NOTCH1 and B-cell chronic lymphocytic leukemia: Over the last 10 years, whole-exome and/or whole-genome sequencing studies have dissected the genomic landscape of CLL, demonstrating that only a few recurrent gene mutations are present in more than 5–10% of cases (ATM, NOTCH1, SF3B1, TP53), while the majority are seen in a minor proportion of cases (<1–5%) [20, 21, 32].