Admittedly, 35% of patients presenting with MRT have germline mutation of SMARCB1 (or SMARCA4), defining the rhabdoid predisposition syndrome 1 or 2 (RPS1; RPS2), respectively [7,8], but the emergence of a full-blown and indeed highly aggressive cancer so early in life, and hinging on the genomic inactivation of just this one gene, begs the question: what is the normal role of this gene such that its loss of function has such profound and devastating consequences? This evidence concerns the gene SMARCA4 and cancer.