Incidental Thyroid Nodules on CT or MRI: Discordance Between What We Report and What Receives Workup

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1 Neuroradiology/Head and Neck Imaging Original Research Tanpitukpongse et al. Reporting and Workup of Incidental Thyroid Nodules Noted on CT or MRI Neuroradiology/Head and Neck Imaging Original Research Teerath P. Tanpitukpongse 1 Allen T. Grady 1 Julie A. Sosa 2 James D. Eastwood 1 Kingshuk R. Choudhury 1 Jenny K. Hoang 1,3 Tanpitukpongse TP, Grady AT, Sosa JA, Eastwood JD, Choudhury KR, Hoang JK Keywords: CT, incidental, MRI, nodule, thyroid DOI: /AJR Received May 4, 2015; accepted after revision July 10, Department of Radiology, Duke University Medical Center, Box 3808, Erwin Rd, Durham, NC Address correspondence to J. K. Hoang (jennykh@gmail.com). 2 Department of Surgery, Duke University Medical Center, Durham, NC. 3 Department of Radiation Oncology, Duke University Medical Center, Durham, NC. AJR 2015; 205: X/15/ American Roentgen Ray Society Incidental Thyroid Nodules on CT or MRI: Discordance Between What We Report and What Receives Workup OBJECTIVE. The objective of this study was to determine the proportion of incidental thyroid nodules (ITNs) reported on CT or MRI that receive additional workup and the factors that influence workup. A secondary aim was to evaluate the effect of the American College of Radiology () white paper recommendations for reporting of ITNs. MATERIALS AND METHODS. We retrospectively reviewed patients with ITNs reported on CT or MRI studies over 12 months. We identified patients with ITNs that underwent workup and the factors associated with workup. The white paper recommendations were retrospectively applied to estimate how their use would have changed the number of nodules reported in the impression section of radiology reports and the number of cancers diagnosed. The recommendations are based on suspicious imaging features, patient age, and nodule size. RESULTS. A total of 375 patients had ITNs reported. For 138 of these patients (37%), ITNs were reported by radiologists in the impression section of their reports; 26 patients (19%) received workup. Patients with ITNs reported in the impression section were 14 times more likely to undergo workup than were patients with ITNs reported only in the findings section of the radiology report. On multivariate analysis, the only factors associated with workup were younger patient age and larger nodule size (p 0.002). The recommendations resulted in a 54% reduction in the number of ITNs reported in the impression section and one missed papillary cancer (TNM classification T1bN0M0). CONCLUSION. Only one in five patients with ITNs reported in the impression section of CT or MRI reports underwent additional workup, and this decision was influenced by younger patient age and larger nodule size. These factors are components of the recommendations, which have the potential to reduce the number of reported ITNs and improve the standardization of radiology reporting. I ncidental thyroid nodules (ITNs) are common and are seen on CT or MRI in up to 16 18% of imaging studies that include the neck [1, 2]. There are no specific imaging findings to indicate a malignant nodule on CT or MRI, so ultrasound is the next best method for additional evaluation [3, 4]. Without guidelines for the radiologist on how to report ITNs detected on CT or MRI, there are highly variable reporting practices [5, 6]. Clinicians could be guided by the American Thyroid Association, but this organization states that all ITNs detected on CT or MRI should undergo an ultrasound workup [7]. This approach may not be cost effective because most ITNs are benign and because treatment of small thyroid cancers may not change survival outcome [8 10]. In addition, the decision to investigate all ITNs could frequently lead to biopsy and surgery for nodules that are benign and clinically insignificant [10 13]. Despite the recommendations of the American Thyroid Association to perform an ultrasound evaluation of any ITNs, two previous studies have shown that most ITNs reported on CT or MRI do not routinely undergo subsequent evaluation. Yousem et al. [1] found that only 16% of patients with ITNs underwent additional workup, whereas Nguyen et al. [2] found that only 36% of such patients underwent subsequent evaluation. Given that there is discordance between the number of patients who have ITNs reported and the number of patients who actually undergo additional workup, it is valuable to study the characteristics of patients AJR:205, December

