Invited Commentary: Categorizing Adnexal Masses at US, CT, and MRI—the Radiologist's Not-Impossible Mission

See also the article by Wang et al in this issue.

Benign adnexal cysts in women are very common. Normal ovaries in both premenopausal and postmenopausal women often harbor nonneoplastic cysts; invariably, some of those nonneoplastic structures will become larger than other follicles, either as part of normal ovulation in premenopausal women or as part of a less universal and less understood but still common normal postmenopausal process (1). In premenopausal women, the dominant follicle that ovulates develops wall thickening, irregularity, and hyperemia when it transitions to the corpus luteum, occasionally enlarging owing to internal hemorrhage to form a hemorrhagic ovarian cyst. Other benign nonneoplastic cysts include endometriomas, hydrosalpinges, paraovarian and/or paratubal cysts, and peritoneal inclusion cysts. There is some evidence to suggest that some benign serous cystadenomas may also be nonneoplastic rather than true neoplasms (2). On top of all these nonneoplastic entities, benign ovarian neoplasms including truly neoplastic cystadenomas and dermoids are more common than malignancies.

Unfortunately, because ovarian cancers often have a cystic component, the identification of an adnexal cyst introduces challenges for radiologists making the observation and for providers taking care of patients in whom the observation is made. The presence of an adnexal cyst not recognized or reported as likely nonneoplastic can lead to unnecessary follow-up imaging. At one center, without use of any expert consensus guidelines, 15% of pelvic US studies had a recommendation for follow-up US (3). The presence of an adnexal cyst not recognized or reported as likely benign can lead to unnecessary surgery. In a study based on a comprehensive nationwide registry in the Netherlands, of 11 595 women undergoing surgical evaluation of an adnexal mass, 2482 (21%) had a benign serous cyst and 1718 (15%) had a functional cyst accounting for the intervention; almost certainly, most of these did not need surgery (4). At the other end of the spectrum, the presence of an adnexal cyst not recognized or reported as likely malignant is also a problem. It has now been clearly established that when an adnexal mass is a malignancy, patients who were not directed to a gynecologic oncologist for the initial surgery have worse outcomes (5).

Cue the “Mission: Impossible” music and play the tape for the assignment.

The radiologist's mission when observing an adnexal mass is to decide whether it falls into one of four categories: (a) very likely related to a nonneoplastic process, in which case it would not merit imaging follow-up; (b) almost certainly benign even if neoplastic, in which case the utility of imaging follow-up is to either gain further confidence in the assessment and/or characterize the growth rate of the mass; (c) not necessarily benign but low likelihood of malignancy, in which case further imaging characterization, imaging follow-up, or surgical intervention without regard for oncologic expertise would be appropriate; or (d) moderate or high likelihood of malignancy, in which case patient outcome is optimized by initial gynecologic oncology surgical intervention. The radiologist who only describes an adnexal observation without articulating a clear categorization or proposed method to achieve such categorization, reasoning that management of the mass is the ordering provider's problem, has failed the mission.

The Society of Radiologists in Ultrasound (SRU) 2019 consensus update on simple adnexal cysts, the 2020 American College of Radiology (ACR) Ovarian-Adnexal Reporting and Data System (O-RADS) US Risk Stratification and Management Consensus Guideline, and the 2020 ACR Incidental Findings Committee (IFC) white paper regarding adnexal findings at CT and MRI articulate algorithms to assist radiologists in this mission (6–8). In this issue of RadioGraphics, Wang et al (9) promote the awareness and adoption of these algorithms as they apply to benign-appearing incidental adnexal cysts. This effort merits praise since it helps to educate radiologists on this topic, with illustrative images showing examples of various nonneoplastic cysts (follicle, corpus luteum, simple cyst, hemorrhagic cyst, endometrioma, hydrosalpinx, and peritoneal inclusion cyst) and benign neoplasms (dermoid, cystadenoma, and sex cord stromal tumor). In two patients, Wang et al (9) demonstrate the potential impact of these recommendations toward reducing the number of follow-up studies or toward recognizing the impact of cine clips obtained during sonographic evaluation.

