PHF1 and endometrioid stromal sarcoma: The majority of low-grade endometrial stromal sarcomas (LG-ESSs) harbor a fusion gene, most commonly involving JAZF1, SUZ12, and/or PHF1 genes, i.e., JAZF1-SUZ12 fusion (80%), JAZF1-PHF1 fusion (6%), or EPC1-PHF1 fusion (4%) [10–12].