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PubMed This is a summary of 21 peer-reviewed journal articles Updated
Gynecology · Uterine Polyp and Uterine Fibroid

What Is the Difference Between Uterine Polyps and Fibroids?

At a Glance

A uterine polyp grows from the lining and often causes spotting, while a fibroid grows from the uterine muscle and more often causes heavy bleeding or pressure. Ultrasound can suggest the difference, but tissue examination may be needed for certainty.

In this answer

5 sections

01

Location Matters

02

Symptoms: Bleeding, Pain, and Fertility

03

Why Ultrasound Isn’t Always Definitive

04

Cancer Risk and Diagnosis

05

Evaluation and Treatment

The main difference between a uterine polyp and a uterine fibroid is where they start growing. A polyp is a localized overgrowth of the endometrium (the lining of the uterus) that protrudes into the uterine cavity [1][2]. A fibroid (also called a leiomyoma) is a benign tumor (a non-cancerous growth) made of smooth muscle that arises in the myometrium (the muscular wall of the uterus) [1][3].

While most polyps and fibroids are benign, they can cause similar symptoms and look alike on early imaging. Understanding their differences can help explain your symptoms and guide your management.

Location Matters

Where the growth is located affects symptoms and treatment.

  • Polyps grow from the uterine lining and hang into the uterine cavity [1].
  • Fibroids grow in the muscle wall, but they are categorized by how they grow [3]:
    • Submucosal fibroids bulge into the uterine cavity (and can easily be mistaken for polyps).
    • Intramural fibroids remain completely within the muscular wall.
    • Subserosal fibroids push outward from the outside of the uterus.

Symptoms: Bleeding, Pain, and Fertility

Both polyps and fibroids can cause abnormal bleeding, but their typical patterns often differ, and they may cause different secondary symptoms:

  • Bleeding Patterns: Polyps are most characteristically associated with spotting or bleeding between periods (intermenstrual bleeding) [4][5]. Fibroids are a common cause of heavy, prolonged menstrual bleeding [4][5]. However, there is overlap: polyps can sometimes cause heavy periods, and fibroids can cause spotting.
  • Other Symptoms: Fibroids, especially large ones, can cause pelvic pressure, pain, urinary frequency, or constipation [3]. Polyps typically do not cause pressure symptoms.
  • Impact on Fertility: Both conditions may make it harder to conceive or maintain a pregnancy, though many women with polyps or fibroids conceive normally. Polyps and submucosal fibroids can physically distort the space inside the uterus and alter the local environment of the uterine lining, which may interfere with an embryo’s ability to implant [6][7]. Intramural and subserosal fibroids have less impact on fertility.

When to Seek Immediate Care: Very heavy bleeding that quickly soaks through pads, or bleeding accompanied by dizziness, faintness, or shortness of breath, requires urgent medical evaluation. Any bleeding after menopause should also be evaluated promptly by a doctor [8].

Why Ultrasound Isn’t Always Definitive

A standard transvaginal ultrasound (TVUS) is usually the first test to evaluate abnormal bleeding. While it can detect a mass, an ultrasound is an image, not a definitive tissue diagnosis [9][10]. A submucosal fibroid can look very similar to a large polyp [9].

To better evaluate the mass, doctors may use:

  • Doppler Blood Flow: Doctors use color Doppler to look at blood vessels. Polyps often have a single feeding blood vessel, while fibroids typically have a circular or multiple-vessel blood flow pattern [11][12][13]. This pattern is a helpful clue but does not provide a definitive answer [14][12].
  • Saline-Infusion Sonohysterography: If a standard ultrasound is unclear, sterile saline (saltwater) can be gently placed into the uterus during an ultrasound. This creates an outline of the mass, significantly improving the ability to see whether it is attached to the lining or pushing from the muscle wall [15][16].

Cancer Risk and Diagnosis

Both polyps and fibroids are almost always benign.

In broad studies, an estimated 2.7% of polyps may contain pre-cancerous or cancerous cells [17]. However, this risk is higher in women who have gone through menopause, those with abnormal bleeding, or those with other risk factors like obesity [17][18]. Fibroids are very rarely cancerous, but it is impossible for any imaging test to prove with 100% certainty that a presumed fibroid is benign [3].

Because imaging cannot provide a definitive diagnosis, looking at the tissue under a microscope (pathology) is the only way to be absolutely sure of the diagnosis [8][9][3].

Evaluation and Treatment

Not every polyp or fibroid requires removal. Management depends on your symptoms, the mass’s size and location, your age, and your fertility goals.

