Application of Artificial Intelligence Computer-Assisted Diagnosis Originally Developed for Thyroid Nodules to Breast Lesions on Ultrasound.

As thyroid and breast cancer have several US findings in common, we applied an artificial intelligence computer-assisted diagnosis (AI-CAD) software originally developed for thyroid nodules to breast lesions on ultrasound (US) and evaluated its diagnostic performance. From January 2017 to December 2017, 1042 breast lesions (mean size 20.2 ± 11.8 mm) of 1001 patients (mean age 45.9 ± 12.9 years) who underwent US-guided core-needle biopsy were included. An AI-CAD software that was previously trained and validated with thyroid nodules using the convolutional neural network was applied to breast nodules. There were 665 benign breast lesions (63.0%) and 391 breast cancers (37.0%). The area under the receiver operating characteristic curve (AUROC) of AI-CAD to differentiate breast lesions was 0.678 (95% confidence interval: 0.649, 0.707). After fine-tuning AI-CAD with 1084 separate breast lesions, the diagnostic performance of AI-CAD markedly improved (AUC 0.841). This was significantly higher than that of radiologists when the cutoff category was BI-RADS 4a (AUC 0.621, P < 0.001), but lower when the cutoff category was BI-RADS 4b (AUC 0.908, P < 0.001). When applied to breast lesions, the diagnostic performance of an AI-CAD software that had been developed for differentiating malignant and benign thyroid nodules was not bad. However, an organ-specific approach guarantees better diagnostic performance despite the similar US features of thyroid and breast malignancies.

Implications of US radiomics signature for predicting malignancy in thyroid nodules with indeterminate cytology.

OBJECTIVES: The purpose of this study was to evaluate the role of the radiomics score using US images to predict malignancy in AUS/FLUS and FN/SFN nodules. METHODS: One hundred fifty-five indeterminate thyroid nodules in 154 patients who received initial US-guided FNA for diagnostic purposes were included in this retrospective study. A representative US image of each tumor was acquired, and square ROIs covering the whole nodule were drawn using the Paint program of Windows 7. Texture features were extracted by in-house texture analysis algorithms implemented in MATLAB 2019b. The LASSO logistic regression model was used to choose the most useful predictive features, and ten-fold cross-validation was performed. Two prediction models were constructed using multivariable logistic regression analysis: one based on clinical variables, and the other based on clinical variables with the radiomics score. Predictability of the two models was assessed with the AUC of the ROC curves. RESULTS: Clinical characteristics did not significantly differ between malignant and benign nodules, except for mean nodule size. Among 730 candidate texture features generated from a single US image, 15 features were selected. Radiomics signatures were constructed with a radiomics score, using selected features. In multivariable logistic regression analysis, higher radiomics score was associated with malignancy (OR = 10.923; p < 0.001). The AUC of the malignancy prediction model composed of clinical variables with the radiomics score was significantly higher than the model composed of clinical variables alone (0.839 vs 0.583). CONCLUSIONS: Quantitative US radiomics features can help predict malignancy in thyroid nodules with indeterminate cytology.

Comparison of diagnostic performance of the ACR and Kwak TIRADS applying the ACR TIRADS' size thresholds for FNA.

OBJECTIVE: To investigate the diagnostic performances and unnecessary fine-needle aspiration (FNA) rates of two point-scale based TIRADS and compare them with a modified version using the ACR TIRADS' size thresholds. METHODS: Our Institutional Review Board approved this retrospective study and waived the requirement for informed consent. A total of 2106 thyroid nodules 10 mm or larger in size in 2084 patients with definitive cytopathologic findings were included. Ultrasonography categories were assigned according to each guideline. We applied the ACR TIRADS' size thresholds for FNA to the Kwak TIRADS and defined it as the modified Kwak TIRADS (mKwak TIRADS). Diagnostic performances and unnecessary FNA rates were evaluated for both the original and modified guidelines. RESULTS: Of the original guidelines, the ACR TIRADS had higher specificity, accuracy, and area under the receiver operating characteristic curve (AUC) (63.1%, 68.9%, and 0.748, respectively). When the size threshold of the ACR TIRADS was applied to the Kwak TIRADS, the resultant mKwak TIRADS had higher specificity, accuracy, and AUC (64.7%, 70.3%, and 0.765, respectively) than the ACR TIRADS. The mKwak TIRADS also had a lower unnecessary FNA rate than the ACR TIRADS (54.8% and 56.4%, respectively). The false-negative rate of the Kwak TIRADS was the lowest (1.9%) among all TIRADS. CONCLUSION: The modified Kwak TIRADS incorporating the size thresholds of the ACR TIRADS showed higher diagnostic performance and a lower unnecessary FNA rate than the original point-scale based TIRADS. KEY POINTS: • Of the original guidelines, the ACR TIRADS had the highest specificity, accuracy, and area under the receiver operating characteristic curve (AUC) (63.1%, 68.9%, and 0.748, respectively). • When the size threshold of the ACR TIRADS was applied to the Kwak TIRADS, the resultant modified version of Kwak TIRADS had higher specificity, accuracy, and AUC (64.7%, 70.3%, and 0.765, respectively) than the ACR TIRADS. • The false-negative rate of the Kwak TIRADS was the lowest (1.9%) among all TIRADS.

