Fibroids and Cancer: What the Real Risk Is

Do fibroids turn into cancer?

Fibroids do not turn into cancer. A fibroid is a benign growth of uterine muscle, and decades of study show it does not become a cancerous tumor over time 1Ref 1Office on Women's Health (U.S. HHS) (2025).Uterine fibroids.Patient-facing overview stating fibroids are almost always benign, are very common (up to 80% of women by age 50), and that having fibroids does not raise uterine cancer risk.. According to the Office on Women's Health, fibroids are almost always harmless, and having them does not raise your risk of uterine cancer 1Ref 1Office on Women's Health (U.S. HHS) (2025).Uterine fibroids.Patient-facing overview stating fibroids are almost always benign, are very common (up to 80% of women by age 50), and that having fibroids does not raise uterine cancer risk.. Fibroids affect up to 80% of women by age 50, yet almost none ever become cancer 1Ref 1Office on Women's Health (U.S. HHS) (2025).Uterine fibroids.Patient-facing overview stating fibroids are almost always benign, are very common (up to 80% of women by age 50), and that having fibroids does not raise uterine cancer risk..

The confusion comes from a separate rare cancer, leiomyosarcoma, which starts in muscle and can look like a fibroid on imaging. Leiomyosarcoma is not a fibroid that went bad; it arises on its own 2Ref 2American College of Obstetricians and Gynecologists (2021).Management of Symptomatic Uterine Leiomyomas: ACOG Practice Bulletin, Number 228.ACOG practice bulletin reviewing that leiomyosarcoma is a distinct rare cancer, not a transformed fibroid, with prevalence estimates that vary widely and rise with age.. The two can look similar before surgery, but the odds strongly favor a benign fibroid. Our guide to fibroid symptoms and treatment covers the everyday, non-cancer picture.

What is leiomyosarcoma?

Leiomyosarcoma is a rare cancer of smooth muscle that can arise in the uterus. Unlike a fibroid, it grows quickly, can invade nearby tissue, and is a true malignancy from the start 2Ref 2American College of Obstetricians and Gynecologists (2021).Management of Symptomatic Uterine Leiomyomas: ACOG Practice Bulletin, Number 228.ACOG practice bulletin reviewing that leiomyosarcoma is a distinct rare cancer, not a transformed fibroid, with prevalence estimates that vary widely and rise with age.. It is uncommon at any age but becomes somewhat more likely after menopause, which is why new growth in that stage draws attention. New bleeding after menopause is also evaluated carefully because, although fibroids usually shrink after menopause, postmenopausal bleeding can occasionally signal endometrial cancer 3Ref 3National Cancer Institute (PDQ Adult Treatment Editorial Board) (2020).Endometrial Cancer Treatment (PDQ®)–Patient Version.NCI patient information identifying postmenopausal bleeding as a warning sign that warrants evaluation for endometrial (uterine) cancer..

Doctors cannot always distinguish a leiomyosarcoma from a fibroid with imaging alone, though certain features raise suspicion. Rapid growth, growth after menopause, and unusual MRI patterns can prompt further testing 4Ref 4Hartmann KE, Fonnesbeck C, Surawicz T, Krishnaswami S, Andrews JC, Wilson JE, Velez-Edwards D, Kugley S, Sathe NA (2017).Management of Uterine Fibroids (Comparative Effectiveness Review No. 195).Comparative effectiveness review discussing the difficulty of distinguishing benign fibroids from sarcoma before surgery and features that prompt further testing.. Even so, the great majority of masses that look like fibroids are exactly that.

How rare is fibroid cancer, really?

The chance that a presumed fibroid is actually cancer is low. Estimates of finding an unsuspected leiomyosarcoma during surgery for fibroids vary widely between studies, from well under 1 in 1,000 in younger women to higher figures in older women, and ACOG notes that the risk climbs with age 2Ref 2American College of Obstetricians and Gynecologists (2021).Management of Symptomatic Uterine Leiomyomas: ACOG Practice Bulletin, Number 228.ACOG practice bulletin reviewing that leiomyosarcoma is a distinct rare cancer, not a transformed fibroid, with prevalence estimates that vary widely and rise with age.. This uncertainty is exactly why guidelines urge individualized counseling rather than a single alarming number.

Context helps put the risk in proportion. Fibroids are extremely common, affecting up to 80% of women by age 50, yet leiomyosarcoma remains rare across that same group 1Ref 1Office on Women's Health (U.S. HHS) (2025).Uterine fibroids.Patient-facing overview stating fibroids are almost always benign, are very common (up to 80% of women by age 50), and that having fibroids does not raise uterine cancer risk.. For most women, especially before menopause, a fibroid-like mass is overwhelmingly likely to be benign. A heavy period is far more likely to reflect a benign fibroid than a cancer.

What red flags should prompt a check?

A few patterns justify prompt evaluation even though cancer stays unlikely. Bleeding after menopause, a fibroid that grows rapidly or grows at all after menopause, and new pelvic pain or a mass that enlarges quickly are the main red flags 3Ref 3National Cancer Institute (PDQ Adult Treatment Editorial Board) (2020).Endometrial Cancer Treatment (PDQ®)–Patient Version.NCI patient information identifying postmenopausal bleeding as a warning sign that warrants evaluation for endometrial (uterine) cancer.. These signs do not mean cancer is present; they mean the situation deserves a closer look.

Age shapes the risk across the lifespan. Fibroid-related cancer is very rare in the teens and reproductive years, when fibroids are common and almost always benign, and the small risk of leiomyosarcoma rises gradually after menopause 2Ref 2American College of Obstetricians and Gynecologists (2021).Management of Symptomatic Uterine Leiomyomas: ACOG Practice Bulletin, Number 228.ACOG practice bulletin reviewing that leiomyosarcoma is a distinct rare cancer, not a transformed fibroid, with prevalence estimates that vary widely and rise with age.. New pelvic pain of any kind is worth assessing, and our overview of new pelvic pain explains the broader workup.

When fibroid cancer worries need a gynecologist

A gynecologist can help you weigh a low risk against your specific findings. Sharing your age, your imaging, and any bleeding or rapid-growth history lets the clinician decide whether reassurance and monitoring are enough or whether extra testing makes sense 2Ref 2American College of Obstetricians and Gynecologists (2021).Management of Symptomatic Uterine Leiomyomas: ACOG Practice Bulletin, Number 228.ACOG practice bulletin reviewing that leiomyosarcoma is a distinct rare cancer, not a transformed fibroid, with prevalence estimates that vary widely and rise with age.. For most women, especially before menopause, the honest answer is that fibroids are benign and stay that way. Weighing your age, symptoms, and imaging together gives a far more accurate picture than any single statistic about risk 2Ref 2American College of Obstetricians and Gynecologists (2021).Management of Symptomatic Uterine Leiomyomas: ACOG Practice Bulletin, Number 228.ACOG practice bulletin reviewing that leiomyosarcoma is a distinct rare cancer, not a transformed fibroid, with prevalence estimates that vary widely and rise with age.. Bleeding after menopause always deserves evaluation, even when the likely cause is harmless 3Ref 3National Cancer Institute (PDQ Adult Treatment Editorial Board) (2020).Endometrial Cancer Treatment (PDQ®)–Patient Version.NCI patient information identifying postmenopausal bleeding as a warning sign that warrants evaluation for endometrial (uterine) cancer.. Gale can help you prepare for that conversation.