SMARCB1 and rhabdoid tumor: It is not possible to ascertain the mechanism of tumorigenesis without performing copy number analysis, however given the evidence for 22q deletion in rhabdoid tumor in association with SMARCB1 mutation it is likely that c157C>T is a hemizygous mutation and that the heterozygous genotypes are derived from amplicons where the DNA amplified is derived from both normal and tumor DNA.