Combining radiomics with ultrasound-based risk stratification systems for thyroid nodules: an approach for improving performance.

OBJECTIVES: To develop a radiomics score using ultrasound images to predict thyroid malignancy and to investigate its potential as a complementary tool to improve the performance of risk stratification systems. METHODS: We retrospectively included consecutive patients who underwent fine-needle aspiration (FNA) for thyroid nodules that were cytopathologically diagnosed as benign or malignant. Nodules were randomly assigned to a training and test set (8:2 ratio). A radiomics score was developed from the training set, and cutoff values based on the maximum Youden index (Rad_maxY) and for 5%, 10%, and 20% predicted malignancy risk (Rad_5%, Rad_10%, Rad_20%, respectively) were applied to the test set. The performances of the American College of Radiology (ACR) and the American Thyroid Association (ATA) guidelines were compared with the combined performances of the guidelines and radiomics score with interpretations from expert and nonexpert readers. RESULTS: A total of 1624 thyroid nodules from 1609 patients (mean age, 50.1 years [range, 18-90 years]) were included. The radiomics score yielded an AUC of 0.85 (95% CI: 0.83, 0.87) in the training set and 0.75 (95% CI: 0.69, 0.81) in the test set (Rad_maxY). When the radiomics score was combined with the ACR or ATA guidelines (Rad_5%), all readers showed increased specificity, accuracy, and PPV and decreased unnecessary FNA rates (all p < .05), with no difference in sensitivity (p > .05). CONCLUSION: Radiomics help predict thyroid malignancy and improve specificity, accuracy, PPV, and unnecessary FNA rate while maintaining the sensitivity of the ACR and ATA guidelines for both expert and nonexpert readers. KEY POINTS: • The radiomics score yielded an AUC of 0.85 and 0.75 in the training and test set, respectively. • For all readers, combining a 5% predicted malignancy risk cutoff for the radiomics score with the ACR and ATA guidelines significantly increased specificity, accuracy, and PPV and decreased unnecessary FNA rates, with no decrease in sensitivity. • Radiomics can help predict malignancy in thyroid nodules in combination with risk stratification systems, by improving specificity, accuracy, and PPV and unnecessary FNA rates while maintaining sensitivity for both expert and nonexpert readers.

Pattern-based vs. score-based guidelines using ultrasound features have different strengths in risk stratification of thyroid nodules.

OBJECTIVE: To evaluate and compare the diagnostic performances between recently published pattern-based and score-based TIRADS according to the experience level of the performer. METHODS: From July 2013 to January 2019, 8657 thyroid nodules in 8364 patients that had been cytopathologically diagnosed as benign or malignant were included (mean size, 22.0 mm ± 12.1). Thyroid nodules were categorized into US-based final assessment categories and US-FNA indications of five recently published TIRADS. Radiologists performing the US examinations were divided into the experienced vs. inexperienced group. Diagnostic performances and unnecessary biopsy rates were calculated and compared between the five TIRADS, also the experienced vs. inexperienced group. RESULTS: Of the 8657 thyroid nodules, 6706 (77.5%) were benign and 1951 (22.5%) were malignant. Diagnostic performances for US-based final assessment categories showed higher sensitivity and NPV for EU-TIRADS (92.7% and 96.5%), while Kwak-TIRADS had higher specificity, PPV, accuracy, and AUC (89.6%, 68.0%, 86.5%, and 0.878; all p < 0.05, respectively). Diagnostic performances for US-FNA indications showed higher sensitivity and NPV for KTA/KSThR TIRADS (98.5% and 97.0%), while Kwak-TIRADS had higher specificity, PPV, accuracy, and AUC (70.3%, 46.6%, 74.5%, and 0.797; all p < 0.05, respectively). Unnecessary biopsy rates were the lowest in Kwak-TIRADS for both US categories and US-FNA indications (32.0% and 53.4%, p < 0.001). Similar trends were seen in both the experienced and inexperienced group. CONCLUSION: The currently published score-based guidelines for thyroid nodules have significantly higher specificity, PPV, accuracy, and AUC and lower unnecessary biopsy rates, whereas pattern-based guidelines have higher sensitivity and NPV, regardless of the level of experience of the performer. KEY POINTS: • For US-based final assessment categories, EU-TIRADS had higher sensitivity and NPV, while Kwak-TIRADS had higher specificity, PPV, accuracy, and AUC. • For US-FNA indications, KTA/KSThR TIRADS had higher sensitivity and NPV, while Kwak-TIRADS had higher specificity, PPV, accuracy, and AUC. • Similar trends were seen in diagnostic performances for both experienced and inexperienced groups.