2 Tanpitukpongse et al. with ITNs who undergo workup and to identify the factors that are associated with workup, such as reporting styles and patient- and nodule-associated characteristics. Information about which ITNs undergo subsequent evaluation can help radiologists understand the clinical significance of ITNs seen on CT or MRI. Guidelines for evaluating ITNs detected on CT or MRI ultimately should aim to reduce the workup of benign ITNs and should identify malignant ITNs at a clinically significant stage [14]. In a recent white paper, the American College of Radiology () proposed recommendations for guiding the evaluation of ITNs [15]. These recommendations were based on the three-tiered system used at Duke University Medical Center, which selects patients on the basis of the following criteria: patient age, nodule size, and suspicious imaging findings [2, 4, 13]. Three retrospective studies found that the three-tiered system had the potential to reduce radiographic and endocrinologic workup without overlooking advanced malignancies in the respective patient cohorts [2, 13, 16]. Thus, it is of interest whether the white paper recommendations could reduce the number of ITNs emphasized in the impression section of the radiology report and whether reducing the number of nodules reported would lead to missed malignancies. The purpose of this study was to measure the proportion of reported ITNs observed on CT or MRI that subsequently underwent focused evaluation and to determine the factors associated with the decision to perform this evaluation. A secondary aim was to evaluate the effect of the white paper recommendations for reporting ITNs. Our hypothesis was that a small proportion of ITNs undergo subsequent workup and that certain factors related to the demographic characteristics of the patient and the imaging characteristics of the nodule influence workup. We also hypothesized that adopting the white paper recommendations could result in a reduction in the number of ITNs reported by radiologists without clinically significant cancers being missed. Materials and Methods Study Population We retrospectively studied 401 patients with thyroid nodules reported on CT or MRI studies between January 1, 2011, and December 31, This period was selected because it was before implementation of both the three-tiered system and the white paper recommendations at our institution. The three-tiered system is a reporting system for ITNs detected on CT, MRI, or PET. The initial intent at the time of conception of this study was to evaluate the three-tiered system, but by the time we submitted this article for publication, the white paper recommendations had been published. The white paper recommendations for ITNs detected on CT or MRI are the same as the recommendations of the three-tiered system. Patients were identified by performing a text search for the phrase thyroid nodule in CT or MRI reports. PET/CT reports were not included in the text search. To obtain a cohort limited to patients with ITNs, a patient was excluded if the imaging study was performed to evaluate symptoms or signs related to the thyroid gland or if the patient had a history of thyroid disease or had undergone prior evaluation of the thyroid gland, such as a previous thyroid ultrasound study or thyroid biopsy. The institutional review board at our institution approved the study. Written informed consent was waived. All data were collected by two radiologists, each of whom had 4 years of experience. Style of Incidental Thyroid Nodule Reporting and Subsequent Workup All patients had formal radiology reports issued by board-certified radiologists in the subspecialties of neuroradiology or abdominal, cardiothoracic, or musculoskeletal imaging. During the study, there were no formal institutional guidelines for reporting ITNs on CT or MRI. The two radiologists categorized the radiology reports into two groups. The first group of reports included mentions of ITNs in the impression section of the report rather than in only the body or results section of the report. The second group reported ITNs for which subsequent evaluation was recommended versus ITNs for which there was no recommendation for further diagnostic evaluation. The medical records were reviewed for patients who underwent workup. The minimal follow-up was 3 years were reviewed. ITN workup could comprise any one of, or a combination of, the following studies or procedures: thyroid ultrasound, fine-needle aspiration (FNA), or thyroid surgery. The outcomes of workup included cytopathologic analysis, for patients