[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Female genital tract](https://durgical.com/en/general-pathology/areas/female-genital/) › Endometriosis and adenomyosis # Endometriosis and adenomyosis - Lesion Endometrial tissue living where it should not: outside the uterus in endometriosis, inside the muscle wall in adenomyosis. Both bleed with each cycle and hurt. Updated Nov 12, 2026 ## Key points - Sites: ovaries, uterine ligaments, rectovaginal septum, pouch of Douglas, pelvic peritoneum; less often bowel, bladder, scars, and rarely lung. - Origin theories: retrograde menstruation (regurgitation), spread by vessels and lymphatics, coelomic metaplasia of the peritoneum, and stem or progenitor cells. - Implants overexpress aromatase (local estrogen), make prostaglandin E2 and cytokines, and resist progesterone. - Gross: red-blue to brown powder-burn spots, dense adhesions, and ovarian endometriomas (chocolate cysts) full of old blood. - Diagnosis needs two of three: endometrial glands, endometrial stroma, hemosiderin. - Adenomyosis: endometrium deep in the myometrium; enlarged globular uterus, heavy and painful periods. ## What it is Endometriosis is endometrial glands and stroma outside the uterus, most often on the ovaries and pelvic peritoneum; adenomyosis is the same tissue inside the myometrium. Endometriotic implants respond to hormones, bleed with the cycle and set up chronic inflammation and scarring, which explains pain and infertility. The implants make their own estrogen through aromatase and resist progesterone, and some carry cancer-driver mutations: endometriosis is the soil of ovarian endometrioid and clear cell carcinoma. ## Structure - Peritoneal implants: small nodules or spots with hemosiderin-laden macrophages and surrounding fibrosis. - Endometrioma: an ovarian cyst lined by endometrial-type epithelium and stroma, often replaced by hemosiderin-laden macrophages; thick brown fluid. - Deep endometriosis: nodules of glands and stroma in smooth-muscle and fibrous tissue of the rectovaginal septum or bowel wall. - Adenomyosis: nests of endometrial glands and stroma well below the endometrial-myometrial junction, surrounded by hypertrophic smooth muscle; the wall is thick and trabeculated with small hemorrhagic spaces. ## Step by step - Endometrial cells reach the pelvis, most often by retrograde flow during menstruation. - Some cells survive and attach, helped by immune tolerance, local inflammation and possibly somatic mutations. - The implants make estrogen through aromatase and resist progesterone, so they grow and bleed with each cycle. - Bleeding and prostaglandins recruit macrophages and cytokines, causing pain and fibrosis. - Adhesions distort the tubes and ovaries (infertility); rarely an implant progresses to endometrioid or clear cell carcinoma. ## Markers - CD10 (endometrial stroma) - ER and PR - ARID1A loss (in associated carcinomas) ## Clinical notes - Dysmenorrhea, deep dyspareunia, chronic pelvic pain, pain on defecation, and infertility; the severity of pain does not match the extent of disease. - Affects about one in ten women of reproductive age; it improves in pregnancy and after menopause. - Adenomyosis causes heavy, painful periods and a tender, uniformly enlarged uterus, often coexisting with leiomyomas or endometriosis. ## Memory aid Endometriosis is a lining that left home and still bleeds every month; adenomyosis is the lining that moved into the basement. ## Test yourself Think of the answer, then tap the question to see it. ## What three findings support a histologic diagnosis of endometriosis? Endometrial-type glands, endometrial stroma and hemosiderin pigment; two of the three suffice. ## What is the most accepted theory of how endometriosis begins? Retrograde menstruation: endometrial fragments flow back through the tubes and implant on pelvic surfaces. ## Which ovarian carcinomas arise from endometriosis? Endometrioid and clear cell carcinomas, often with ARID1A mutations. ## How does adenomyosis differ from endometriosis? In adenomyosis the endometrial tissue lies within the myometrium, causing an enlarged globular uterus with heavy painful periods; in endometriosis it lies outside the uterus. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/general-pathology/endometriosis-and-adenomyosis/) [More Pathology questions →](https://durgical.com/en/practice/?f=pathology) ## Elsewhere in DurgiPedia - [Aromatase (CYP19A1)](https://durgical.com/en/biochemistry/enzymes/aromatase/) - [Uterus and the endometrial cycle](https://durgical.com/en/histology/uterus-and-the-endometrial-cycle/) - [Actions of estrogen and progesterone](https://durgical.com/en/physiology/actions-of-estrogen-and-progesterone/) ## Connections ## Related 8 - [Endometrioid, clear cell and Brenner tumours of the ovary](https://durgical.com/en/general-pathology/endometrioid-clear-cell-and-brenner-tumours-of-the-ovary/) - [Non-neoplastic ovarian cysts and polycystic ovaries](https://durgical.com/en/general-pathology/non-neoplastic-ovarian-cysts-and-polycystic-ovaries/) - [Endometrium and abnormal uterine bleeding](https://durgical.com/en/general-pathology/endometrium-and-abnormal-uterine-bleeding/) - [Uterine leiomyoma](https://durgical.com/en/general-pathology/uterine-leiomyoma/) - [Metaplasia](https://durgical.com/en/general-pathology/metaplasia/) - [Chronic inflammation: causes, cells and features](https://durgical.com/en/general-pathology/chronic-inflammation-causes-cells-and-features/) - [Fibrosis in organs: TGF-β and the myofibroblast](https://durgical.com/en/general-pathology/fibrosis-in-organs-tgf-and-the-myofibroblast/) - [Precancerous conditions: when chronic inflammation, metaplasia or hyperplasia raise the risk](https://durgical.com/en/general-pathology/precancerous-conditions-when-chronic-inflammation-metaplasia-or-hyperplasia-rais/) ## Related conditions 7 - [Endometriosis](https://durgical.com/en/conditions/endometriosis/) - [Adenomyosis](https://durgical.com/en/conditions/adenomyosis/) - [Dysmenorrhoea](https://durgical.com/en/conditions/dysmenorrhoea/) - [Female infertility](https://durgical.com/en/conditions/female-infertility/) - [Ovarian cyst](https://durgical.com/en/conditions/ovarian-cyst/) - [Ovarian cancer](https://durgical.com/en/conditions/ovarian-cancer/) - [Abnormal uterine bleeding](https://durgical.com/en/conditions/abnormal-uterine-bleeding/) [← All of general pathology](https://durgical.com/en/general-pathology/) Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Endometriosis](https://www.ncbi.nlm.nih.gov/books/NBK567777/) (StatPearls (NCBI Bookshelf), 2026); [Adenomyosis](https://www.ncbi.nlm.nih.gov/books/NBK539868/) (StatPearls (NCBI Bookshelf), 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/general-pathology/endometriosis-and-adenomyosis/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/endometriosis-and-adenomyosis/