A rare, high grade sarcoma that arises from the endometrial stroma. It is characterized by round cell morphology. It was previously also known as undifferentiated uterine sarcoma. In 2014, high grade endometrial stromal sarcoma was reclassified and is currently considered a distinct and rare neoplasm. It appears to have a prognosis that falls between low grade endometrial stromal sarcoma and undifferentiated sarcoma. [from
NCI]