By Rebecca Bowers

In the past two decades, more frequent use of transvaginal pelvic ultrasound has led to increased identification of ovarian masses. Although most masses are considered benign, guidance has recommended continued monitoring of simple cysts because of the poor prognosis for malignant ovarian cancer and the chance that cancer could be present in masses that appear benign. In a just-published study of more than 72,000 U.S. women, the results indicate that such surveillance of simple cysts may not be necessary.1

The researchers found that simple cysts (defined as cysts that are round or oval shaped, with a thin wall, and with anechoic fluid and through transmission) are normal and extremely common in women both pre- and postmenopause. The simple cysts are not associated with an increased risk of ovarian cancer. Unless symptoms are present, simple cysts can be ignored safely, states the research team, comprised of investigators from the University of California, San Francisco (UCSF) and Kaiser Permanente Washington.

“There’s a great deal of unnecessary medical surveillance that goes on for simple cysts,” notes lead author Rebecca Smith-Bindman, MD, a professor in the Department of Radiology and Biomedical Imaging at UCSF. She also is a professor in the departments of Epidemiology and Biostatistics, and Obstetrics, Gynecology and Reproductive Medicine, and is a member of the Philip R. Lee Institute for Health Policy Studies.

Simple cysts are almost universally benign, observes Smith-Bindman. Because there was concern that such cysts could contain a precursor to cancer, patients with these cysts underwent frequent surveillance and referrals to gynecologists and oncologists, she states. “Our study found that asymptomatic simple cysts of any size should be considered normal findings in women of any age and ignored,” said Smith-Bindman in a press statement.

Understand the Findings

To perform the study, researchers followed 72,093 women who underwent pelvic ultrasound exams through Kaiser Permanente Washington between January 1997 and December 2008. About three-quarters of the women were younger than 50 years of age. During the study period, participants underwent 118,778 pelvic ultrasound exams. Among the approximately 50,000 women younger than 50 years of age, about 24% were diagnosed with a simple cyst. None of these women were found to have developed cancer during follow-up. Among the remaining women 50 years of age and older, about 13% were diagnosed with a simple cyst. Just one of these women received a cancer diagnosis.

For women with a simple cyst, no matter the size, the risk of developing cancer was approximately zero, according to the investigators’ statistical analysis. A total of 210 cases of ovarian cancer were diagnosed in the study, almost all occurring in women with a complex cystic mass.1

The findings suggest that the probability of cancer predicted by ultrasound was accurate. The odds of cancer significantly increased in women who had complex cystic or solid ovarian masses.1

One of the reasons for surveilling simple cysts is the possibility that imaging may not be accurate or that it may miss complex features, notes Smith-Bindman, who is a member of the UCSF Helen Diller Family Comprehensive Cancer Center. “This was not supported by our data,” stated Smith-Bindman. “Cysts interpreted as being simple, even extremely large ones, were not associated with cancer.”

Weigh the Evidence

Appropriate interpretation of cystic ovarian structures noted with vaginal ultrasound is important, says Andrew Kaunitz, MD, interim chair of the Department of Obstetrics and Gynecology at the University of Florida College of Medicine-Jacksonville and medical director of UF Health Women’s Specialists Emerson.

In premenopausal women, simple cystic structures less than 3 cm should not be referred to as a cyst, says Kaunitz. Instead, the term “dominant follicle” should be used in this setting, he states.

An accompanying editorial to the research article points out that follow-up imaging is not required for simple cysts that are less than 5 cm in diameter in premenopausal women.2

Information issued by the “Choosing Wisely” campaign, founded by the American Board of Internal Medicine Foundation to help avoid unnecessary healthcare, asks clinicians not to recommend follow-up imaging for adnexal cysts that are clinically inconsequential. The recommendation says that in women of reproductive age, simple and hemorrhagic cysts are almost always physiologic, and that in postmenopausal women, small simple cysts commonly occur and are clinically inconsequential.3

“Ovarian cancer, while typically cystic, does not arise from these benign-appearing cysts,” the guidance states. “After a good quality ultrasonography in women of reproductive age, do not recommend follow-up for a classic corpus luteum or simple cyst < 5 cm in greatest diameter.”

The American College of Obstetricians and Gynecologists (ACOG) has issued similar information about assessing and managing adnexal cysts.4 The ACOG information says that simple cysts of up to 10 cm in diameter on transvaginal ultrasound are likely benign. They may be monitored safely with repeat imaging without surgery, including in postmenopausal women.


  1. Smith-Bindman R, Poder L, Johnson E, Miglioretti DL. Risk of malignant ovarian cancer based on ultrasonography findings in a large unselected population. JAMA Intern Med 2018; doi: 10.1001/jamainternmed.2018.5113. [Epub ahead of print].
  2. Levine D. Evaluating an asymp-tomatic adnexal cyst found on pelvic ultrasonography. JAMA Intern Med 2018; doi: 10.1001/jamainternmed.2018.5133. [Epub ahead of print].
  3. American Board of Internal Medicine. Choosing Wisely. American College of Radiology. Don’t recommend follow-up imaging for clinically inconsequential adnexal cysts. Available at: Accessed Dec. 19, 2018.
  4. American College of Obstetricians and Gynecologists’ Committee on Practice Bulletins — Gynecology. Practice bulletin no. 174: Evaluation and management of adnexal masses. Obstet Gynecol 2016;128:e210-e226.