SHH and neoplasm: In this context, recent studies have identified four molecular subtypes of MDB tumours depending on the activation of specific embryonic developmental pathways which are, in particular, Wnt subgroup, characterized by somatic mutations occurring in the CTNNB1 gene [4–6], Sonic hedgehog (SHH) subgroup, mainly characterized by the loss of the SHH receptor Patched 1 (PTCH1) [4], a third subgroup (named Group 3) particularly enriched for MYC (c-Myc) gene amplifications, and subgroup four (named Group 4), in which tumours often possess amplification at the level of MYCN and CDK6 genes [7, 8].