Outcome of thyroid nodules characterized as atypia of undetermined significance or follicular lesion of undetermined significance and correlation with Ultrasound features and BRAF(V600E) mutation analysis

Evolving approaches in paediatric thyroid cytopathology: A review

The guidelines for the workup of thyroid nodules have been established in adult populations and secondarily applied to paediatric populations. In particular, The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) is commonly applied to both adult and paediatric thyroid nodules. However, as paediatric nodules have distinct molecular drivers and behavioural trajectories, there is renewed interest in diagnostic and management strategies that are paediatric specific. Here, we review key differences between paediatric and adult thyroid cancer and recent literature evaluating the use of TBSRTC in paediatric populations.

Clinico-cytopathological subcategorization in thyroid nodules of atypia of undetermined significance/follicular lesion of undetermined significance using the TIRADS and Bethesda classifications

Introduction

Bethesda category III - atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) is a heterogeneous class of the Bethesda system for thyroid nodules. In order to clarify the therapeutic road for clinicians, this category was subclassified based on the cytopathological features. In this study, we evaluated the risk of malignancy, surgical outcome, demographic characteristics, and correlation of ultrasound features with the final outcome in patients with thyroid nodules based on AUS/FLUS subclassification.

Method

After evaluating 867 thyroid nodules from three different centers, 70 (8.07%) were initially diagnosed as AUS/FLUS. The cytopathologists re-interpreted the FNA samples and subclassified them into five subcategories: architectural atypia, cytologic atypia, cytologic and architectural atypia, and Hürthle cell AUS/FLUS, and atypia, which was not specified. Based on the suspicious ultrasound features, an appropriate ACR TI-RADS score was allocated to each nodule. Finally, the malignancy rate, surgical outcomes, and ACR TI-RADS scores were evaluated among Bethesda category III nodules.

Results

Among the 70 evaluated nodules, 28 (40%) were subclassified as Hürthle cell AUS/FLUS, 22 (31.42%) as cytologic and architectural atypia, 8 (11.42%) as architectural atypia, 7 (10%) as cytologic atypia, and 5 (7.14%) as atypia which was not specified. The overall malignancy rate was 34.28%, and the architectural atypia and Hürthle cell nodules displayed lower malignancy compared to other groups (P-Value<0.05). Utilizing ACR TI-RADS scores showed no statistical significance between Bethesda III subcategorization and ACR TI-RADS scores. However, ACR TI-RADS can be a reliable predictor for Hürthle cell AUS/FLU nodules.

Conclusion

ACR TI-RADS helps evaluate malignancy only in the Hürthle cell AUS/FLUS subcategory of AUS/FLUS. Besides, cytopathological reporting based on the suggested AUS/FLUS subclassification could help clinicians take appropriate measures to manage thyroid nodules.

Optimization of the Management of Category III Thyroid Nodules Using Repeat FNA and TIRADS

The aim of the study was to examine the benefits of the joint use of repeat FNA (rFNA) and EU-TIRADS in category III nodules in relation to the kind of atypia: nuclear vs. architectural (denoted by AUS and FLUS respectively). The study included 127 AUS and 1739 FLUS nodules with a known category of EU-TIRADS. Repeat FNA was performed in 82 AUS and 934 FLUS nodules of which 57 and 515 were excised, respectively. AUS nodules had higher malignancy risk than FLUS nodules. EU-TIRADS showed higher accuracy for AUS nodules, the opposite to rFNA, that had higher accuracy for FLUS nodules. The combined criterion for AUS nodules (at least rFNA-V or EU-TIRADS-4) maximized sensitivity (92.3%) with acceptable specificity (70.0%); OR: 28.0. In the case of FLUS nodules, the combined criterion (rFNA-V or EU-TIRADS-5) maximized specificity (95.2%) with 57.7% sensitivity and a low percentage (13.9%) of positive nodules, OR: 27.0. In both types of nodules, the low risk category in EU-TIRADS and benign result of rFNA excluded cancer. Concluding, category III nodules with and without nuclear atypia differ in their risk of malignancy and, consequently, diagnostic criteria adopted for the evaluation of these nodules with rFNA and EU-TIRADS should be specific to AUS and FLUS nodules.

