Simple Ovarian Cysts on Ultrasound Need No Further Monitoring

Fran Lowry

November 12, 2018

Simple ovarian cysts that are discovered when a woman undergoes pelvic ultrasound are not associated with an increased risk for ovarian cancer and do not need to be followed with subsequent ultrasounds, according to a new study.

However, if the ultrasound reveals a complex cyst or solid mass, then the risk for ovarian cancer is significantly elevated, and such cases require careful follow-up, the study concludes.

The study was published online November 12 in JAMA Internal Medicine.

Simple cysts are common, occurring in both pre- and postmenopausal women. They do not require imaging studies every 6 or 12 months, lead author Rebecca Smith-Bindman, MD, University of California, Berkeley, told Medscape Medical News.

"Unless these cysts are symptomatic, no additional surveillance or follow-up is needed. We are talking about findings that are present in a quarter of premenopausal women and 14% of postmenopausal women. They are incredibly common and should be considered normal," Smith-Bindman said.

It has long been known that these cysts are unlikely to develop into something serious, but the fear that they could harbor cancer, although the risk is small, has resulted in frequent surveillance of these lesions and referral to ob/gyns, she said. "There is no reason for this. This is an area where we are doing unnecessary surveillance."

We are doing unnecessary surveillance. Dr Rebecca Smith-Bindman

In the past, these cysts were often surgically resected, she said. Although surgery is not normally performed for them nowadays, imaging studies are often conducted every 6 to 12 months, causing much anxiety and extra healthcare costs.

"We used to take them out, so we're doing better than we used to — but they don't turn into cancer. This is not what cancer looks like, and it has just become an area where we are doing unnecessary imaging without any benefit," Smith-Bindman said.

Complex Cysts Significantly Heightened Risk for Ovarian Cancer

The nested case-control study included 72,093 women enrolled in Kaiser Permanente Washington who had undergone pelvic ultrasonography between January 1, 1997, and December 31, 2008. The majority of the women (approximately 75%) were younger than 50 years.

During this period, the women underwent 118,778 pelvic ultrasound examinations.

Most of the women had normal ovaries.

The most common ovarian finding other than a normal ovary was a simple cyst, which occurred in 12,957 women (24%) younger than 50 years and in 2349 women (13%) older than 50.

The researchers determined how many cases of ovarian cancer had been diagnosed through December 31, 2011, for which there was a minimum of 3 years of follow-up (range, 3 to 14 years) after the last ultrasonography during which a cancer could be diagnosed.

They found that 210 women were subsequently diagnosed as having ovarian cancer. Of these women, 49 were younger than 50 years, and 161 were 50 years or older.

Six different histologic subtypes of ovarian cancer occurred: papillary serous cyst-adenocarcinoma (36.6%), endometrioid carcinoma (12.0%), serous cystadenocarcinoma (10.6%), clear cell adenocarcinoma (8.5%), adenocarcinoma not otherwise specified (8.0%), and mucinous adenocarcinoma (4.9%), and other (2%).

The cancers were diagnosed a mean of 3.4 months (range, 0 to 35.5 months) after the first ultrasound.

The risk for cancer was significantly elevated in women with complex cysts or solid masses.

The risk of developing cancer was approximately zero in women with a simple cyst, regardless of its size.

In contrast, women with complex cystic masses were eight to 74 times more likely to develop ovarian cancer; the 3-year risk for cancer ranged from 9 to 430 cases per 1000.

None of the women in the younger age group went on to develop cancer.

In the older cohort, one woman did develop cancer in the follow-up period. "Her ultransonography had been obtained because of severe pain that demonstrated a 1-cm simple cyst. This patient had persistent, severe pain, and a CT scan performed 30 days after the first ultrasound diagnosed extensive peritoneal metastatic disease, which was presumed to be ovarian in origin," Smith-Bindman said.

A Simple Cyst Is Benign, but "What If"?

Writing in an invited commentary, Deborah Levine, MD, Beth Israel Deaconness Medical Center, Boston, notes that "the key point in the study...that simple adnexal cysts are unlikely to harbor malignancy, is well demonstrated."

However, crucial factors in the decision to not follow a cyst are the quality of the sonogram and possibly the size of the cyst, she writes.

"I agree with the sentiment that a simple cyst is basically a benign finding," Levine told Medscape Medical News.

"But sometimes there can be errors in the way that the ultrasound is interpreted or technically performed, and you could miss something in what is otherwise termed a simple cyst, and that is really why people want to follow these, so that they don't miss anything," she said.

"This was a well-done study, and I know it's a lot of work to do what these authors did. But it's only one study, and it would be very hard to change clinical practice based on one study. However, we are moving in that direction," Levine said.

"We're slowly changing the bar of which cyst do we need to follow. Everyone agrees that a real simple cyst is not going to be the kind of cyst that is associated with a bad acting cancer. But the question is, if you stop following everything that's a simple cyst, are you going to miss anything? I don't think we are quite ready to make that decision yet, but we are in the process of that, we are moving towards that," she said.

"But in the US, the medical legal environment is such that everybody is scared about missing a cancer. So, it's really hard to say you never need to follow anything," she said.

Everybody is scared about missing a cancer. Dr Deborah Levine

In her editorial, Levine writes that to make a "confident" diagnosis of a simple cyst, the quality of the sonographic examination is crucial.

"In the best of all possible worlds, everybody would have the best equipment, every patient would be easy to scan, and all doctors would be really great at interpreting ultrasounds. There is an art to ultrasound, and when you go back and look at a lot of the old literature, it's clear that some things that were being called simple cysts were not. So mistakes happen, and that is one of the issues," she said.

The current guidelines, published in 2010 in Radiology, note that there was little evidence in the literature to guide which asymptomatic simple cysts could be ignored and which need to be followed. They recommend yearly follow-up until the practitioner decides that the cyst is stable or is decreasing in size.

"We are in the process of revising that guideline to more strongly say that you don't need to follow these until they're greater than 3 cm, but that revision isn't out there yet. But where to set that line? That is where we are right now," Levine commented.

The study was sponsored by the National Institutes of Health. Dr Smith-Bindman and Dr Levine report no relevant financial relationships.

JAMA Intern Med. Published online November 12, 2018. Abstract, Commentary

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