who underwent FNA and histologic analysis for patients who underwent surgical resection. Cytopathologic findings were categorized according to the Bethesda system [17]. Patients who underwent ultrasound without an associated biopsy were assumed to have benign ITNs. Outpatient encounters after the CT or MRI study were also recorded to estimate the number of patients who might have been lost to follow-up. Factors Associated With Workup Data on factors that could influence subsequent evaluation of the ITN were collected from radiology reports and medical records. These factors were categorized as patient and nodular characteristics. Patient characteristics included age, sex, and the indication for the imaging study. The nodular characteristics of interest were nodule size, morphologic findings (macrocalcification, cystic components, or hypervascularity), and the presence of suspicious lymph node involvement. Medical records also were reviewed for information on the subspecialty of the radiologist who reported the study and the subspecialty of the physician who ordered the study. Effect of the American College of Radiology White Paper Recommendations on Reporting and Workup The white paper recommendations were applied retrospectively to estimate how the application of consistent guidelines could change the number of nodules reported in the impression section of the radiology report and the number of nodules that would undergo workup. The white paper recommendations are based on suspicious imaging features, patient age, and nodule size [15]. Patients with active metastatic disease associated with a known malignancy were excluded because the white paper does not recommend workup for patients with limited life expectancy. In addition, application of the white paper recommendations required knowledge of nodule size, so patients for whom nodule size was not reported were also excluded. A nodule was considered to be positive (i.e., meet the criteria of the white paper recommendations) if criteria for inclusion in any of three categories were met [15]. Category 1 (denoting highest risk) included patients with nodules of any size and findings of concern, such as local invasion, suspicious lymph nodes, or distant metastases. Category 2 included patients younger than 35 years who did not meet the criteria for inclusion in category 1. Adults ( 18 years old) with a nodule 10 mm or larger and patients younger than 18 years with a nodule of any size met the criteria for workup. This group of patients was selected because young patients have a higher ratio of malignant to benign nodules [3, 18 22]. Category 3 included any patient 35 years old or older who had a nodule 15 mm or larger and who did not meet criteria for inclusion in category 1. This size cutoff has been used by several groups for ultrasound evaluation of thyroid nodules [14, 23]. Patients who met criteria for inclusion in any of the three categories were patients with an ITN that should have been reported in the impression 1282 AJR:205, December 2015

3 Reporting and Workup of Incidental Thyroid Nodules Noted on CT or MRI section of the report according to the white paper recommendations. Outcome Measures and Statistical Analysis The primary outcome of interest was the proportion of ITNs that underwent workup after they were reported in the impression section of the radiology report. The characteristics of patients with ITNs that underwent subsequent evaluation were compared with the characteristics of patients with ITNs that did not undergo additional workup. Either a chi-square test or Fisher exact test was used to test differences in categoric variables between patients with ITNs that underwent workup and patients with ITNs that did not undergo workup. The unpaired t test was used to test for differences in continuous variables. A multivariable logistic regression model was fitted to identify factors that were associated with the decision to perform additional workup of ITNs. We estimated the potential reduction in the number of ITNs that would be reported in the impression section of the radiology report if negative (n = 48) ITN reported only in findings (n = 56) white paper recommendations were followed. This estimation was calculated as the difference between the number of -negative ITNs (i.e., ITNs that did not meet white paper recommendations) reported in the impression section and the number of -positive ITNs not reported in the impression section, divided by the total number of ITNs reported in the impression section. We also measured the potential reduction in the