SMARCB1 and atypical teratoid rhabdoid tumor: Inactivating mutations of the SMARCB1 gene (hSNF5/INI-1) at 22q11.2 is thought to be a crucial step in tumorigenesis (Biegel, 2006), but mutations can be identified in only about 76% of CNS ATRT tumor samples (Biegel et al., 2002).