Guideline Implementation on Fine-Needle Aspiration for Thyroid Nodules: Focusing on Micronodules.

OBJECTIVE: We investigated patients who were referred to our institution after fine-needle aspiration (FNA) was performed at outside clinics to evaluate how many nodules satisfied the FNA indications of the Korean Thyroid Imaging Reporting and Data System (K-TIRADS) and compare that to the number of thyroid nodules that satisfy the FNA indications of the American College of Radiology (ACR)-TIRADS and American Thyroid Association (ATA) guidelines. METHODS: Between January 2018 and December 2018, 2,628 patients were included in our study. The included patients were those referred for thyroid surgery after having a suspicious thyroid nodule. We retrospectively applied the three guidelines to each thyroid nodule and determined whether each nodule satisfied the FNA indications. We compared the proportion of nodules satisfying the FNA indications of each guideline using a generalized linear model and generalized estimating equation. RESULTS: The median size of the 2,628 thyroid nodules was 0.9 cm (range, 0.2 to 9.5 cm). We found that FNA was not indicated for 54.1%, 47.7%, and 19.1% of nodules and 87.3%, 99.0%, and 97.8% among them were micronodules (<1 cm) according to the ACR-TIRADS, ATA guideline, and K-TIRADS, respectively. The proportion of micronodules which satisfied the FNA indications was significantly higher for the K-TIRADS (65.1%) compared to the ACR TIRADS (12.1%) and ATA guideline (12.1%) (P<.001). CONCLUSION: Among patients referred for thyroid surgery to our institutions, about 35% of the micronodules underwent FNA despite not being appropriate for indications by the K-TIRADS. Systematic training for physicians as well as modifications to increase the sensitivity of the guideline may be needed to reduce the overdiagnosis of thyroid cancers, especially for micronodules.

Grayscale Ultrasound Radiomic Features and Shear-Wave Elastography Radiomic Features in Benign and Malignant Breast Masses.

PURPOSE: To identify and compare diagnostic performance of radiomic features between grayscale ultrasound (US) and shear-wave elastography (SWE) in breast masses. MATERIALS AND METHODS: We retrospectively collected 328 pathologically confirmed breast masses in 296 women who underwent grayscale US and SWE before biopsy or surgery. A representative SWE image of the mass displayed with a grayscale image in split-screen mode was selected. An ROI was delineated around the mass boundary on the grayscale image and copied and pasted to the SWE image by a dedicated breast radiologist for lesion segmentation. A total of 730 candidate radiomic features including first-order statistics and textural and wavelet features were extracted from each image. LASSO regression was used for data dimension reduction and feature selection. Univariate and multivariate logistic regression was performed to identify independent radiomic features, differentiating between benign and malignant masses with calculation of the AUC. RESULTS: Of 328 breast masses, 205 (62.5 %) were benign and 123 (37.5 %) were malignant. Following radiomic feature selection, 22 features from grayscale and 6 features from SWE remained. On univariate analysis, all 6 SWE radiomic features (P < 0.0001) and 21 of 22 grayscale radiomic features (P < 0.03) were significantly different between benign and malignant masses. After multivariate analysis, three grayscale radiomic features and two SWE radiomic features were independently associated with malignant breast masses. The AUC was 0.929 for grayscale US and 0.992 for SWE (P < 0.001). CONCLUSION: US radiomic features may have the potential to improve diagnostic performance for breast masses, but further investigation of independent and larger datasets is needed.

Validation of the 2015 American Thyroid Association Management Guidelines for Thyroid Nodules With Benign Cytologic Findings in the Era of the Bethesda System.

