Fibroids are benign, and they almost never turn into cancer. Doctors believe that the rare cancer that can look like a fibroid, called leiomyosarcoma, does not develop from an existing fibroid but arises on its own. Having fibroids does not raise your risk of uterine cancer. Because a sarcoma can occasionally be mistaken for a fibroid before surgery, careful imaging and attention to certain warning signs still matter.
Fibroids are benign
ACOG describes fibroids as "benign (not cancer) growths that develop from the muscle tissue of the uterus." They are the most common growth found in a woman's pelvis. The federal Office on Women's Health (OWH) adds three reassuring points:
- Doctors think uterine cancers of this type "do not arise from an already-existing fibroid."
- Having fibroids "does not increase the risk of developing a cancerous fibroid."
- Having fibroids "does not increase a woman's chances of getting other forms of cancer in the uterus."
So the honest answer to "can fibroids turn into cancer?" is: experts do not think they do. The real question is whether a growth that looks like a fibroid could be something else.
What leiomyosarcoma is, and how rare it is
Leiomyosarcoma (LMS) is a rare cancer of the uterine muscle. Before surgery it can look very much like a fibroid on an exam or scan. OWH estimates that a cancerous growth of this type occurs in fewer than 1 in 1,000 cases.
The U.S. Food and Drug Administration (FDA) looked at this closely in 2017, focusing on women having surgery for what were believed to be fibroids. It estimated:
| Finding in women having surgery for presumed fibroids | FDA 2017 estimate |
|---|---|
| Leiomyosarcoma | About 1 in 495 to 1 in 1,100, depending on the analytical method |
| Any uterine sarcoma | About 1 in 225 to 1 in 580 |
These figures come from women who were already having surgery, so they may not reflect every woman with fibroids. The FDA has also stated that "the risk of unsuspected cancer increases with age, particularly in women over 50."
Why this topic gets so much attention
Concern about hidden sarcoma grew after cases in which a power morcellator, a device that cuts tissue into small pieces so it can be removed through small incisions, spread an undetected cancer. In 2020 the FDA advised that when morcellation is appropriate, only contained morcellation (inside a bag) should be used, and that it should not be used for suspected fibroids in women who are postmenopausal or over 50.
ACOG's Committee Opinion 822 (2021) explains the core problem: "leiomyosarcoma cannot be reliably diagnosed preoperatively." That is why doctors weigh each woman's risk before any fibroid treatment and discuss the choices openly.
Questions about your treatment options? Dr. Fox can help.
Book a ConsultationThis article is part of our Fibroid Treatment Guide.
Does fast growth mean cancer?
Many women are told that a quickly growing fibroid might be cancer. The evidence for premenopausal women is more reassuring than that. In a 1994 study of 1,332 women at two hospitals who had surgery for presumed fibroids, only 1 had leiomyosarcoma. Among 371 women operated on for "rapid growth", the sarcoma rate was 0.27%, and none of the 198 who met a formal definition of rapid growth had a sarcoma. The authors concluded the data did not support a higher sarcoma risk with rapid growth. This was an older study at two community hospitals, so it is one piece of evidence rather than the final word.
Growth after menopause is different. Fibroids normally shrink when hormone levels fall, so a fibroid that grows after menopause needs evaluation. Insurer policies such as Aetna's list postmenopausal fibroid growth, or rapid growth at any time, as a possible sign of sarcoma and a reason not to proceed with embolization until it is assessed. Read more in fibroids after menopause.
Why imaging and evaluation matter before treatment
No scan can rule out sarcoma with complete certainty, but imaging helps. A radiology review notes that MRI findings that clearly separate a fibroid from leiomyosarcoma "have yet to be clearly established", while invasion into surrounding tissue, areas of bleeding and dead tissue, or rapid growth are suggestive of cancer. A 2026 review describes newer approaches, such as computer analysis of MRI images, that show promise in improving this.
Evaluation matters for every treatment, but especially for uterine fibroid embolization. Surgery removes tissue that a pathologist examines under a microscope. Uterine fibroid embolization (UFE) shrinks fibroids in place, so no tissue is examined. That is why the European interventional radiology standards (CIRSE 2015) name contrast-enhanced MRI as the preferred imaging test before the procedure and list cancer of the uterus or ovaries as a reason not to do it. Many doctors also sample the lining of the uterus or update cervical screening when bleeding is abnormal. See ultrasound vs MRI for fibroids and who is a candidate for UFE.