Approach to Bethesda system category III thyroid nodules according to US-risk stratification

This study evaluated how to manage Bethesda category III (Bethesda III) (atypia of undetermined significance/follicular lesion of undetermined significance [AUS/FLUS]) thyroid nodules according to the Korean Thyroid Imaging Reporting and Data System (K-TIRADS) to reduce unnecessary surgeries. A total of 161 thyroid nodules diagnosed as Bethesda III underwent surgery from 2016 to 2019. Ultrasonography-guided fine-needle aspiration (US-FNA) or core needle biopsy (CNB) was used for repeat examination. K-TIRADS category was assigned to the thyroid nodules. The proportion of malignancy in Bethesda III nodules confirmed by surgery were significantly increased in proportion relative to K-TIRADS with 60.0% low suspicion, 88.2% intermediate suspicion, and 100% high suspicion nodules (p < 0.001). The proportion of malignancy in AUS and FLUS were significantly different (94.2% vs. 40.0% p = 0.003). The proportion of malignancy in AUS increased with K-TIRADS categories, but there was no difference in FLUS. All K-TIRADS high suspicion nodules were AUS as papillary carcinomas (99%), while 80% of FLUS nodules and 50% of follicular carcinomas showed K-TIRADS low suspicion. In 116 nodules with repeat FNA or CNB after initial Bethesda III results, the conclusive result rate was significantly increased in proportion to K-TIRADS with 58.3% low suspicion, 83.3% intermediate suspicion, and 88.8% high suspicion nodules (p = 0.015). K-TIRADS low suspicion nodules of Bethesda III nodules should be managed after risk-benefit consideration rather than immediate surgery or repeat examination. K-TIRADS for Bethesda III nodules can predict papillary carcinoma well, but not follicular carcinoma.

Atypia of undetermined significance/follicular lesions of undetermined significance: What radiologists need to know

Atypia of undetermined significance/follicular lesions of undetermined significance (AUS/FLUS) refers to an intermediate histologic category of thyroid nodules in The Bethesda System for Reporting Thyroid Cytopathology. Although the risk of malignancy in this category was originally cited as 5-15%, recent literature has suggested higher rates of related malignancy ranging from 38% to 55%. Malignant nodules warrant surgery with total thyroidectomy or thyroid lobectomy, whereas benign nodules can be observed or followed with serial ultrasounds (US) based on their imaging characteristics. The management of nodules with a cytopathologic diagnosis of AUS/FLUS can be difficult because theses nodules lie between the extremes of benign and malignant. The management options for such nodules include observation, repeat fine-needle aspiration, and surgery. The use of molecular genetics, the identification of suspicious US characteristics, and the recognition of additional clinical factors are all important in the development of an appropriate, tailored management approach. Institutional factors also play a crucial role.

Strategy to reduce unnecessary surgeries in thyroid nodules with cytology of Bethesda category III (AUS/FLUS): a retrospective analysis of 667 patients diagnosed by surgery

PURPOSE

Fine-needle aspiration (FNA) is widely used for the diagnosis of thyroid nodules detected by ultrasonography. However, the cytology of atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) often leads to unnecessary thyroid surgery. This study aimed to identify a strategy to reduce unnecessary surgeries in patients with AUS/FLUS nodules.

METHODS

Medical records of 667 patients with the cytology of AUS/FLUS who underwent surgery from January 2007 to December 2017 were retrospectively reviewed. Clinicopathological data were analyzed to identify malignant factors in thyroid nodules with AUS/FLUS. Factors were compared between patients with thyroid cancer and those with benign thyroid nodules, using stepwise multivariate logistic regression and decision tree model.

RESULTS

Pathological thyroid cancer was identified in 193 (43.3%) patients. There was a significant difference in malignancy incidence with respect to family history, number of nodules, number of FNAs, ultrasonographic finding, lymphocytic thyroiditis, and BRAFV600E mutation. Multivariate analysis showed that ultrasonography (K-TIRADS 5) was the most influential independent predictor of malignancy in AUS/FLUS (odds ratio = 11.02, p < 0.001), followed by possessing BRAFV600E mutation (odds ratio = 4.54, p < 0.001). This strategy enabled 226 (89.3%) patients to avoid unnecessary surgeries based on the decision tree model. There was no node of repeated FNA in the decision tree model, which reduced the risk of malignancy (odds ratio = 0.35, p = 0.029).

