It was introduced as its own entity within the World Health Organization (WHO) classification of CNS tumors in 2000.2 Currently, AT/RT is typically distinguished by immunohistochemical (IHC) staining demonstrating a loss of INI1 expression.3 We now know that most AT/RTs harbor pathogenic variants in the SMARCB1 (INI-1) gene at chromosomal band 22q11.2. Here, SMARCB1 is linked to ataxia telangiectasia.