Endometrial stromal sarcoma that presented as a huge central cavity mass.An ill defined, septated cystic mass with a solid portion is noted in the uterine central cavity in patient 9. The endometrium is obliterated by the mass and myometrial thinning is noted (arrow).Pathology revealed a low grade endometrial stromal sarcoma invading the endometrium and almost the full thickness of the anterior myometrium and cystic degeneration of the tumor (not shown).