The 13q14 region has been identified as a recombination hot spot [9] and includes the RB1, DLEU1, and DLEU2 genes and microRNAs MIR16-1 and MIR15A. Deletion of the 13q14.3 region distal to RB1 is the most common chromosomal abnormality found in CLL [10], and the DLEU2/MIR15A/MIR16-1 locus has been shown to play a role in controlling the expansion of mature B cells by down-regulating the genes that control entry into the cell cycle [11]. This evidence concerns the gene RB1 and B-cell chronic lymphocytic leukemia.