number of ITNs that underwent FNA, surgery, or both when white paper recommendations were followed, and we determined whether any cancers would be missed. The data were entered into an Excel spreadsheet (2007 version, Microsoft). Statistical analyses were performed using SAS Enterprise software (version 4.2, SAS Institute). A p value of less than 0.05 was considered to be statistically significant. Results Study Population A total of 375 of 401 patients with ITNs reported by radiologists on CT or MRI met Patients with reported thyroid nodules (n = 401) Patients excluded: 1. Study indication of goiter (n = 4) 2. Prior 131 I therapy for hyperthyroidism (n = 1) positive (n = 8) Additional nodules that would have been reported in impression section Patients with ITNs (n = 375) -eligible patients (n = 147) negative (n = 57) Nodules that would not have been reported in impression section 3. Risk factors for thyroid cancer (n = 1) 4. Prior thyroid ultrasound, FNA, or surgery (n = 20) Patients excluded: 1. Nodule size not reported (n = 175) 2. Known malignancy with active metastatic disease (n = 20) ITN reported in impression section (n = 91) positive (n = 34) Fig. 1 Flowchart of study inclusion criteria used to select patient population. FNA = fine-needle aspiration, ITN = incidental thyroid nodule, = American College of Radiology. the inclusion criteria (Table 1 and Fig. 1). The mean size of the thyroid nodule reported in any part of the radiology report (either in the findings section or the impression section) was 15 mm (SD, 9 mm). Incidental Thyroid Nodules That Were Reported in the Impression Section and Received Workup A total of 138 of 375 ITNs (37%) were reported in the impression section of the radiology reports (with the remainder reported in the findings section only), and 26 (19%) of these ITNs underwent subsequent workup. Workup was also performed in four patients who had ITNs reported only in the findings section of the radiology report. A total of 69 of 375 ITNs (18%) were reported along with specific recommendations that additional workup be performed; of these, 18 (26%) had workup done at our institution. Nodules that were reported in the impression section of the report or were recommended for additional evaluation were more likely to receive workup (p < ). The odds ratio (OR) for workup if the nodule was reported in the impression section rather than in the findings section only was 14 (95% CI, 5 40), which was higher than the OR for nodules recommended for workup compared with those not recommended for workup (OR, 9 [95% CI, 4 19]). Of the 30 patients with reported ITNs who underwent subsequent evaluation, 24 (80%) underwent ultrasound, 21 (70%) had FNA performed, and two (7%) proceeded to surgery. The potential rate of patients who were lost to follow-up and who received followup at an outside institution was at least 9%, because 33 of 375 patients did not have any subsequent outpatient visits at our institution after the original CT or MRI examinations. Of the 21 patients who underwent biopsy or surgery, two (10%) had thyroid malignancy (Table 2). The overall malignancy rate was 6% among the 30 patients who received workup and 0.5% among the 375 patients with ITNs. None of the patients who had ultrasound performed without biopsy had malignancy develop during follow-up. One of the two patients with a thyroid malignancy was a 67-year-old man with stage IVc anaplastic thyroid cancer who underwent CT examination of the chest for evaluation of pulmonary nodules (unknown primary tumor) seen on a chest radiograph. Although he did not have neck symptoms, he had a 5.6-cm left thyroid mass and multiple other smaller thyroid AJR:205, December

4 Tanpitukpongse et al. TABLE 1: Characteristics of Incidental Thyroid Nodules Reported on CT and MRI Studies Characteristic All Nodules (n = 375) Ultrasound (n = 24) Fine-Needle Aspiration (n = 21) Surgery (n = 2) Any Workup (n = 30) No Workup (n = 345) Univariate p a Multivariate p a Patient characteristic Age (y), mean ± SD 64 ± ± ± ± 9 59 ± ± Female, no. (%) of patients 250 (67) 18 (75) 19 (91) 2 (100) 23 (77) 220 (64) 0.23 Indication for study < > 0.16 Malignancy 196 (52) 5 (21) 4 (19) 0 6 (20) 190 (55) Vascular 63 (17) 5 (21) 5 (24) 0 8 (27) 55 (16) Trauma 43 (11) 1 (5) 1 (5) 0 1 (3) 42 (11) Infection, inflammation, 24 (6) 6 (25) 3 (14) 0 6 (20) 18 (5) or both Other 49 (13) 7 (29) 8 (38) 2 (100) 9 (30) 40 (12) Nodule characteristic Size (mm), mean ± SD b 15 ± 9 17 ± ± ± ± ± 8 Size, no (%) of patients c < 10 mm, subcentimeter 75 (20) 6 (25) 4 (19) 1 (50) 7 (23) 68 (20) mm 