Uterine fibroids can differ drastically in size. For some women, a fibroid can resemble the head of a pin. For others, fibroids can grow to the size of a melon. A common fear among women is the risk of these otherwise benign tumors becoming cancerous—especially when they grow rapidly in size.
Previous medical opinion linked rapidly growing fibroids to the risk of developing a cancerous tumor called uterine leiomyosarcoma or LMS. A 1994 study published in Obstetrics & Gynecology discredited this belief by showing that the risk of overall uterine cancer among women who underwent surgery for presumed fibroids was low at 0.23 percent.1 Of these women who reportedly had “rapidly growing fibroids,” the total risk of uterine cancer—specifically LMS—was only 0.27 percent.
Over a decade later, there’s still public concern regarding the risk of fibroid-related uterine cancer.
To address this concern, a team of researchers led by Dr. Elizabeth A. Pritts, MD, of Wisconsin Fertility Institute in Middletown, Wis., combed through thousands of scientific journals, narrowing down their search to 133 studies. Results published in Gynecological Surgery showed an estimated rate of LMS found at surgery for presumed benign fibroids to be approximately 1 in every 2000 women or 0.05 percent.2 Much less than previously thought.
Restricting their inclusion criteria further, Dr. Pritts and her team used a final 64 prospective studies and found an even lower risk of approximately 1 in 8300 cases or 0.012 percent. “Results suggest that the prevalence of occult LMS at surgery for presumed uterine fibroids is much less frequent than previously estimated,” Pritts and her team wrote. “This rate should be incorporated into both clinical practice and future research.”
These statistics are notably lower in comparison to previous risk rates calculated by the FDA, which hover around 2 per 1000 surgeries or 0.2 percent.2 These numbers give the medical community pause mainly because approximately 600,000 hysterectomies and nearly 40,000 myomectomies are performed annually in the US alone—many of which are done using laparoscopic power morcellation in order to avoid open surgery.3, 4 And according to the American Congress of Obstetricians and Gynecologists, the majority of hysterectomies—nearly 41 percent—are performed to treat symptomatic fibroids.5
Often used during what are considered “minimally invasive” surgeries, morcellation is a method of breaking up tissue into smaller pieces to help remove it laparoscopically or through smaller incisions. “When used for hysterectomy or myomectomy in women with uterine fibroids, laparoscopic power morcellation poses a risk of spreading unsuspected cancerous tissue, notably uterine sarcomas, beyond the uterus,” the FDA reported. “While the specific estimate of this risk may not be known with certainty, the FDA believes that the risk is higher than previously understood.”6
This leaves the public questioning the discrepancy between reported risks. Reviewing available literature is a widely accepted method of assessing medical risk—but it can be done in a number of different ways, leaving much open to interpretation.
According to Pritts, “While differences in methodology accounted for some of the difference in estimated rates, differences in the evidence base accounted for a much larger share.” In both investigations, researchers used their professional judgment to select specific search criteria, choose which studies to include or exclude, and determine which statistical test to use when analyzing collected data. All of these steps can be done differently and can result in higher or lower risk values.
What’s also unclear is how uterine LMS tumors develop. LMS could grow on its own or, albeit rare, arise from mutations found in preexisting fibroids. Genetic studies have shown that even though fibroids and LMS have different microRNA—a particle that regulates gene expression—genetic mutations found in fibroids can also be seen in LMS and may contribute to its development.7
Increasing age is another factor that can influence a woman’s risk of uterine cancer—including LMS. A study published last year in The Oncologist investigated over 2000 women who had undergone surgery for fibroid treatment.8 Results showed that women in their mid to late 70’s were five times more at risk of developing uterine cancer versus women younger than 30 years of age.
What’s also alarming is that uterine fibroids are exceedingly common—affecting up to 70 percent of white women and 90 percent of black women by age 50—and can present with similar symptoms associated with LMS, like abnormal vaginal bleeding, lower abdominal pain, and a pelvic or abdominal mass.9, 10 At this time, there still aren’t any reliable tests available that can predict if a woman with fibroids has uterine cancer until after these masses are surgically removed.
“While we have found that the prevalence of occult LMS is less than previously estimated, this does not negate the fact that such occult malignancies can and do occur,” concluded Pritts and her team. Since the exact change from benign fibroids to LMS isn’t understood and may happen suddenly or over time, women with fibroids are recommended to maintain regular check ups with their gynecologists.
ABOUT THE AUTHOR Alicia Armeli is a Health Freelance Writer, Registered Dietitian Nutritionist, and Certified Holistic Life Coach. She has master’s degrees in English Education and Nutrition. Through her writing, she empowers readers to live optimally by building awareness surrounding issues that impact health and wellbeing. In addition to writing, she enjoys singing, traveling abroad and volunteering in her community.
- Parker, W. H., Fu, Y. S., & Berek, J. S. (1994). Uterine sarcoma in patients operated on for presumed leiomyoma and rapidly growing leiomyoma. Obstetrics & Gynecology, 83(3): 414-418.
- Pritts, E. A., Vanness, D. J., Berek, J. S., Parker, W., Feinberg, R., Feinberg, J., & Olive, D. L. (2015). The prevalence of occult leiomyosarcoma at surgery for presumed uterine fibroids: a meta-analysis. Gynecological Surgery, 12(3): 165-177. doi: 10.1007/s10397-015-0894-4
- Centers for Disease Control and Prevention. (2016). Fact sheet: Hysterectomy in the United States, 2000–2004. Retrieved July 13, 2016, from http://www.cdc.gov/reproductivehealth/data_stats/
- National Uterine Fibroids Foundation. (2010). Statistics. Retrieved July 13, 2016, from http://www.nuff.org/health_statistics.htm
- The American Congress of Obstetricians and Gynecologists. (2011). Choosing the Route of Hysterectomy for Benign Disease. Retrieved July 13, 2016, from http://www.acog.org/Resources-And-Publications/Committee-Opinions/Committee-on-Gynecologic-Practice/Choosing-the-Route-of-Hysterectomy-for-Benign-Disease
- US Food and Drug Administration. (2014). UPDATED Laparoscopic Uterine Power Morcellation in Hysterectomy and Myomectomy: FDA Safety Communication. Retrieved July 13, 2016, from http://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/ucm424443.htm
- Verit, F. F., & Yucel, O. (2013). Endometriosis, leiomyoma and adenomyosis: the risk of gynecologic malignancy. Asian Pacific Journal of Cancer Prevention, 14(10): 5589-5597. doi: http://dx.doi.org/10.7314/APJCP.2013.14.10.5589
- Brohl, A. S., Li, L., Andikyan, V., Obican, S. G., Cioffi, A., Hao, K., Dudley, J. T., Ascher-Walsh, C., Kasarskis, A., & Maki, R. G. (2015). Age-stratified risk of unexpected uterine sarcoma following surgery for presumed benign leiomyoma. The Oncologist, 20(4): 433-439. doi: 10.1634/theoncologist.2014-0361
- US Department of Health and Human Services. (2013). How many people are affected by or at risk of uterine fibroids? Retrieved July 13, 2016, from https://www.nichd.nih.gov/health/topics/uterine/conditioninfo/Pages/people-affected.aspx
- Up To Date. (2016). Differentiating uterine leiomyomas (fibroids) from uterine sarcomas. Retrieved July 13, 2016, from http://www.uptodate.com/contents/differentiating-uterine-leiomyomas-fibroids-from-uterine-sarcomas