G-quadruplex in intron 3 of TP53 gene has been shown to regulate alternative splicing of p53 messenger RNA [21–24], and it has been demonstrated that G4 polymorphisms in haplotypes of the WT TP53 allele have an impact on Li-Fraumeni/Li-Fraumeni-like syndrome (LFS/LFL) penetrance in germline TP53 mutation carriers [24]. This evidence concerns the gene TP53 and Li-fraumeni-like syndrome.