Review ArticlesEndometriosis: A Comprehensive ReviewArafah, Maria MD*; Rashid, Sameera MD†; Akhtar, Mohammed MD, FCAP, FRCPath, FRCPA†Author Information *Department of Pathology, King Saud University, Riyadh, Saudi Arabia †Department of Laboratory Medicine and Pathology, Hamad Medical Corporation, Doha, Qatar The authors have no funding or conflicts of interest to disclose. All figures can be viewed online in color at www.anatomicpathology.com. Reprints: Maria Arafah, MD, Department of Pathology, King Saud University, Riyadh 11421, Saudi Arabia (e-mail: [email protected]). Advances In Anatomic Pathology: January 2021 - Volume 28 - Issue 1 - p 30-43 doi: 10.1097/PAP.0000000000000288 Buy Metrics Abstract Endometriosis is a relatively common condition in which endometrial tissue is established in locations outside the uterus where, like the eutopic endometrium, it responds to hormonal stimuli and develops internal bleeding, inflammation, and fibrosis. These changes are associated with chronic and often debilitating cyclic pain and infertility. The pathogenesis of endometriosis is multifactorial, and several theories have been proposed to explain it. These include retrograde menstruation, celomic metaplasia, embryologic rests, and lymphovascular spread. Hormones, immunologic status, and genetic factors may also play a role. In most patients, the disease involves pelvic organs, but rarely it may also extend to a large variety of distant locations in the body. Patients with ovarian endometriosis are at higher risk for developing ovarian carcinomas including endometrioid and clear cell carcinomas. Some of these carcinomas may arise in a background of structural and/or nuclear atypia within the endometriotic foci. There is no known cure for endometriosis and treatment mostly consists of managing chronic pain or infertility. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.