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.
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.
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.
Elsewhere in DurgiPedia
Connections
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 (StatPearls (NCBI Bookshelf), 2026); Hereditary leiomyomatosis and renal cell cancer: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026).
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Representative model, for educational purposes only.