After any uterus-sparing treatment, follow-up imaging and symptom checks help confirm the fibroids are responding. A fibroid that keeps growing after treatment should be re-evaluated.
Warning signs to report
None of these means you have cancer, but each deserves a prompt visit:
- Any vaginal bleeding after menopause. ACOG notes that bleeding is the presenting sign in more than 90% of postmenopausal women with endometrial cancer, which is a different cancer from sarcoma but is also checked for.
- A fibroid or uterus that grows after menopause
- A fibroid that keeps growing after treatment
- New pelvic pain, pressure or bleeding between periods without a clear cause
Questions to ask your doctor
If you are worried about cancer, it is completely reasonable to ask directly. Some useful questions:
- Is there anything on my imaging that looks unusual for a fibroid?
- Do my age or symptoms change my risk?
- Do I need an MRI, a sample of the uterine lining, or other tests before treatment?
- How will you check that my fibroids are responding after treatment?
- What changes should prompt me to call you?
A good answer will be specific to you. Because sarcoma is rare, most women hear that their findings look typical for fibroids, which is reassuring and lets the conversation move on to how to relieve their symptoms.
The bottom line
Fibroids are benign, they are not thought to turn into cancer, and having them does not raise your risk of uterine cancer. Rare sarcomas can resemble fibroids, so good imaging and a careful history are part of choosing any treatment. If you are weighing options, start with our fibroid treatment guide.
Frequently Asked Questions
Can a fibroid become cancerous?
Experts do not think so. The Office on Women's Health states that doctors believe leiomyosarcoma does not arise from an existing fibroid, and that having fibroids does not increase cancer risk.
How common is leiomyosarcoma?
It is rare. The FDA's 2017 estimate for women having surgery for presumed fibroids was about 1 in 495 to 1 in 1,100, and the risk rises with age, particularly over 50.
Can an MRI tell if a fibroid is cancer?
MRI helps, and certain features raise suspicion, but no scan can rule out sarcoma with complete certainty. ACOG notes leiomyosarcoma cannot be reliably diagnosed before surgery.
Does a fast-growing fibroid mean cancer?
Not usually in premenopausal women; a 1994 study of 1,332 women did not find a higher sarcoma rate with rapid growth. A fibroid that grows after menopause, however, should be evaluated promptly.
Is it safe to have UFE if cancer cannot be fully ruled out?
Doctors reduce the risk with a careful history, imaging (usually MRI) and other tests before UFE, and known cancer is a reason not to do it. Discuss your individual risk factors with your doctor.
Keep Reading
- Uterine Fibroid Embolization (UFE) in New York City
- Fibroids After Menopause: What Changes and What to Watch For
- Fibroid Diagnosis: Ultrasound vs MRI
- Am I a Candidate for UFE? A Practical Checklist
- Degenerating Fibroid: Symptoms and When to Go to the ER
- What Are Uterine Fibroids?
- Fibroid Treatment Guide: every option, compared
Sources
- FDA, 2017 — updated assessment of the use of laparoscopic power morcellators to treat uterine fibroids
- FDA safety communication, 2020 — perform only contained morcellation when laparoscopic power morcellation is appropriate
- ACOG Committee Opinion No. 822, Obstet Gynecol, 2021 — uterine morcellation for presumed leiomyomas
- Office on Women's Health — Uterine fibroids (updated February 2025)
- ACOG patient FAQ — Uterine Fibroids (last reviewed December 2025)
- Parker, Fu and Berek, Obstet Gynecol, 1994 — uterine sarcoma in patients operated on for presumed and rapidly growing leiomyoma (1,332 women)
- Kido et al., Radiographics, 2003 — diffusely enlarged uterus: evaluation with MR imaging
- Albastawisy et al., Clin Radiol, 2026 — MRI of the myometrium: benign and malignant disease
- van Overhagen and Reekers, Cardiovasc Intervent Radiol, 2015 — CIRSE standards of practice for uterine artery embolization
- Aetna Clinical Policy Bulletin 0304 — fibroid treatment
- ACOG Committee Opinion No. 734, Obstet Gynecol, 2018 — transvaginal ultrasound in postmenopausal bleeding
Medically reviewed by David Fox, MD, FACS, RPVI. This article is general information, not a substitute for a medical evaluation.
Living with heavy periods, pelvic pressure or other fibroid symptoms? Schedule a consultation with Dr. David Fox at Fox Vein & Vascular in Manhattan to find out whether uterine fibroid embolization is right for you. Call (212) 362-3470 or request a UFE consultation online.