As with many RadioGraphics articles, review of the figures and captions alone will advance the reader's ability to execute the mission. Of course, reading the article text is also quite useful to review important background information on major outcome studies, the normal ovary, and the genesis and evolution of the SRU and ACR recommendations. While the rationale for the approach taken by each group in crafting specific recommendations is broached in this review, all radiologists who use the SRU and ACR recommendations would benefit by also carefully reading and digesting the excellent source articles to help better apply the principles.

In adapting their Radiological Society of North America education exhibit for a wider audience, Wang et al (9) have achieved their objective to promote awareness and understanding. The review could be more instructive in explaining how we “put it all together.” How do we reconcile what seem to be different size thresholds, follow-up intervals, requirements for characterization, and the role of expertise? The SRU and the ACR IFC both articulate a superior characterization pathway not found in the O-RADS. The SRU advocates that premenopausal 5–10-cm simple cysts without superior US characterization are optimally subsequently evaluated in 6–12 months, whereas the O-RADS advises that they should optimally be evaluated in 8–12 weeks. The SRU algorithm advises short-interval follow-up (in 6–12 weeks), second-opinion US, or MRI when an adnexal cyst of any size regardless of menopausal status is “likely simple but not satisfactorily characterized at US,” whereas the ACR IFC recommends that a simple-appearing cyst with limited assessment at CT or MRI not undergo further imaging when under 5 cm in a premenopausal patient or under 3 cm in a postmenopausal patient. These are not the only differences among the three sets of recommendations.

Completely “putting it all together” when guidance differs might seem like an impossible mission, but it is achieved by focusing on the core objective: decide to which of the four categories the adnexal mass belongs and which clinical scenario best fits the patient. By so doing, radiologists will be better able to reconcile and tailor recommendations to the specific situation. The 5.5-cm right ovarian simple cyst in a premenopausal woman is properly categorized as being almost certainly benign even if neoplastic. The radiologist who understands that the observation is incidental and asymptomatic and who benefits from superior characterization including cine clips is justified in not recommending any follow-up (SRU approach) because even if the cyst is a benign neoplasm, it may be indolent and never come to clinical attention. Alternatively, the O-RADS approach of 8–12-week follow-up fits best when further assurance is of demonstrable benefit (such as when the cyst engendered the US owing to palpability or symptoms or when the radiologist can only review still images). Finally, the radiologist who puts it all together and recognizes that the patient underwent imaging last month at which the right ovary had no cyst understands that this new right simple 5.5-cm cyst is certainly nonneoplastic (related to normal physiology) and specifically articulates in the report that the mass should not engender follow-up despite not having cine clips and despite what the SRU and O-RADS charts state, saving the patient from an unnecessary follow-up examination (1).

For adnexal findings, putting it all together to decrease unnecessary imaging or surgery means more than looking up size thresholds on charts. Putting it together means maximizing personal educational efforts to improve recognition of benign entities, including reading the review by Wang et al (9) and the articles by the SRU and ACR panels (6–8). Radiologists must go further in their personal education by actively tracking the outcome of patients with adnexal observations they have made, since hemorrhagic cysts, hydrosalpinges, peritoneal inclusions cysts, endometriomas, and dermoids can be very confusing (10), and the ability of radiologists to recognize these entities improves with validated experience. Putting it together means using and carefully reviewing cine clips at US to better characterize adnexal masses. Registered diagnostic medical sonographers often do an amazing job depicting findings with still images, but a cine clip enables the radiologist to have higher confidence and contribute to making relevant observations. Putting it together means understanding the role of short-interval follow-up (in a few weeks) when confusing but potentially physiologic observations are present, and understanding when short-interval follow-up is inappropriate because normal physiology cannot reasonably explain the suspicious observations (1). Putting it together means taking the time and effort to get a second opinion from a colleague who may offer helpful observations, rather than dictating an unhelpful report simply to get the study off the list as quickly as possible. Ultimately, putting it together means getting better at categorizing adnexal observations into one of four categories, understanding how those categories dictate recommendations, and recognizing which guidance best fits the specific situation.

For adnexal masses, putting it together is the radiologist's mission: it is not impossible, we have no choice but to accept it, and this message will not self-destruct in 5 seconds.

Disclosures of Conflicts of Interest.— M.D.P. Royalties for a chapter from UpToDate, member of the SRU Consensus Panel on Simple Adnexal Cysts, and Chair of the ACR Adnexal Mass IFC.