OBJECTIVE: The purpose of this study is to investigate follow-up strategies for cytologically benign thyroid nodules according to size and ultrasound (US) pattern according to the 2015 American Thyroid Association (ATA) guidelines in the era of the Bethesda system. MATERIALS AND METHODS: This retrospective study included 1208 patients with 1230 nodules that were cytologically benign at initial fine-needle aspiration performed from June 2012 to December 2014. False-negative rates (FNRs) were calculated by considering nodule size and US pattern according to the 2015 ATA guidelines and were compared between nodules with the high-suspicion US pattern and nodules with the high- or intermediate-suspicion US patterns according to size. RESULTS: Twenty-five of the 1230 nodules (2.0%) were malignant. The FNRs were 5.1% (8/158) for nodules with the high-suspicion US pattern and 1.6% (17/1072) for nodules with other US patterns. With regard to nodule size, the FNRs were 3.2% (9/277) for nodules 3 cm or larger and 5.2% (6/115) for nodules 4 cm or larger. The FNRs of nodules with the high-suspicion pattern were not significantly higher than those of nodules with the high- or intermediate-suspicion patterns among nodules 2 cm or larger (2.5% vs 1.9%; p = 0.208), 3 cm or larger (3.4% vs 2.9%; p = 0.498), and 4 cm or larger (5.4% vs 3.8%; p = 0.353). CONCLUSION: Thyroid nodules with initial benign cytologic findings had a low malignancy rate in the era of the Bethesda system, regardless of US pattern and size. Therefore, any immediate diagnostic intervention may be discouraged in cytologically benign nodules.

Thyroid Nodules With Nondiagnostic Cytologic Results: Follow-Up Management Using Ultrasound Patterns Based on the 2015 American Thyroid Association Guidelines.

OBJECTIVE: The purpose of this study was to evaluate the malignancy rate of nodules with nondiagnostic cytologic results based on the American Thyroid Association (ATA) ultrasound (US) patterns and to suggest management guidelines for these nodules. MATERIALS AND METHODS: From January 2013 to December 2014, 441 nodules (≥ 1 cm) were found in 437 patients with nondiagnostic results of ultrasound (US)-guided fine-needle aspiration biopsy (nondiagnostic nodules). A total of 191 nodules that were cytopathologically confirmed or were smaller (> 3 mm) at follow-up US were enrolled. The US findings of each nodule were reviewed. One radiologist classified the nodules into the following five categories according to the 2015 ATA guidelines: high, intermediate, low, and very low suspicion for malignancy and benign. The reference standard was histopathologic confirmation. Nodules that were smaller at follow-up US were considered benign. The malignancy rate of each category was calculated. RESULTS: Among a total 191 nodules, 20 (10.5%) were malignant. Solid composition, marked hypoechogenicity, microlobulated or irregular margins, microcalcifications, and taller-than-wide shape were more frequently seen in malignant nodules (all p < 0.001). The malignancy rate of nodules with very low suspicion of malignancy was 0% (0/58); low, 0% (0/45); intermediate, 10.3% (6/58); and high, 46.7% (14/30) (p < 0.001). CONCLUSION: When US findings of thyroid nodules are assessed according to the 2015 ATA guidelines, nondiagnostic thyroid nodules with very-low- or low-suspicion US patterns can be followed up with US. Nondiagnostic nodules with intermediate or highly suspicious US patterns should be evaluated with repeat US-guided fine-needle aspiration biopsy.

Non-diagnostic thyroid nodules after application of the Bethesda system: a study evaluating the interval for repeat aspiration for non-diagnostic results.

Background The non-diagnostic category of the Bethesda system has a low malignancy rate; nevertheless, repeat ultrasonography-guided fine needle aspiration (US-FNA) is recommended with no consensus for follow-up intervals. Purpose To investigate whether a six-month time interval for repeat US-FNA is appropriate for non-diagnostic thyroid nodules after applying the Bethesda system. Material and Methods From January 2010 to January 2014, 322 thyroid nodules ≥10 mm with non-diagnostic results on initial US-FNA with any follow-up with US or US-FNA were included (mean age = 52.2 years ± 12.4). Clinical and US features were compared according to size change (increase, no change, decrease) and follow-up interval (<6 months and ≥6 months after initial US-FNA), and the minimal time interval observed in nodules with size increase on follow-up. The outcome of non-diagnostic nodules according to follow-up interval and size change were evaluated. Results Of the 322 nodules, 13 (4.0%) were malignant and 309 (96.0%) were benign. None of the 82 nodules with decreased size were malignant and 90.2% nodules with decreased size were found after six months. Of 175 nodules with repeat US-FNA, repeat cytology results did not differ significantly between the groups with follow-up US-FNA before and after six months ( P = 0.337). No significant differences were seen in size or extrathyroidal extension among the 13 malignant nodules according to the six-month interval (all P > 0.05), and no lateral lymph node metastasis was present. Conclusion Repeat US-FNA for initially non-diagnostic thyroid nodules can be performed at a six-month interval after initial procedure without tumor progression.

