THOP1 and undifferentiated (embryonal) sarcoma: In addition to the SMARCA4-THOP1 fusion gene, RNA-seq also identified an SMARCA4 splice-site mutation (c.3168+1G>A) (Fig. 3g), suggesting the diagnosis of SMARCA4-deficient undifferentiated sarcoma caused by biallelic inactivation of SMARCA424.