BWSp neuroblastomas either have an overexpression of IGF2 (IC1 GOM or upd(11)pat) and/or CDKN1C reduction (upd(11)pat or CDKN1C loss-of-function mutations), which might be the relevant “first hit” for parts of the sympathetic nervous system to pave the road for neuroblastoma development due to a second alteration such as MYCN amplification. This evidence concerns the gene CDKN1C and neuroblastoma.