Can a Fibroid Actually Be Uterine Leiomyosarcoma? What Patients Need to Know
- Deborah Ann Martin
- 1 day ago
- 9 min read
Fibroid or Uterine Leiomyosarcoma? Why Some Dangerous Tumors Are Hard to Recognize Before Surgery
When doctors originally found the large mass in my uterus, I was told it was a fibroid.
That diagnosis made sense.
Fibroids are common. Uterine leiomyosarcoma is rare.
My pathology after the hysterectomy was also reported as benign, so I believed I could finally put the fear of cancer behind me.
About a year and a half later, doctors found three large tumors in my abdomen and another tumor on my back. A biopsy ultimately showed uterine leiomyosarcoma.
I was left with questions I still cannot fully answer.
Was the original mass really only a fibroid?
Was cancer hidden within tissue that had looked benign?
Could the cancer have been present but impossible to identify before surgery?
Did morcellation contribute to the spread?
Some of those questions may never have complete answers.
But there is an important question I can help another woman understand:
Can a mass that looks like a fibroid actually be uterine leiomyosarcoma?
Fibroids Are Common and Usually Benign
Uterine fibroids, also called leiomyomas or myomas, are noncancerous growths that develop from uterine muscle tissue.
They can vary greatly in size and number.
Some people have no symptoms. Others may experience:
Heavy menstrual bleeding
Longer periods
Pelvic pressure
Pelvic pain
Frequent urination
Constipation
Back pain
Pain during intercourse
Enlargement of the abdomen
Fertility or pregnancy problems
Fibroids are not cancer, and they almost never transform into cancer. They are also not generally considered to increase the risk of other uterine cancers.
That means patients should not assume that having a fibroid means they are likely to have uterine leiomyosarcoma.
Leiomyoma and Leiomyosarcoma Sound Similar
The names can be confusing.
A "leiomyoma" is a benign smooth-muscle tumor.
A "leiomyosarcoma" is a malignant smooth-muscle tumor.
Both may arise from the smooth muscle of the uterus, but they are not simply early and late versions of the same condition.
A typical fibroid is not considered a precancerous growth that is expected to turn into leiomyosarcoma.
The greater concern is that a mass believed to be a fibroid may occasionally be an unsuspected sarcoma from the beginning.
Why Can They Be Difficult to Tell Apart?
Fibroids and uterine leiomyosarcoma can produce overlapping symptoms.
Both may appear as uterine masses.
Both may cause pain, pressure, bleeding, or abdominal enlargement.
Imaging can provide valuable clues, but no currently available preoperative test can reliably rule out every uterine leiomyosarcoma. ACOG states that leiomyosarcoma cannot be reliably diagnosed before surgery.
That does not mean doctors have no way to evaluate risk.
It means that even a careful evaluation cannot provide absolute certainty in every case.
What Tests May Be Used?
Depending on the patient, doctors may use:
Pelvic examination
Transvaginal or abdominal ultrasound
MRI
CT imaging
Endometrial sampling
Laboratory tests
Review of symptoms and growth patterns
Surgery and pathology
These tests may help identify suspicious features or rule out other conditions.
However, uterine leiomyosarcoma develops in the muscular wall of the uterus. A sample taken from the uterine lining may miss a tumor that does not extend into that lining.
A normal Pap test also does not rule out uterine leiomyosarcoma. Pap tests primarily screen for cervical cellular changes, not cancers deep within uterine muscle.
Does Rapid Growth Prove Cancer?
Rapid growth does not prove that a uterine mass is leiomyosarcoma.
In fact, ACOG notes that uterine size and rapid growth are not reliable indicators of leiomyosarcoma.
That does not mean changes in a uterine mass should be ignored. A new, enlarging, or symptomatic mass deserves appropriate medical evaluation, particularly when other risk factors or concerning findings are present.
Growth alone, however, cannot diagnose cancer.
That is one reason this disease can be so difficult to identify before surgery.
Symptoms That Deserve Medical Attention
Most of these symptoms have causes other than cancer.
They should still be discussed with a healthcare professional:
Bleeding after menopause
Unusually heavy or changing menstrual bleeding
Bleeding between periods
Increasing pelvic or abdominal pain
Persistent pelvic pressure
A rapidly enlarging abdomen
A new or enlarging pelvic mass
Pain during intercourse
Unexplained bladder or bowel pressure
Symptoms that return after previous uterine surgery
New masses elsewhere in the body
The Symptom I Almost Talked Myself Out of Ignoring
My own warning symptom was very specific: pain during intercourse.
