CDKN1A and neuroblastoma: MYCN-not-amplified neuroblastomas, showing a low level of MYCN, displayed two distinct patterns: (i) 30% of cases were characterized by low miR-17-5p expression and high-level of p21 (group 2); (ii) 70% of samples unexpectedly showed an elevated expression of miR-17-5p, associated with moderate downmodulation of p21 (group 3), less pronounced than in group 1.