Adenosarcoma of uterus, light micrograph. Mullerian adenosarcoma of the uterus is a biphasic tumour consisting of sarcomatous stroma and a benign glandular component. It forms a polypoid mass that can fill up the endometrial cavity. The sarcomatous stroma is usually low-grade. However, some cases can show sarcomatous overgrowth with high-grade spindle cells showing greater cytologic atypia and brisk mitotic activity (as depicted here).