Diagnostic performances and interobserver agreement according to observer experience: a comparison study using three guidelines for management of thyroid nodules.

Background The differences regarding categorization of thyroid nodules among different guidelines may affect the diagnostic performances and agreement among observers. Purpose To compare the diagnostic performances and agreements between observers with various degree of experience when applying different guidelines for stratifying thyroid nodules using suspicious ultrasonography (US) features. Material and Methods This retrospective study included 370 thyroid nodules (≥10 mm). Four observers, grouped as experienced and inexperienced, evaluated the US features and made final assessments according to the Kim criteria, Thyroid Imaging Reporting and Data System (TIRADS) by Kwak et al., and the 2015 American Thyroid Association (ATA) guideline. Diagnostic performances and agreements among the two groups were compared. Results The Kim criteria shows higher specificity with significantly lower sensitivity when compared to TIRADS and the 2015 ATA guideline (all P < 0.001), regardless of the level of experience. The experienced group showed significantly higher specificity with the Kim criteria and the 2015 ATA guideline compared to the inexperienced group ( P < 0.001), and the inexperienced group showed significantly higher sensitivity using the Kim criteria ( P = 0.002). The experienced group showed significantly higher agreement than the inexperienced group when using TIRADS while higher agreement was seen when using the 2015 ATA guideline for the inexperienced group. Agreement was not significantly different for the Kim criteria according to observer experience. Conclusion The diagnostic performances and agreements show significant differences in risk stratification of thyroid nodules according to the three guidelines using suspicious US features and the level of experience of the observer.

Qualitative and Semiquantitative Elastography for the Diagnosis of Intermediate Suspicious Thyroid Nodules Based on the 2015 American Thyroid Association Guidelines.

OBJECTIVES: To evaluate qualitative and semiquantitative elastography for the diagnosis of intermediate suspicious thyroid nodules based on the 2015 American Thyroid Association (ATA) guidelines. METHODS: Through a retrospective search of our institutional database, 746 solid thyroid nodules found on grayscale ultrasonography, strain elastography, and ultrasound-guided fine-needle aspiration between June and November 2009 were collected. Among them, 80 nodules from 80 patients with an intermediate suspicion of malignancy based on the 2015 ATA guidelines that were 10 mm or larger were recruited as the final study nodules. Elastographic findings were categorized according to the criteria of Rago et al (J Clin Endocrinol Metab 2007; 92:2917-2922) and Asteria et al (Thyroid 2008; 18:523-531), and strain ratio values were calculated and recorded. The independent 2-sample t test and χ2 test (or Fisher exact test) were used to evaluate differences in clinical parameters between benign and malignant thyroid nodules. All variables were compared by univariate and multivariate logistic regression analyses, and odds ratios with 95% confidence intervals were calculated. RESULTS: Of the 80 nodules, 6 (7.5%) were malignant, and 74 (92.5%) were benign. No significant differences were observed in age, sex, nodule size, elasticity score, and strain ratio between benign and malignant nodules. No variables significantly predicted thyroid malignancy on the univariate analysis. On the multivariate logistic regression analysis, there were no independent variables associated with thyroid malignancy, including the elasticity score and strain ratio (all P > .05). CONCLUSIONS: Elastographic analysis using the elasticity score and strain ratio has limited ability to characterize the benignity or malignancy of thyroid nodules with an intermediate suspicion of malignancy based on the 2015 ATA guidelines.

Diagnosis and Management of Small Thyroid Nodules: A Comparative Study with Six Guidelines for Thyroid Nodules.

Purpose To investigate the diagnostic performances of six guidelines used to assess thyroid nodules and to determine whether any of these guidelines identify cancers of aggressive form in this population. Materials and Methods From March 2007 to February 2010, 4696 thyroid nodules that were 1-2 cm in 4585 patients were diagnosed as benign or malignant on the basis of cytopathologic results. Ultrasonographic examinations of the thyroid nodules were retrospectively reviewed and categorized according to the categories defined by six previously published guidelines for thyroid nodules. Diagnostic performances of each guideline for diagnosing thyroid cancer were calculated and compared by using the generalized estimating equation method for logistic regression. Multivariate regression analysis was used to analyze predictors for distant metastasis and recurrence and persistence in patients with small thyroid cancer. Results Of the 4696 thyroid nodules, 3652 (77.8%) were benign and 1044 (22.2%) were malignant. Followed were 873 patients who were diagnosed with small thyroid cancer, of whom 12 had distant metastasis and 66 had recurrence or persistence of disease. Specificity, positive predictive value, and accuracy were highest with criteria developed by Kim et al (83.1%, 59.6%, and 84.0%, respectively), while sensitivity and negative predictive value were highest with Thyroid Imaging Reporting and Data System developed by Kwak et al (98.8% and 98.6%, respectively; P < .001). Positive findings that indicated fine-needle aspiration in the guidelines did not show significant association with distant metastasis or recurrence or persistence (P > .05), but the study power was low to detect a difference. Conclusion With its high specificity and accuracy, criteria from Kim et al may be an effective guideline to use in the management of small thyroid nodules. © RSNA, 2016 Online supplemental material is available for this article.