CONCLUSION

K-TIRADS 5 and BRAFV600E mutation were predictive of malignancy in nodules of AUS/FLUS. These factors should be considered in strategies to reduce unnecessary surgeries for AUS/FLUS.

Cost effectiveness of intraoperative pathology in the management of indeterminate thyroid nodules

Objective This study aims to determine the cost effectiveness of rapid frozen section (RFS) for indeterminate thyroid nodules. Materials and methods A retrospective chart review was conducted between January 2009 and June 2013 at a tertiary care institution. Main outcomes were number needed to treat, RFS efficacy, and cost-savings of avoiding second completion thyroidectomy. Cost-effectiveness was estimated using 2015 Medicare reimbursement rate. Results Out of 1,114 patients undergoing thyroid surgery, 314 had preoperative AUS/FLUS cytopathology and subsequent thyroid lobectomy with RFS. RFS identified 13 of the 32 patients with malignancy resulting in a total thyroidectomy. 19 of the 29 malignancies not detected by RFS were papillary microcarcinomas. Conclusions Completion thyroidectomy was avoided in 1 out of every 24 patients resulting in cost-savings of $ 80.04 per patient. In the era of outpatient thyroid surgery, intraoperative RFS for indeterminate thyroid nodules is cost-effective.

Molecular markers for the classification of cytologically indeterminate thyroid nodules

BACKGROUND

The diagnosis of indeterminate lesions of the thyroid is a challenge in cytopathology practice. Indeed, up to 30% of cases lack the morphological features needed to provide definitive classification. Molecular tests have been developed to assist in the diagnosis of these indeterminate cases. The first studies dealing with the preoperative molecular evaluation of FNA samples focused on the analysis of BRAF^V600E or on the combined evaluation of two or three genetic alterations. The sensitivity of molecular testing was then improved through the introduction of gene panels, which became available for clinical use in the late 2000s. Two different categories of molecular tests have been developed, the 'rule-out' methods, which aim to reduce the avoidable treatment of benign nodules, and the 'rule-in' tests that have the purpose to optimize surgical management. The genetic evaluation of indeterminate thyroid nodules is predicted to improve patient care, particularly if molecular tests are used appropriately and with the awareness of their advantages and weaknesses. The main disadvantage of these tests is the cost, which makes them rarely used in Europe. To overcome this limitation, customized panels have been set up, which are able to detect the most frequent genetic alterations of thyroid cancer.

CONCLUSIONS

In the present review, the most recent available versions of commercial molecular tests and of custom, non-commercial panels are described. Their characteristics and accuracy in the differential diagnosis of indeterminate nodules, namely Bethesda classes III (Atypical follicular lesion of undetermined significance, AUS/FLUS) and IV (Suspicious for follicular neoplasm, FN/SFN) are fully analyzed and discussed.

Ultrasound-guided fine-needle aspiration or core needle biopsy for diagnosing follicular thyroid carcinoma?

OBJECTIVE

We evaluated the preoperative diagnostic values of ultrasound (US), fine-needle aspiration (FNA) and core needle biopsy (CNB) leading to surgery in patients with FTC.

METHODS

From October 1994 to July 2016, 298 patients with FTC who had preoperative US images and underwent US-guided FNA or CNB and surgery were included in this study. We evaluated the results of preoperative FNA or CNB based on the Bethesda system and the US findings according to the Korean thyroid imaging reporting and data system (K-TIRADS).

RESULTS

Predominant US features of FTC showed solid, hypo- or iso-echogenicity, oval smooth margin and halo with no calcification. Based on K-TIRADS, 140 (47.0%) patients with FTC were categorized as low suspicion, 133 (44.63%) as intermediate suspicion and 25 (8.4%) as high suspicion at US. Considering only FNA cytology (n = 230), 6.9% were revealed as Bethesda class I, 16.1% as class II, 37.0% as class III, 29.1% as class IV and 10.9% as class V. Considering the 68 cases with CNB results, 2.9% were revealed as class I, 4.4% as class II, 20.6% as class III and 72.1% as class IV. Despite multiple FNAs, 16.7% of the 84 patients with FTC still obtained Bethesda class I or class II. CNB results in patients with FTC had a significantly higher rate of Bethesda class IV compared to the FNA results (P < .001). FTCs with distant metastasis exhibited a significantly higher rate of Bethesda classes IV and V compared to those without distant metastasis (P = .004).

