Incidental Thyroid Nodules on Computed Tomography: A Radiologist's Perspective

In this issue of Thyroid, Drake et al report that incidental thyroid nodules (ITNs) included in the impression section of a radiology report were >3.5 times more likely to undergo subsequent evaluation compared with nodules that were included only in the findings (body) section of the report. ¹ They also found that the thyroid cancer diagnosis rate and survival outcomes were not significantly different between groups. These results highlight several important issues regarding ITNs including the impact of radiology reporting, the low malignant potential of ITNs, and a consideration of best practices moving forward.

The findings section of a radiology report is a descriptive section that may contain observations from the radiologist regarding the images reviewed. The impression section is where radiologists interpret the findings into actionable statements and where they place answers to the clinical question for the imaging study. When radiologists encounter incidental findings such as ITNs, they decide whether the nodule should be reported in the findings section, and if it is, whether it should also be reported in the impression. These reporting decisions are not arbitrary but are in fact a core competency in radiology. To put it another way, radiologists are not just identifiers and recorders, rather, we are physicians with imaging expertise whose goal is to guide imaging-related care through appropriate and accurate transfer of information.

It is in this context that we are pleased that this study finds that ITNs are less likely to receive workup when not mentioned in the impression. The authors propose that, “Providers are less likely to be aware of incidentalomas only reported in the body of the report, and this approach has been suggested as a way to influence the ordering providers' evaluation decision.” As radiologists, we agree with the statement, but disagree with the authors' intention. It is in fact our job to influence providers' evaluation decision.

Without this critical guidance, unnecessary, costly, and anxiety-provoking workups would skyrocket. Referring clinicians cannot be expected to be experts on every incidental finding. That domain falls to the radiologist. In addition, we strongly disagree with, “This strategy, if true is a clear violation of patient autonomy, the right of patients to make decisions about their medical care.…” Patients should have autonomy, but they are not experts; patients do not have the same perspective as radiologists, who see hundreds of incidental findings in daily practice and who are trained in how to manage them.

To help facilitate appropriate care that radiologists provide, eight years ago the American College of Radiology (ACR) developed criteria for workup of ITNs. ² ITNs smaller than 1.5 cm in patients >35 years old do not require follow-up. Radiologists may include them in the body of the report for completeness, but evidence does not support follow-up ultrasonography for these nodules. ^3,4 While these guidelines were introduced during the study period and were likely not implemented for the study, some of the nodules included only in the findings sections were likely small nodules that did not warrant workup.

Moreover, radiologists who included nodules only in the findings section may have been exercising clinical judgment about the patient: for example, a patient with stage 4 lung cancer on computed tomography (CT) who has an ITN is unlikely to need a workup. This scenario is also reflected in the ACR guidelines, which recommend that patients with limited life expectancy do not undergo evaluation of their ITNs. While the data from this study show that ITNs left in the findings were less likely to receive workup, we believe that most nodules were likely appropriately left in the findings section. In fact, the physicians reading the reports may have even seen the nodule in the findings section and also judged that the nodule not reported in the impression should not receive workup based on small size and patient factors.

Despite ACR guidelines, radiologists can still improve. Radiology reporting of ITNs has been shown to be variable across radiology subspecialties, ⁵ and radiologists do not always report according to white paper guidelines. ⁶ Data from studies such as these demonstrate that adherence to guidelines can improve. Referring clinicians, however, can also improve, with one study reporting that ITNs for which follow-up was explicitly recommended received that workup in less than half of cases. ⁶ Results from this study may also support that claim, as only 48% of nodules in report impressions underwent workup (though we do not know whether nodules in the impression warranted workup nor do we know whether workup was recommended).

Data from this study add to the growing body of literature that ITNs are largely benign. Out of 1460 chest CTs with ITNs, cancer incidence was only 1.1%. Moreover, a strength of the article was the clinical follow-up, which showed no difference between nodules reported in impression or only in the body of the report in terms of in-cancer diagnoses, cancer-specific mortality, and all-cause mortality. Thus, the additional biopsies and thyroidectomies resulting from reporting ITNs in the impression did not improve health care outcomes.

We propose that best practice for ITN reporting includes adherence to the ACR white paper on ITNs. When ITNs do not meet criteria for follow-up, they can be included in the body of the report or can be omitted. We do not report nodules that are <10 mm. Radiologists can consider a statement in the findings section to reflect that follow-up is not needed: “Small bilateral thyroid nodules which do not meet ACR criteria for followup.” When nodules meet criteria for workup with dedicated ultrasonography, our practice is to state, “Although the nodule is most likely benign, it could be further evaluated with ultrasound.”

We thank Drake et al for their excellent article, which further supports the need to reduce unnecessary workup of thyroid nodules and shows the impact of how radiologists report findings. Radiologists are not just detectors of findings, but rather they interpret findings, provide guidance, and play a critical role in combating the epidemic of overdiagnosis in thyroid cancer, through appropriate reporting and follow-up recommendations.