My Pap test and examination were normal.
It would have been easy to tell myself that everything was fine.
But the pain did not make sense to me.
So I asked for an ultrasound.
That ultrasound changed my life.
It led to the discovery of the mass that eventually became part of my cancer story.
I will always be grateful that I listened to my body when something didn't feel right.
That does not mean pain during intercourse means someone has uterine leiomyosarcoma. It usually has other explanations.
It means that persistent or unexplained symptoms deserve to be discussed with a healthcare professional.
Why Age and Menopause Matter
Fibroids often develop during the reproductive years and may shrink after menopause.
A new or enlarging uterine mass after menopause deserves careful evaluation.
The risk of unsuspected uterine malignancy also rises with age. That is one reason the FDA advises against laparoscopic power morcellation in women who are postmenopausal or older than 50.
This does not mean every postmenopausal uterine mass is cancer.
It means the risk-benefit calculation changes.
How Rare Is an Unexpected Leiomyosarcoma?
Uterine leiomyosarcoma is rare, but estimates of how often it is unexpectedly found during surgery for a presumed fibroid vary widely.
The FDA currently estimates that leiomyosarcoma may be present in approximately 1 in 495 to 1 in 1,100 women undergoing surgery for presumed uterine fibroids.
ACOG discusses a broader range of estimates and cites an AHRQ systematic review suggesting that an unexpected leiomyosarcoma may be found in 1 in 770 surgeries to fewer than 1 in 10,000 surgeries for presumed symptomatic leiomyomas.
Why are the numbers so different?
Because studies may include different:
Patient populations
Ages
Types of surgery
Definitions
Study designs
Time periods
Methods of estimating risk
The important point is not that one number is guaranteed to be correct for every woman.
The important point is that uterine leiomyosarcoma is rare, but it cannot always be reliably ruled out before surgery.
Why “Rare” Must Not Mean “Ignore It”
Doctors must balance two realities.
First, most uterine masses are benign fibroids.
Second, an unsuspected leiomyosarcoma can have devastating consequences if it is cut apart and spread.
Patients should not be frightened into believing every fibroid is cancer.
They should be told honestly that testing cannot provide perfect certainty before surgery.
Then they should be allowed to consider how the tissue will be removed.
Can Imaging Identify uLMS?
Ultrasound and MRI may reveal features that increase concern, but imaging findings can overlap.
A radiologist may evaluate:
Tumor borders
Areas of tissue breakdown
Internal bleeding
Blood flow
Signal patterns
Growth
Spread beyond the uterus
Other masses
A suspicious scan may lead to referral to a gynecologic oncologist.
A scan that appears compatible with a fibroid does not create a 100 percent guarantee.
That uncertainty is one reason I wrote a separate article explaining what morcellation is, what contained and uncontained morcellation mean, and the questions I wish I had known to ask before my hysterectomy.
Why Pathology Matters
Pathologists examine tissue under a microscope to determine what type of cells are present.
For uterine smooth-muscle tumors, they may evaluate features such as:
Abnormal cell appearance
Cell division activity
Tumor cell death
Tumor borders
Invasion
Other microscopic characteristics
Large tumors can contain different areas.
One part may look different from another.
That is one reason adequate sampling matters.
Rare or difficult cases may benefit from review by a pathologist with experience in gynecologic sarcoma.
Questions to Ask About Pathology
Ask:
Was the entire specimen sent to pathology?
Was the tissue removed intact or in fragments?
How extensively was it sampled?
Was the diagnosis reviewed by a gynecologic pathologist?
Would review at a sarcoma center be appropriate?
Can I obtain the complete pathology report?
Are the slides or tissue blocks still available?
Were any findings described as uncertain or atypical?
Should the original specimen be reviewed again after a later cancer diagnosis?
When cancer is later diagnosed after surgery for a presumed fibroid, patients may want to ask whether the original pathology should be reviewed again, particularly if the original specimen or pathology findings raise questions.
It may not answer every question, especially when tissue was fragmented or the available sample is limited.
Can Cancer Hide Inside a Fibroid?
Patients sometimes describe this as “a little bit of cancer hiding inside a fibroid”.
The actual pathology may be more complicated.
