PTCH1 and medulloblastoma: Mutations resulting in overactivation and/or deregulation of Shh signaling, including loss of patched 1 (Ptch1), alter the development of CGNP, making them hyperproliferative and susceptible to malignant transformation into medulloblastoma (MB), the most common malignant pediatric brain tumor (Goodrich et al., 1997; Briscoe and Therond, 2013; Marshall et al., 2014).