1 [14,15], as well as inactivation of TP53 or del17p13 [2,13].