Based on our study and recent studies by Vokuhl et al. [38] and Cornet et al. [41], all SCUD-HB with loss of INI1 nuclear staining and small cell morphology are confirmed to have SMARCB1 deficiencies, supported with analysis utilizing FISH, multiplex ligation dependent probe amplification, and copy number loss of SMARCB1. Our study confirmed that SMARCB1 copy number loss is the defining feature of this tumor, with no other significant driver mutations detected utilizing our targeted 467 gene panel (see Supplementary Table S1 for list of genes included in panel). This evidence concerns the gene SMARCB1 and neoplasm.