Based on TCGA, we determined that 3 of the most common subtypes of soft tissue sarcoma, undifferentiated pleomorphic sarcoma, myofibrosarcoma, and leiomyosarcoma (STS cohort), had recurrent alterations in the ATRX gene, which occurred in 24% of samples. This evidence concerns the gene ATRX and undifferentiated pleomorphic sarcoma.