A patient may have:
A benign fibroid
A separate leiomyosarcoma
A malignant tumor that was mistaken for a fibroid
A tumor with uncertain or borderline features
More than one type of uterine growth
Another type of smooth-muscle tumor
The wording should come from expert pathology rather than assumption. The pathology report, not an assumption, is what determines the diagnosis. A diagnosis of leiomyosarcoma generally depends on examination of tissue by a pathologist.
In my own story, I can say that my original mass was diagnosed as a fibroid; it was morcellated without containment, pathology made a mistake, and I was later diagnosed with metastatic uterine leiomyosarcoma.
I can also say that I believe the morcellation contributed to the spread.
Unless the medical evidence proves the exact route of spread, I should not state every detail as certainty.
That does not weaken the warning.
The established risk of spreading an unsuspected malignancy is serious enough.
Should Every Fibroid Be Removed?
No.
Many fibroids do not require surgery.
Treatment depends on:
Symptoms
Size
Location
Number
Age
Fertility plans
Menopausal status
Growth
Anemia
Pain
Bladder or bowel effects
Patient preference
Concern for another diagnosis
Options may include:
Observation
Medication
Hormonal treatment
Procedures that reduce blood flow
Focused ultrasound or other specialized treatments
Myomectomy
Hysterectomy
Every option has benefits, limitations, and risks.
The purpose of this article is not to tell every patient to demand surgery.
It is to encourage careful evaluation and informed discussion.
When to Consider a Second Opinion
A second opinion may be especially valuable when:
You are postmenopausal with a new or enlarging mass
Imaging is unusual
The mass is growing
Symptoms are worsening
A surgeon recommends morcellation
The uterus cannot be removed intact through the planned route
A large or unusual tumor is present
Cancer cannot be reasonably excluded
You do not feel your questions were answered
You have already had a recurrence after surgery for a presumed fibroid
A gynecologic oncologist is trained to manage cancers involving the female reproductive system.
Seeing one does not mean you definitely have cancer.
It may help ensure that cancer risk is considered before surgery.
What I Wish Someone Had Told Me
I know now that most fibroids are benign.
I know that uterine leiomyosarcoma is rare.
I know that doctors have tools to evaluate uterine masses, but no preoperative test can reliably rule out every leiomyosarcoma.
I also know what it feels like to be told something is a fibroid, believe the pathology is benign, and later discover that cancer was present.
I cannot go back and change what happened to me.
But I can tell another woman:
Ask questions.
Ask what your imaging shows.
Ask whether anything about your age, symptoms, or medical history changes the risk.
Ask how the tissue will be removed.
Ask whether it will be removed intact.
Ask whether morcellation is being considered.
Ask whether a second opinion is appropriate.
You don't have to be afraid of every fibroid.
You just deserve to understand what is known, what is uncertain, and what your choices are before surgery.
Hope for Today
Most fibroids are benign.
Do not allow fear of a rare cancer to take over your life.
But do not allow the word “rare” to silence reasonable questions.
Pay attention to changes.
Request an explanation of your imaging.
Ask how the tissue will be removed.
Ask whether your age or symptoms change the risk.
Ask whether another specialist should review the case.
You do not need to diagnose yourself.
You need enough information to participate meaningfully in the decision.
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References
American College of Obstetricians and Gynecologists (ACOG) — Uterine Morcellation for Presumed Leiomyomas — https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2021/03/uterine-morcellation-for-presumed-leiomyomas
U.S. Food and Drug Administration (FDA) — Laparoscopic Power Morcellators — https://www.fda.gov/medical-devices/surgery-devices/laparoscopic-power-morcellators
National Cancer Institute (NCI) — Uterine Sarcoma Treatment (PDQ®) — https://www.cancer.gov/types/uterine/patient/uterine-sarcoma-treatment-pdq
National Cancer Institute (NCI) — Leiomyosarcoma — https://www.cancer.gov/pediatric-adult-rare-tumor/rare-tumors/rare-soft-tissue-tumors/leiomyosarcoma
Mayo Clinic — Uterine Fibroids: Symptoms and Causes — https://www.mayoclinic.org/diseases-conditions/uterine-fibroids/symptoms-causes/syc-20354288
Mayo Clinic — Uterine Fibroids: Diagnosis and Treatment — https://www.mayoclinic.org/diseases-conditions/uterine-fibroids/diagnosis-treatment/drc-20354294
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