Endometriosis is a disorder in which tissue similar to the lining of your uterus grows outside of your uterine cavity. It can cause painful symptoms that may get worse with hormone fluctuations and may affect your fertility. Learn about the diagnosis, treatment options, and complications of endometriosis . Endometriosis is a chronic, inflammatory gynecological condition defined by the presence of endometrial-like epithelium and/or stroma outside of the uterus ( Fig. 1 ). Endometriosis exists on a spectrum of presentations and can be further classified by location into superficial peritoneal (lesions involving the peritoneal surface), ovarian (formation of endometriomas or “chocolate cysts” on the ovaries typically containing ectopic tissue and bloody fluid), deep (nodular implantation of ... Endometriosis is defined as the presence of normal endometrial mucosa (glands and stroma) abnormally implanted in locations other than the uterine cavity (see the image below). Approximately 30-40% of women with endometriosis will be subfertile. Endometriosis is a condition where tissue similar to the lining of your uterus grows on other parts of your body. It can cause pelvic pain, heavy periods, infertility and other complications. Learn how to diagnose and treat endometriosis with Cleveland Clinic.