MTHFR and primitive neuroectodermal tumor: In pediatric tumors, a case-control study of 73 Thai children with different types of brain tumors demonstrated that the CC allele of the MTHFR A1298C polymorphism was associated with a 3.9-fold increased risk of embryonic tumors such as medulloblastoma, pineoblastoma and primitive neuroectodermal tumor (PNET).