52 (14) 6 (25) 6 (29) 0 7 (23) 45 (13) mm 26 (7) 3 (13) 3 (14) 0 4 (13) 22 (6) > 20 mm 47 (13) 9 (38) 8 (38) 1 (50) 12 (40) 35 (10) Morphologic characteristic, 0.87 no. (%) of patients Calcifications 63 (17) 4 (17) 5 (24) 1 (50) 6 (20) 57 (17) Cystic components 4 (1) (1) Hypervascularity 2 (1) (1) Division of radiologist > 0.05 Chest imaging 92 (25) 10 (42) 11 (52) 1 (50) 14 (47) 78 (23) Neuroradiology 103 (27) 11 (46) 7 (33) 1 (50) 11 (37) 92 (27) Body imaging 172 (46) 3 (13) 3 (14) 0 5 (17) 167 (48) Musculoskeletal imaging 8 (2) (2) Subspecialty of referring 0.96 clinician, no. (%) of patients Emergency medicine 42 (11) 3 (13) 2 (10) 0 (0) 3 (10) 39 (11) Medicine 238 (63) 15 (63) 13 (62) 2 (100) 19 (63) 219 (63) Surgery 86 (23) 6 (25) 6 (29) 0 (0) 8 (27) 78 (23) Family medicine and other 9 (2) 0 (0) 0 (0) 0 (0) 0 (0) 9 (3) Reporting style, no. (%) of patients Reported in impression 138 (37) 21 (88) 18 (86) 2 (100) 26 (87) 112 (32) < section of report Ultrasound recommended 69 (18) 16 (67) 11 (52) 1 (50) 18 (60) 51 (15) < a Derived from comparison of incidental thyroid nodules that received workup compared with those that did not. b Only nodules with numeric values were included. c Not all patients had nodule size included in the radiology report. The nodules were measured on the CT or MR images for cases that had workup with missing nodule sizes to categorize nodules by the three-tiered system. nodules. The patient s nodule was reported in the impression section of the radiology report as most likely representing multinodular goiter. Workup was not recommended for this patient. The second patient with a thyroid malignancy was a 47-year-old woman with T1bN0M0 papillary cancer who underwent chest CT for evaluation of possible sarcoidosis. CT revealed a 9-mm coarsely calcified nodule. The ITN was reported in the impression section of the report, with no recommendation for workup AJR:205, December 2015

5 Reporting and Workup of Incidental Thyroid Nodules Noted on CT or MRI For the 19 other patients who underwent biopsy or surgery, the Bethesda system categories included 16 category II benign nodules (76%); two category III atypia of undetermined significance or follicular lesion of undetermined significance (10%); and one category IV follicular neoplasm (5%) (Table 2). Factors Associated With Workup Table 1 shows that the factors associated with workup on univariate analysis were patient age, indication for the imaging study, nodule size, radiology division reporting the study, and reporting style (p 0.04). Patients who received workup were younger (mean age, 59 years) than patients who did not undergo evaluation (mean age, 64 years). The mean nodule size of patients receiving workup was 18 mm, which was larger than the mean nodule size (14 mm) of patients who did not undergo evaluation. Patients who underwent scanning for evaluation of a known malignancy were less likely to undergo subsequent evaluation of their ITNs. Lower workup rates were also seen for patients with ITNs reported by the abdominal imaging division (Table 1). The subspecialty of the referring clinician was not associated with workup. Only five patients were referred by the otolaryngology head and neck surgery division. On multivariate analysis, the only factors significantly associated with ITNs undergoing additional evaluation were patient age (p = 0.002) and nodule size (p = ) (Table 1). Effect of American College of Radiology White Paper Recommendations on Reporting and Workup The white paper recommendations could be applied retrospectively to 147 nodules after the exclusion of 175 nodules for which no size was reported and 53 patients with active metastatic disease in the setting of a known malignancy (Fig. 1). A total of 42 ITNs (29%) were positive (one in category 1, zero in category 2, and 41 in category 3) and met the criteria of being reported in the impression section of the report. The 105 remaining ITNs were negative and would be reported only in the body of the report or not at all. Of the 147 ITNs that were categorized on the basis of white paper recommendations, 91 ITNs (62%) were reported in the impression section. If the white paper recommendations had been adopted for reporting in this period, 57 ITNs would not have been reported in the impression section ( negative), and eight ITNs would have been reported in the impression section rather than in the body of the report ( positive) (Fig. 1). This represents a net reduction of 54% (49/91) in the number of ITNs reported in the impression section of the report. The white paper