[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/) › Uterine leiomyoma # Uterine leiomyoma - Lesion Fibroids are benign smooth-muscle tumours, the most common tumour in women; they grow with hormones and cause bleeding, pressure and fertility problems. Updated Nov 12, 2026 ## Key points - Location: intramural (most), submucosal (bleeding and infertility), subserosal or pedunculated, and rarely parasitic or cervical. - Gross: sharply circumscribed, firm, grey-white nodules with a whorled cut surface; usually multiple. - Micro: bundles of uniform spindle smooth-muscle cells with cigar-shaped nuclei and few mitoses; no tumour necrosis. - Genetics: MED12 mutations in most; HMGA2 rearrangements; fumarate hydratase loss in hereditary leiomyomatosis and renal cell cancer. - Degenerations: hyaline, cystic, calcification, and red (haemorrhagic) degeneration in pregnancy, which is painful. ## What it is Leiomyomas are benign clonal tumours of uterine smooth muscle and the most common tumour of women, found in a large share of women by menopause and more often and earlier in Black women. Most carry MED12 mutations or HMGA2 rearrangements; a few arise from germline fumarate hydratase mutation in a syndrome that also causes kidney cancer. They grow under estrogen and progesterone and shrink after menopause, and they essentially never turn into leiomyosarcoma. ## Structure - Cut surface bulges and shows a whorled, trabecular pattern; degenerating tumours show soft, cystic or calcified areas. - Variants: cellular leiomyoma; leiomyoma with bizarre nuclei (scattered atypical cells but no necrosis and few mitoses); lipoleiomyoma; fumarate hydratase–deficient leiomyoma (eosinophilic nucleoli with halos). - Unusual growth: intravenous leiomyomatosis (plugs in veins), benign metastasizing leiomyoma (nodules in the lung), disseminated peritoneal leiomyomatosis. ## Step by step - A single myometrial cell acquires a MED12 mutation or HMGA2 rearrangement. - Estrogen and progesterone stimulate its clone to divide and to make abundant extracellular matrix. - The nodule enlarges, compresses surrounding muscle and distorts the cavity or the outer contour. - When it outgrows its blood supply, it degenerates (hyalinisation, cysts, infarction, calcification). - After menopause, falling hormones shrink it. ## Markers - Desmin and smooth-muscle actin - ER and PR - Fumarate hydratase loss (hereditary form) ## Clinical notes - Many are silent; others cause heavy menstrual bleeding with iron-deficiency anaemia, pelvic pressure, urinary frequency and pain. - Submucosal fibroids impair implantation; in pregnancy they can cause miscarriage, malpresentation, obstructed labour and postpartum bleeding. - Young patients with many fibroids and skin leiomyomas, or with a family history of kidney cancer, should be considered for the fumarate hydratase syndrome. ## Memory aid A fibroid is a muscle knot that grows on hormones and stays benign: whorled, white and well behaved. ## Test yourself Think of the answer, then tap the question to see it. ## Which gene is mutated in most uterine leiomyomas? MED12; HMGA2 rearrangements account for another group. ## What is red degeneration of a leiomyoma? Haemorrhagic infarction of a fibroid, typically in pregnancy, causing acute pain. ## Which inherited syndrome links uterine leiomyomas with kidney cancer? Hereditary leiomyomatosis and renal cell cancer, from germline fumarate hydratase mutation. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/general-pathology/uterine-leiomyoma/) [More Pathology questions →](https://durgical.com/en/practice/?f=pathology) ## Elsewhere in DurgiPedia - [Actions of estrogen and progesterone](https://durgical.com/en/physiology/actions-of-estrogen-and-progesterone/) ## Connections ## Related 6 - [Uterine leiomyosarcoma vs leiomyoma](https://durgical.com/en/general-pathology/uterine-leiomyosarcoma-vs-leiomyoma/) - [Endometrium and abnormal uterine bleeding](https://durgical.com/en/general-pathology/endometrium-and-abnormal-uterine-bleeding/) - [Endometrial stromal tumours](https://durgical.com/en/general-pathology/endometrial-stromal-tumours/) - [Papillary, chromophobe and the rarer renal cell carcinomas](https://durgical.com/en/general-pathology/papillary-chromophobe-and-the-rarer-renal-cell-carcinomas/) - [Benign vs malignant tumours: the comparison table](https://durgical.com/en/general-pathology/benign-vs-malignant-tumours-the-comparison-table/) - [Hereditary cancer syndromes: the table to know](https://durgical.com/en/general-pathology/hereditary-cancer-syndromes-the-table-to-know/) ## Related conditions 7 - [Uterine fibroids (leiomyomas)](https://durgical.com/en/conditions/uterine-fibroids/) - [Abnormal uterine bleeding](https://durgical.com/en/conditions/abnormal-uterine-bleeding/) - [Female infertility](https://durgical.com/en/conditions/female-infertility/) - [Miscarriage (early pregnancy loss)](https://durgical.com/en/conditions/miscarriage/) - [Renal cell carcinoma](https://durgical.com/en/conditions/renal-cell-carcinoma/) - [Postpartum haemorrhage](https://durgical.com/en/conditions/postpartum-haemorrhage/) - [Iron deficiency anaemia](https://durgical.com/en/conditions/iron-deficiency-anaemia/) [← 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: [Uterine Leiomyomata](https://www.ncbi.nlm.nih.gov/books/NBK546680/) (StatPearls (NCBI Bookshelf), 2026); [Hereditary leiomyomatosis and renal cell cancer: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/hereditary-leiomyomatosis-and-renal-cell-cancer/) (MedlinePlus, US National Library of Medicine, 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/uterine-leiomyoma/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/uterine-leiomyoma/