The pelvic uterus-like mass--a primary or secondary Müllerian system anomaly?

The pelvic uterus-like mass is a rare phenomenon in which an extrauterine mass, comprised of smooth muscle and a central cavity lined by endometrium, is found within the pelvis. The mass is associated with endometriosis and in some of the cases with congenital Müllerian malformations. There is an ongoing debate whether the finding is a result of smooth muscle metaplasia or a remnant of a Müllerian system defect. We present 2 distinct cases of a uterus-like mass.