recommendations were applied to the 21 ITNs that underwent FNA, surgery, or both (Table 3). Of the 10 patients whose ITNs were negative and may have not have received workup (48%), one patient had T1bN0M0 papillary cancer. Discussion There is discordance between ITNs observed on CT or MRI scans and reported by radiologists and ITNs that actually receive workup by clinicians [1, 2]. This study found that only a small proportion of nodules reported on CT or MRI underwent subsequent evaluation, and the clinician s decision to perform additional testing for selected ITNs appeared to be influenced by patient age and nodule size. Patient age and nodule size are components of the white paper recommendations, and using this categorization method could halve the number of ITNs reported in the impression section of imaging reports by radiologists. The impression section of a radiology report serves to summarize and interpret clinically significant findings and provide recommendations. In our study, 37% of ITNs were reported in the impression section of the report, suggesting that the radiologists regarded them to be significant findings. However, less than a fifth of these nodules underwent subsequent evaluation directed by clinicians. This workup rate is similar to the 16 36% workup rate noted in previous studies of ITNs seen on CT or MRI [1, 2]. The low workup rate relative to the number TABLE 2: Pathologic Findings for 21 Incidental Thyroid Nodules Noted on CT or MRI Category (Definition) All Nodules (n = 21) Nodules Requiring Fine-Needle Aspiration (n = 21) I (nondiagnostic or unsatisfactory) 0 0 Nodules Requiring Surgery (n = 2) II (benign) 16 (76) 16 (76) III (AUS/FLUS) 2 (10) 2 (10) 1 (50) IV (follicular neoplasm or 1 (5) 1 (5) suspicious for follicular neoplasm) V (suspicious for malignancy) 0 0 VI (malignant) 2 (10) 2 (10) 1 (50) Note Data are no. (%) of incidental thyroid nodules. AUS/FLUS = atypia of undetermined significance or follicular lesion of undetermined significance. TABLE 3: American College of Radiology () White Paper Recommendations Applied to Patients With Incidental Thyroid Nodules (ITNs) for Which Results of Cytopathologic Analysis Were Available White Paper Status, Category Bethesda Category II Bethesda Categories I and III Bethesda Categories IV VI positive Category Category Category negative a Total Note Cytopathologic categories are based on the Bethesda system of reporting thyroid cytopathologic findings, which recommends that no further procedures be performed for category II (benign) nodules, whereas repeat biopsy should be performed for nodules in categories I and III, and diagnostic lobectomy or thyroidectomy should be done for nodules in categories IV VI [17]. positive = met white paper recommendations, negative = did not meet white paper recommendations. a The -negative malignancy was a 1.2-cm T1bN0MX papillary carcinoma. 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6 Tanpitukpongse et al. of reported nodules could be caused by two main factors. First, before the white paper recommendations, there were no established guidelines for the workup of ITNs seen on CT or MRI, which could result in radiologists having a low threshold for reporting thyroid findings, including small ITNs. Second, some patient factors that reduce the need for workup could have been unknown to the radiologist, such as other comorbid conditions or patients financial limitations. Ideally, the ITNs that are significant to radiologists should also be significant to clinicians. This study found that ITNs that were selected for workup by clinicians were found in younger patients and were larger. Nodule size cutoff values are used in existing sonographic guidelines as a criterion for additional evaluation. Ultrasound criteria from the Society of Radiologists in Ultrasound and the American Thyroid Association recommend size cutoff values of 1.5 cm and cm, respectively [7, 14]. Recently, a large population-based case-control study found a size of 2 cm to be a better predictor of malignancy [10]. Patient age is not a factor in any sonographic guidelines, but the tendency of our clinicians to work up younger patients may be justified. The ratio of malignant to benign nodules is higher in younger patients [3, 18 22], and a recent study showed a slightly higher risk of tumor progression in young patients (defined as patients younger than 40 years) than in older patients with subclinical low-risk papillary thyroid cancers who undergo observation rather than surgery [24]. It is important to note that the two factors associated with