Fine-needle aspiration versus core needle biopsy for diagnosis of thyroid malignancy and neoplasm: a matched cohort study.

OBJECTIVES: To compare the diagnostic performances of fine-needle aspiration (FNA) and core needle biopsy (CNB) in the diagnosis of thyroid malignancy and neoplasm in patients who underwent surgery for thyroid nodules. METHODS: This retrospective study was approved by the institutional review board, and the need to obtain informed consent was waived. 3192 patients who underwent FNA (n = 3048) or CNB (n = 144) for diagnosis of thyroid nodules and then proceeded with surgery were included. Surgical pathologic diagnosis was the reference standard. Diagnostic performances of FNA and CNB to predict malignancy and neoplasm were compared. Propensity score matching was used to match patients with FNA with those with CNB because there were significant differences in the number of nodules and nodule characteristics between the FNA and CNB groups. RESULTS: Before matching, the sensitivity and accuracy of FNA were significantly higher or comparable with those of CNB, and the specificity, negative predictive value and positive predictive value were comparable. After matching, the diagnostic performances were similar, with the exception of specificity for predicting neoplasm being higher with CNB than with FNA. CONCLUSION: FNA showed comparable diagnostic performance to CNB; therefore, there may be no benefit in performing CNB to diagnose papillary thyroid carcinoma and neoplasm. KEY POINTS: • Diagnostic performances of FNA and CNB for thyroid malignancy and neoplasm were compared. • FNA showed comparable performances to CNB both before and after statistical matching. • There may be no benefit in performing CNB, given the comparable performances.

Malignancy Risk Stratification of Thyroid Nodules: Comparison between the Thyroid Imaging Reporting and Data System and the 2014 American Thyroid Association Management Guidelines.

PURPOSE: To compare malignancy risk stratification of thyroid nodules with the 2014 American Thyroid Association (ATA) management guidelines and the Thyroid Imaging Reporting and Data System (TIRADS). MATERIALS AND METHODS: This retrospective study was approved by the institutional review board. The requirement to obtain informed consent was waived. From November 2013 to July 2014, 1293 thyroid nodules in 1241 patients (mean age, 50.8 years ± 13.5) were included in this study. All nodules measured at least 10 mm. Solidity, hypoechogenicity or marked hypoechogenicity, microlobulated to irregular margin, microcalcifications or mixed calcifications, and nonparallel shape were considered suspicious features at ultrasonography (US). A TIRADS category and the US pattern as determined with ATA guidelines were assigned to each nodule. The correlation between the TIRADS category or ATA pattern and the malignancy rate was evaluated with the Spearman rank test. RESULTS: Of the 1293 thyroid nodules, 1059 (81.9%) were benign and 234 (18.1%) were malignant. Forty-four of the 1293 nodules (3.4%) did not meet the criteria for the ATA patterns and were classified as "not specified." The malignancy rates of TIRADS category 3, 4a, 4b, 4c, and 5 nodules were 1.9% (six of 316 nodules), 4.2% (17 of 408 nodules), 12.9% (33 of 256 nodules), 49.8% (130 of 261 nodules), and 92.3% (48 of 52 nodules), respectively, with significant differences between categories (P < .001). Malignancy rates of nodules with very low, low, intermediate, and high suspicion for malignancy with the ATA guidelines and not specified patterns were 2.7% (11 of 407 nodules), 3.1% (10 of 323 nodules), 16.7% (39 of 233 nodules), 58.0% (166 of 286 nodules), and 18.2% (eight of 44 nodules), respectively, with significant differences between patterns (P < .001). There was high correlation between classification with TIRADS (r = 1.000, P < .001) and ATA guidelines (r = 0.900, P = 0.037), without statistically significant differences (P = .873). CONCLUSION: Both TIRADS and the ATA guidelines provide effective malignancy risk stratification for thyroid nodules. Nodules that do not meet the criteria for a specific pattern with the ATA guidelines have a relatively high risk of malignancy (18.2%).

