NOTCH1 and B-cell chronic lymphocytic leukemia: Here we describe the most representative non‐coding lesion of the CLL genome, including lesions in the 3′‐UTR region of NOTCH1 which result in the truncation of the NOTCH1 protein PEST domain, and non‐coding mutations in an enhancer region on chromosome 9p13 which result in reduced expression of the PAX5 transcription factor.