subsequent workup patient age and nodule size are included as formal criteria in the white paper recommendations and the three-tiered system for ITNs seen on CT, MRI, and PET. These two categorization methods aim to reduce workup of benign nodules while detecting cancer at a clinically significant stage. In two other studies that applied the three-tiered system, no malignancies were missed, and there was a 35% reduction in the workup rate compared with existing biopsy practices, and a 46% reduction, in workup rate compared with the use of a size cutoff of 1 cm [2, 13]. Our study showed that the white paper recommendations could halve the number of nodules reported in the impression section of radiology reports, which could have also halved the number of patients undergoing FNA. However, one localized 12-mm papillary thyroid cancer would have been missed. Although it may be daunting to miss any malignancy, it is important to appreciate that small papillary thyroid cancers are generally indolent. According to the 2009 Surveillance Epidemiology and End Results (SEER) program database, the 10-year survival rate for a patient with a 10- to 14-mm localized tumor is more than 99.6% [25]. Several experts believe that many of these patients will die with, rather than of, thyroid cancer [8, 9]. It is also important to acknowledge that the false-negative rate associated with the white paper recommendations or threetiered system should not be made on the basis of a limited number of two malignancies. Prior studies have evaluated the use of the three-tiered system with a larger number of patients with cytologic findings [2, 13, 16]. There are several limitations to this study. First, this is a retrospective study performed at a single institution, which may differ from other institutions with regard to the reporting and workup of thyroid nodules detected on CT or MRI. Second, the text search of radiology reports underestimates the number of incidental thyroid findings by searching only for the phrase thyroid nodule and not including other related terms, such as mass, hypodensity, or lesion. However, using this single search term provided a sufficient sample size of more than 400 patients in this 12-month study to determine the workup rate of reported nodules. Although we may have underestimated the absolute number of thyroid nodules that received workup, the proportion of reported nodules that received workup would likely be similar. Third, the white paper recommendations were not applied to patients who did not have nodule size reported in the radiology reports. However, excluding these patients may not markedly affect our estimate of the reduction in the number of ITNs associated with use of the white paper recommendations because nodules without size measurement are more likely to be smaller and are less likely to be reported in the impression section. Finally, it is possible that some patients may have been lost to follow-up and may have received further workup at a different institution. We attempted to estimate the workup rate by collecting data on subsequent outpatient encounters after CT or MRI, and we found that 91% of the patients had additional records at our institution. This study shows that radiologists reports of ITNs on CT or MRI appear to be redundant and not concordant with the ITNs for which clinicians perform workup. Although it is well known that clinicians make their own decision as to which ITNs require workup, the results of this study provide a new perspective on the actual workup rate. Overall, the radiologist s approach to reporting ITNs observed on CT or MRI should differ from the approach used in ultrasound examination of the thyroid. Radiologists should appreciate that the thyroid gland is the focus of thyroid ultrasound and that an ITN noted on ultrasound is still a finding in the organ of interest. However, ITNs seen on CT or MRI are almost always unrelated to the primary problem for imaging, and highlighting an ITN in the impression section may draw attention and prompt unnecessary workup [10]. Conclusion There is discordance between the reporting and workup of ITNs, with only one in five ITNs reported in the impression section of radiology reports undergoing additional evaluation. The factors that influence clinicians decision to perform additional workup of ITNs are younger patient age and larger nodule size. These criteria are part of the white paper recommendations for the workup of ITNs identified on CT or MRI. Such guidelines have the potential to reduce the number of ITNs reported in the impression