The tumor cells shown here have relatively more cytoplasm compared to the case seen in the previous three images. Numerous apoptotic cells are present. Molecular Genetics: Several genetic pathways have been implicated in the pathogenesis of medulloblastoma: (1) sonic hedgehog (SHH), (2) wingless (WNT), and (3) ERBB receptor tyrosine kinase I family. Two inherited syndromes associated with medulloblastomas have been described - Gorlin and Turcot syndromes. Gorlin syndrome results from inherited mutations in the hedgehog pathway gene PTCH. Mutations in hedgehog family members are also seen in 15% to 25% of sporadic medulloblastomas. Turcot syndrome is caused by germline mutations in the gene APC - a member of the WNT signaling pathway.