PTCH1 and medulloblastoma: Adult medulloblastoma may only comprise three of the four molecular groups, with group 3 tumors being extremely rare.6,42 The WNT subgroup occurs in children >4 years and adults, although only children in this subgroup show favorable outcomes, an association not always seen in patients older than 16.5,6 Most adult medulloblastoma have classic or desmoplastic histology; 50–60% belong to the SSH group, often involving mutations in PTCH1 or SMO.