College of American Pathologists classification system for uterine sarcomas

* Low-grade endometrial stromal sarcoma is distinguished from a benign endometrial stromal nodule by depth of myometrial invasion greater than or equal to 3 mm, lymphovascular invasion, or greater than or equal to 3 foci of myometrial invasion of any depth. Minor marginal irregularity in the form of tongues less than 3 mm is allowable for an endometrial stromal nodule. This checklist does not apply to endometrial stromal nodules.