Endometriosis is a condition in which the tissue that forms the interior lining in the endometrium or the uterus grows outside the uterus as well. Normally, the endometrial tissue that lines the inside of the uterus thickens, sheds and bleeds out of the vagina during your monthly menstrual cycle.
However, the excessive tissue that grows outside the uterus gets trapped leading to the formation of cysts known as endometriomas. Severe endometriosis is usually accompanied by painful cramps during menstrual periods and may also lead to fertility problems. It can be treated with laparoscopic surgery for endometriosis.