Subcategorization of atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS): a study applying Thyroid Imaging Reporting and Data System (TIRADS).

OBJECTIVE: To evaluate the clinical significance and compare the imaging features according to the Thyroid Image Reporting and Data System (TIRADS) between atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) subcategories. DESIGN & PATIENTS: A total of 192 thyroid nodules in 188 patients (mean age: 50·2 ± 11·8 years) that had been initially diagnosed as AUS/FLUS on US-guided fine needle aspiration (US-FNA) were included. One cytopathologist retrospectively reviewed the cytology slides, subcategorizing cytology results into AUS and FLUS. A TIRADS category was assigned to each thyroid nodule according to the number of suspicious US features. Clinical, US features and malignancy rates were compared between the two subcategories. RESULTS: Of the 192 AUS/FLUS lesions, 149 (77·6%) were subcategorized as AUS and 43 (22·4%) as FLUS. Of the 192 AUS/FLUS nodules, 82 (42·7%) were malignant. The malignancy rates between AUS and FLUS subcategories were not significantly different, 45·6% to 32·6%, respectively (P = 0·127). When applying TIRADS, significant differences were seen in TIRADS category between benign and malignant nodules in the AUS subcategory (P < 0·001), but not in the FLUS subcategory (P = 0·414). The malignancy rates in TIRADS categories 3, 4a, 4b, 4c and 5 were 15·4%, 22·2%, 33·3%, 57·1% and 80·0% (P < 0·001) in AUS nodules and 40·0%, 50·0%, 23·5%, 22·2% and 0·0% (P = 0·414) in FLUS nodules, respectively. CONCLUSION: Suspicious US features are useful in predicting malignancy among AUS subcategories but not in FLUS subcategories. Subcategorization into AUS and FLUS cytology may be helpful in deciding upon treatment or management of thyroid nodules.

Repeat fine-needle aspiration can be performed at 6 months or more after initial atypia of undetermined significance or follicular lesion of undetermined significance results for thyroid nodules 10 mm or larger.

OBJECTIVES: To investigate whether repeat ultrasound-guided fine-needle aspiration (US-FNA) in initial atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS) results could be performed 6 months after or more. METHODS: A total of 221 AUS/FLUS ≥10 mm with any follow-up were grouped according to the first follow-up interval at less than 6 months (group 1, n = 87) and 6 months or more (group 2, n = 134). Clinical features, final assessment of ultrasound (US) or the Thyroid Imaging Reporting and Data System (TIRADS), tumour size, extrathyroidal extension and lymph node metastasis in malignancies were compared. RESULTS: Thirty-four (15.4 %) were malignant. Age, gender, size, final assessment, TIRADS and malignancy rate were not significantly different between the two groups (p = 0.660, 0.691, 0.502, 0.237, 0.819 and 0.420). Tumour size, extrathyroidal extension and lymph node metastasis were not significantly different between the two malignancy groups (p = 0.770, 0.611 and 0.068). Two of 10 nodules with increased size were malignancies found at 7.1 and 25.0 months. None of 33 nodules (14.9 %) with decreased size at a median 10 months were malignant. CONCLUSIONS: Repeat US-FNA performed on nodules ≥10 mm at 6 months or more after initial AUS/FLUS results can reduce unnecessary repeat US-FNAs without progression of malignancy. KEY POINTS: • Follow-up intervals of AUS/FLUS did not affect the malignancy rate • Tumour stage was not different according to the follow-up intervals • None of the nodules with decreased size were malignant • Repeat US-FNA can be performed at ≥6 months after initial AUS/FLUS.

Repeat Ultrasound-Guided Fine-Needle Aspiration for Thyroid Nodules 10 mm or Larger Can Be Performed 10.7 Months After Initial Nondiagnostic Results.

