Different miRNAs can increase or decrease PTEN levels—including those derived from miRNA precursors containing a single hairpin structure (e.g., miR-21, miR-22 and miR-205), as well as those with a polycistronic structure (e.g., mir-17-92, mir-106b-25, mir-367-302b and mir-221-222)—thus playing a role as a tumor suppressor or tumor promoter, respectively [21]. This evidence concerns the gene PTEN and neoplasm.