Furthermore, the HDAC gene family was extensively amplified in 76.65% (197/257) of all sarcoma samples with different subtypes in TCGA cohort and were particularly amplified in fibrosarcoma (22/24, 91.67%), undifferentiated sarcoma (34/34, 100%) and leiomyosarcoma samples (76/101, 75.25%) (online supplemental figure S3). This evidence concerns the gene HDAC9 and undifferentiated (embryonal) sarcoma.