OBJECTIVE: The purpose of this study is to investigate when repeat ultrasound (US)-guided fine-needle aspiration (FNA) for thyroid nodules 10 mm or larger with initial nondiagnostic results due to inadequate or unsatisfactory specimen could be performed. MATERIALS AND METHODS: A total of 228 nodules 10 mm or larger with initial nondiagnostic results in 223 patients were classified into three groups according to the first follow-up US or US-guided FNA intervals after the initial US-guided FNA: within 3 months (group 1), 3-9 months (group 2), and more than 9 months (group 3). Nodules were classified according to size change. The malignancy detection rate and clinicopathologic characteristics were compared among the three groups. RESULTS: Seven nodules (3.1%) were malignant, and their cancer stages were the same as that determined at the initial US-guided FNA. Malignancy detection rates, as well as tumor size, extrathyroidal extension, and lymph node metastasis at pathologic analysis, were not significantly different among the three groups. Thirteen of 228 nodules (5.7%) showed increased size at a mean (± SD) of 34.5 ± 25.1 months (range, 10.7-84.7 months) after initial US-guided FNA, and one of the 13 nodules (7.7%) was malignant, a minimally invasive follicular carcinoma without lymph node metastasis found at 63.2 months. Of 177 nodules without change, six papillary thyroid carcinomas (3.4%) were found at a mean of 10.4 months. None of the 38 nodules with decreased size during a mean follow-up interval of 26.1 ± 19.8 months (range, 2.8-79.5 months) was malignant. CONCLUSION: Repeat US-guided FNA for initial nondiagnostic thyroid nodules after 10.7 months can reduce unnecessary repeat US-guided FNAs without progression of malignancy.

Quantitative Evaluation for Differentiating Malignant and Benign Thyroid Nodules Using Histogram Analysis of Grayscale Sonograms.

OBJECTIVES: To evaluate the diagnostic value of histogram analysis using grayscale sonograms for differentiation of malignant and benign thyroid nodules. METHODS: From July 2013 through October 2013, 579 nodules in 563 patients who had undergone ultrasound-guided fine-needle aspiration were included. For the grayscale histogram analysis, pixel echogenicity values in regions of interest were measured as 0 to 255 (0, black; 255, white) with in-house software. Five parameters (mean, skewness, kurtosis, standard deviation, and entropy) were obtained for each thyroid nodule. With principal component analysis, an index was derived. Diagnostic performance rates for the 5 histogram parameters and the principal component analysis index were calculated. RESULTS: A total of 563 patients were included in the study (mean age ± SD, 50.3 ± 12.3 years;range, 15-79 years). Of the 579 nodules, 431 were benign, and 148 were malignant. Among the 5 parameters and the principal component analysis index, the standard deviation (75.546 ± 14.153 versus 62.761 ± 16.01; P < .001), kurtosis (3.898 ± 2.652 versus 6.251 ± 9.102; P < .001), entropy (0.16 ± 0.135 versus 0.239 ± 0.185; P < .001), and principal component analysis index (-0.386±0.774 versus 0.134 ± 0.889; P < .001) were significantly different between the malignant and benign nodules. With the calculated cutoff values, the areas under the curve were 0.681 (95% confidence interval, 0.643-0.721) for standard deviation, 0.661 (0.620-0.703) for principal component analysis index, 0.651 (0.607-0.691) for kurtosis, 0.638 (0.596-0.681) for entropy, and 0.606 (0.563-0.647) for skewness. The subjective analysis of grayscale sonograms by radiologists alone showed an area under the curve of 0.861 (0.833-0.888). CONCLUSIONS: Grayscale histogram analysis was feasible for differentiating malignant and benign thyroid nodules but did not show better diagnostic performance than subjective analysis performed by radiologists. Further technical advances will be needed to objectify interpretations of thyroid grayscale sonograms.

Evaluation of Underlying Lymphocytic Thyroiditis With Histogram Analysis Using Grayscale Ultrasound Images.

OBJECTIVES: The purpose of this study was to evaluate diagnostic performance of histogram analysis using grayscale ultrasound (US) images in the diagnosis of lymphocytic thyroiditis. METHODS: Three radiologists reviewed a total of 505 US images and classified the images according to the presence/existence of lymphocytic thyroiditis. After 2 months, each reviewer repeated the process with the same 505 images in a randomly mixed order. The intraobserver and interobserver variability was analyzed with a generalized κ value. Four histogram parameters (mean value, standard deviation, skewness, and kurtosis) were obtained, and an index was calculated from principal component analysis. Diagnostic performances were compared. RESULTS: Of 505 patients, 125 (24.8%) had lymphocytic thyroiditis, and 380 (75.2%) had normal thyroid parenchyma on pathologic analysis. The κ value for intraobserver variance ranged from -0.002 to 0.781, and the overall κ values for interobserver variance were 0.570 and 0.214 in the first and second tests, respectively. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value for the 3 reviewers versus the principal component analysis index were 28.0% to 83.2%, 43.7% to 82.6%, 53.5% to 79.0%, 24.6% to 56.2%, and 75.2% to 88.9% versus 58.4%, 72.4%, 68.9%, 41.0%, and 84.1%. CONCLUSIONS: Histogram analysis of grayscale US images provided confirmable and quantitative information about lymphocytic thyroiditis and was comparable with performers' assessments in diagnostic performance.