CONCLUSION

Surgery for FTC is deferred only with preoperative US and FNA. CNB in patients with FTC can lead to surgery better than FNA. Therefore, if the US feature is characteristic and a serially growing large nodule is suspected, the first attempt of CNB may be helpful in selecting a surgical candidate.

Molecular Variants and Their Risks for Malignancy in Cytologically Indeterminate Thyroid Nodules

Background: Gene panels are routinely used to assess predisposition to hereditary cancers by simultaneously testing multiple susceptibility genes and/or variants. More recently, genetic panels have been implemented as part of solid tumor malignancy testing assessing somatic alterations. One example is targeted variant panels for thyroid nodules that are not conclusively malignant or benign upon fine-needle aspiration (FNA). We systematically reviewed published studies from 2009 to 2018 that contained genetic data from preoperative FNA specimens on cytologically indeterminate thyroid nodules (ITNs) that subsequently underwent surgical resection. Pooled prevalence estimates per gene and variant, along with their respective positive predictive values (PPVs) for malignancy, were calculated. Summary: Our systematic search identified 540 studies that were supplemented by 18 studies from bibliographies or personal files. Sixty-one studies met all inclusion criteria and included >4600 ITNs. Overall, 26% of nodules contained at least 1 variant or fusion. However, half of them did not include details on the specific gene, variant, and/or complete fusion pair reported for inclusion toward PPV calculations. The PPVs of genomic alterations reported at least 10 times were limited to BRAF^V600E (98%, 95% confidence interval [CI 96-99%]), PAX8/PPARG (55% [CI 34-78%]), HRAS^Q61R (45% [CI 22-72%]), BRAF^K601E (42% [CI 19-68%]), and NRAS^Q61R (38% [CI 23-55%]). Excluding BRAF^V600E, the pooled PPV for all other specified variants and fusions was 47%. Multiple variants within the same nodule were identified in ∼1% of ITN and carried a cumulative PPV of 77%. Conclusions: The chance that a genomic alteration predicts malignancy depends on the individual variant or fusion detected. Only five alterations were reported at least 10 times; BRAF^V600E had a PPV of 98%, while the remaining four had individual PPVs ranging from 38% to 55%. The small sample size of most variants and fusion pairs found among ITNs, however, limits confidence in their individual PPV point estimates. Better specific reporting of genomic alterations with cytological category, histological subtype, and cancer staging would facilitate better understanding of cancer prediction, and the independent contribution of the genomic profile to prognosis.

Peptide Profile Differences of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features, Encapsulated Follicular Variant, and Classical Papillary Thyroid Carcinoma: An Application of Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging

Introduction: The lack of papillary structures and faint and/or unclear core features of follicular variant of papillary thyroid carcinoma (FV-PTC) may hamper the definitive fine needle aspiration biopsy -based diagnosis. Recently, the nomenclature of noninvasive encapsulated FV-PTC was revised to "noninvasive follicular thyroid neoplasms with papillary-like nuclear features" (NIFTP). However, it remains inconclusive whether or not the peptide patterns differ between NIFTP and encapsulated FV-PTC. The main objectives of this study were to investigate the viability of matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) in the pathological assessment of NIFTP and to evaluate the discriminatory power of MALDI MSI for the classification of classical variant of PTC (CV-PTC), NIFTP, and encapsulated FV-PTC. Methods: MALDI MSI was employed to investigate the changes in peptide profiles from 21 formalin-fixed paraffin-embedded (FFPE) tissue samples (n = 7 from each group of CV-PTC, NIFTP, and FV-PTC). Six out of seven FV-PTC FFPE tissue samples were encapsulated FV-PTC; only one was infiltrative FV-PTC. Liquid chromatography-tandem mass spectrometry was used for the identification of the peptide signals detected in MALDI MSI. Results: Using receiver operating characteristics analysis, 10 peptide signals distinguished NIFTP from normal thyroid parenchyma (area under the curve [AUC] >0.80). To evaluate the discriminatory power of MALDI MSI, statistically significant peptide signals (n = 88) within three groups were used for hierarchical clustering. The method had high discriminatory power for distinguishing CV-PTC from NIFTP and FV-PTC (encapsulated and infiltrative). The majority of the NIFTP and encapsulated FV-PTC were clustered together, indicating that NIFTP could not be distinguished from encapsulated FV-PTC. However, infiltrative FV-PTC FFPE tissue samples had the furthest distance from all the NIFTP cases. High signal intensities of S100-A6, vimentin, and cytoplasmic actin 1 were detected in FV-PTC, prelamin A/C in CV-PTC, and 60S ribosomal protein L6 and L8 in NIFTP tissues. Conclusions: MALDI MSI, a powerful tool combining histological and mass spectrometric data, enabled the differentiation of NIFTP from normal thyroid parenchyma. Although NIFTP is a recent definition that replaces noninvasive encapsulated FV-PTC, the peptide profiles of NIFTP and encapsulated FV-PTC were found to be similar.

