The deletion in 13q14, involving the DLEU1 and DLEU2 genes as well as the microRNAs miR-16-1 and miR-15a, is the most common cytogenetic lesion in patients with CLL, being present in more than 50% of cases at diagnosis and strongly associated with a favorable prognosis when found as the sole abnormality [41]. This evidence concerns the gene DLEU1 and B-cell chronic lymphocytic leukemia.