section of cross-sectional imaging reports and improve standardization of radiology reports. References 1. Yousem DM, Huang T, Loevner LA, Langlotz CP. Clinical and economic impact of incidental thyroid lesions found with CT and MR. AJNR 1997; 18: Nguyen XV, Choudhury KR, Eastwood JD, et al. Incidental thyroid nodules on CT: evaluation of 2 risk-categorization methods for work-up of nodules. AJNR 2013; 34: Shetty SK, Maher MM, Hahn PF, Halpern EF, Aquino SL. Significance of incidental thyroid lesions detected on CT: correlation among CT, sonography, and pathology. AJR 2006; 187: Hoang JK, Raduazo P, Yousem DM, Eastwood JD. What to do with incidental thyroid nodules on imaging? An approach for the radiologist. Semin Ultrasound CT MR 2012; 33: Hoang JK, Riofrio A, Bashir MR, Kranz PG, Eastwood JD. High variability in radiologists reporting practices for incidental thyroid nodules detected on CT and MRI. AJNR 2014; 35: Grady AT, Sosa JA, Tanpitukpongse TP, Choudhury KR, Gupta RT, Hoang JK. Radiology reports 1286 AJR:205, December 2015

7 Reporting and Workup of Incidental Thyroid Nodules Noted on CT or MRI for incidental thyroid nodules on CT and MRI: 13. Hobbs HA, Bahl M, Nelson RC, et al. Incidental nodules in children: current profile of a changing high variability across subspecialties. AJNR thyroid nodules detected at imaging: can diagnos- disease. South Med J 1989; 82: ; 36: tic workup be reduced by use of the Society of 20. Kirkland RT, Kirkland JL, Rosenberg HS, Har- 7. Cooper DS, Doherty GM, Haugen BR et Radiologists in Ultrasound recommendations and berg FJ, Librik L, Clayton GW. Solitary thyroid al. American Thyroid Association (ATA) Guide- the three-tiered system? AJR 2014; 202:18 24 nodules in 30 children and report of a child with a lines Taskforce on Thyroid Nodules and Differen- 14. Frates MC, Benson CB, Charboneau JW, et al. thyroid abscess. Pediatrics 1973; 51:85 90 tiated Thyroid Cancer; Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid 2009; 19: Davies L, Welch HG. Current thyroid cancer trends in the United States. JAMA Otolaryngol Head Neck Surg 2014; 140: Ito Y, Miyauchi A, Inoue H, et al. An observational trial for papillary thyroid microcarcinoma in Japanese patients. World J Surg 2010; 34: Smith-Bindman R, Lebda P, Feldstein VA, et al. Risk of thyroid cancer based on thyroid ultrasound imaging characteristics: results of a population-based study. JAMA Intern Med 2013; 173: Bahl M, Sosa JA, Nelson RC, Hoang JK. Imaging-detected incidental thyroid nodules that undergo surgery: a single-center experience over 1 year. AJNR 2014; 35: Hoang JK, Grady AT, Nguyen XV. What to do with incidental thyroid nodules identified on imaging studies? Review of current evidence and recommendations. Curr Opin Oncol 2015; 27:8 14 Management of thyroid nodules detected at US: Society of Radiologists in Ultrasound consensus conference statement. Radiology 2005; 237: Hoang JK, Langer JE, Middleton WD, et al. Managing incidental thyroid nodules detected on imaging: white paper of the Incidental Thyroid Findings Committee. J Am Coll Radiol 2015; 12: Bahl M, Sosa JA, Eastwood JD, Hobbs HA, Nelson RC, Hoang JK. Using the 3-tiered system for categorizing workup of incidental thyroid nodules detected on CT, MRI, or PET/CT: how many cancers would be missed? Thyroid 2014; 24: Cibas ES, Ali SZ. The Bethesda System for reporting thyroid cytopathology. Am J Clin Pathol 2009; 132: Belfiore A, La Rosa GL, La Porta GA, et al. Cancer risk in patients with cold thyroid nodules: relevance of iodine intake, sex, age, and multinodularity. Am J Med 1992; 93: Fowler CL, Pokorny WJ, Harberg FJ. Thyroid 21. Machens A, Holzhausen HJ, Dralle H. The prognostic value of primary tumor size in papillary and follicular thyroid carcinoma. Cancer 2005; 103: Rago T, Fiore E, Scutari M, et al. Male sex, single nodularity, and young age are associated with the risk of finding a papillary thyroid cancer on fine-needle aspiration cytology in a large series of patients with nodular thyroid disease. Eur J Endocrinol 2010; 162: Tan GH, Gharib H. Thyroid incidentalomas: management approaches to nonpalpable nodules discovered incidentally on thyroid imaging. Ann Intern Med 1997; 126: Ito Y, Miyauchi A, Kihara M, Higashiyama T, Kobayashi K, Miya A. Patient age is significantly related to the progression of papillary microcarcinoma of the thyroid under observation. Thyroid 2014; 24: National Cancer Institute. Surveillance epidemiology and end results data 1983 to National Cancer Institute website. seer.cancer.gov/data. Accessed December 2012 AJR:205, December