uterine sarcoma cell uterine leiomyosarcoma cell A rare type of uterine cancer that forms in muscle or other tissues of the uterus. It usually occurs after menopause. The two main types are leiomyosarcoma (cancer that begins in smooth muscle cells) and endometrial stromal sarcoma (cancer that begins in connective tissue cells). BTO:0003597 BrendaTissueOBO