  • Observation or Medication: Small, asymptomatic masses might just be monitored. Medications can sometimes be used to manage heavy bleeding.
  • Office Biopsy: To evaluate abnormal bleeding, a doctor might perform a simple office endometrial biopsy. While this is helpful for assessing the overall health of the uterine lining and checking for cancer, a blind biopsy can miss a small, focal mass like a polyp [8][19].
  • Hysteroscopy: For lesions inside the uterine cavity (polyps and submucosal fibroids), a hysteroscopy is often recommended [8][19]. A thin camera is inserted through the cervix, allowing the doctor to see the mass and remove it (a polypectomy for polyps, or myomectomy for fibroids). Medical guidelines note that hysteroscopy is much more accurate than a blind D&C (dilation and curettage, a procedure to scrape the uterine lining) for finding and removing these focal masses [8][20]. Hysteroscopic removal can resolve bleeding and may improve fertility outcomes for submucosal lesions [21][8][7].
  • Other Fibroid Treatments: Fibroids deeper in the muscle wall (intramural or subserosal) cannot be treated with hysteroscopy and may require other approaches, such as laparoscopic surgery, uterine artery embolization, or a hysterectomy [3].

Common questions in this guide

How are a uterine polyp and a fibroid different?
A uterine polyp is an overgrowth of the endometrium, the lining inside the uterus. A fibroid, also called a leiomyoma, is a benign growth made of smooth muscle in the uterine wall. A polyp projects into the uterine cavity, while fibroids may grow into the cavity, within the wall, or outward from the uterus.
Do polyps and fibroids cause different bleeding symptoms?
Polyps are more often linked with spotting or bleeding between periods, whereas fibroids commonly cause heavy or prolonged menstrual bleeding. Symptoms overlap, so bleeding pattern alone cannot confirm which growth is present.
Can an ultrasound tell whether a uterine mass is a polyp or fibroid?
A transvaginal ultrasound can find a uterine mass, but a submucosal fibroid can look like a polyp. Doppler blood-flow patterns and saline-infusion sonohysterography may provide more clues, while tissue examined under a microscope is the definitive way to confirm the diagnosis.
Can a uterine polyp or fibroid affect fertility?
Yes, both may make it harder to conceive or maintain a pregnancy, although many people with either condition become pregnant normally. Polyps and fibroids that bulge into the uterine cavity, especially submucosal fibroids, can interfere with embryo implantation; intramural and subserosal fibroids generally have less effect.
Does a uterine polyp or fibroid always need to be removed?
No. Small masses without symptoms may be monitored, while treatment depends on bleeding, size, location, age, and fertility goals. Hysteroscopy can directly remove a polyp or a fibroid inside the cavity; fibroids deeper in the uterine wall may need another treatment or no treatment.
Could a uterine polyp or fibroid be cancerous?
Most polyps and fibroids are benign. In broad studies, about 2.7% of polyps contained precancerous or cancerous cells, with higher risk after menopause or with abnormal bleeding and obesity; fibroids are very rarely cancerous. Imaging cannot provide absolute certainty, so removed tissue may be examined by pathology.
When should bleeding from a uterine polyp or fibroid be checked urgently?
Seek urgent medical evaluation if bleeding quickly soaks through pads or occurs with dizziness, fainting, or shortness of breath. Any bleeding after menopause should also be assessed promptly, even if it is light.

Related questions

How Long to Avoid Sex After Hysteroscopic Polypectomy? Can a Uterine Polyp Cause Bleeding, Pain, or Discharge? Can a Small Endometrial Polyp Disappear Without Treatment? Can a Normal TV Ultrasound Miss an Endometrial Polyp? Can Tamoxifen or Hormone Therapy Cause Uterine Polyps?
Show more
When Is Bleeding From a Uterine Polyp an Emergency? Can a Uterine Polyp Cause Iron-Deficiency Anemia, Too? What Happens During an SIS Exam for a Uterine Polyp? Is Office Hysteroscopy Painful? Uterine Polyp Anesthesia Does a Thickened Endometrium Mean a Polyp on Ultrasound? Can a Normal Biopsy Miss a Uterine Polyp? Hysteroscopy Can a D&C Miss or Leave Behind an Endometrial Polyp? Can Uterine Polyps Be Prevented or Inherited? What to Know Does an Asymptomatic Uterine Polyp Need to Be Removed? How Common Are Uterine Polyps Before and After Menopause? Can a Pap Test Find an Endometrial or Uterine Polyp? Endometrial Polyp: Saline Ultrasound or Hysteroscopy? How Often Should an Asymptomatic Uterine Polyp Be Monitored? Do Obesity, Diabetes, or Hypertension Cause Uterine Polyps?

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References

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This comparison of uterine polyps and fibroids is for informational purposes only and does not constitute medical advice. A gynecologist or other qualified clinician should interpret your imaging, symptoms, and pathology and recommend care for your situation.