USING THE ATA AND ACR TI-RADS SONOGRAPHIC CLASSIFICATIONS AS ADJUNCTIVE PREDICTORS OF MALIGNANCY FOR INDETERMINATE THYROID NODULES

Objective: Thyroid nodules with indeterminate cytology pose management challenges in clinical practice. The aim of this study was to determine the efficacy of ultrasound features in navigating clinical decision making in thyroid nodules with indeterminate cytology. Methods: We retrospectively reviewed ultrasound imaging from 186 adult patients with thyroid nodules and indeterminate cytology who underwent thyroidectomy at a quaternary hospital from 2010-2017. All nodules were classified based on the American Thyroid Association (ATA) and 2017 American College of Radiology Thyroid Imaging Reporting and Data System (ACR TI-RADS). Nodules were included if good quality pre-operative ultrasound imaging and surgical pathology were available. Results: A total of 202 thyroid nodules were included. The median age was 57 years; 82.8% were female. Risk of malignancy (ROM) in resected nodules with Bethesda 3 and 4 cytology was 19.4% and 30.3%, respectively. ATA high-suspicious and TI-RADS 5 nodules had high ROM, 100% in both systems for Bethesda 3 nodules; 66.7% and 50.0%, respectively, for Bethesda 4 nodules. For ATA very-low suspicious/TI-RADS 1 and 2, ROM was 0%. ROM in ATA low-suspicious/TI-RADS 3 nodules with Bethesda 3 cytology was lower (15.2% and 16.0%, respectively) than Bethesda 4 cytology (33.8% and 34.3%, respectively). ATA intermediate-suspicious/TI-RADS 4 nodules with Bethesda 4 cytology had a lower ROM (11.1% and 18.2%, respectively) than Bethesda 3 cytology (28.6 % and 31.6%, respectively). Conclusion: Using either the ATA or the TI-RADS system to risk-stratify nodules with indeterminate cytology may help clinicians plan better for additional diagnostic testing and treatment. Abbreviations: ACR = American College of Radiology; ATA = American Thyroid Association; AUS = atypia of undetermined significance; FLUS = follicular lesion of undetermined significance; FN = follicular neoplasm; PPV = positive predictive value; ROM = risk of malignancy; SFN = suspicious for follicular neoplasm; TI-RADS = Thyroid Imaging Reporting and Data System.

Diagnostic Performance of Ultrasound Patterns by K-TIRADS and 2015 ATA Guidelines in Risk Stratification of Thyroid Nodules and Follicular Lesions of Undetermined Significance

OBJECTIVE. The objective of our study was to assess the malignancy rates of thyroid nodules in the cytologically determined subclass of atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS) and to assess the diagnostic performance of ultrasound (US) patterns defined by the Korean Thyroid Imaging Reporting and Data System (K-TIRADS) and the 2015 American Thyroid Association (ATA) guidelines for risk stratification of AUS/FLUS nodules. MATERIALS AND METHODS. From January 2010 to December 2016, 1340 thyroid nodules were diagnosed as AUS/FLUS via fine-needle aspiration biopsy. Of these, 683 cytopathologically confirmed nodules were included in this study. Each nodule was assigned to a category and US pattern, as defined by the K-TIRADS and ATA guidelines. US patterns were compared between benign and malignant nodules, and malignancy rates were calculated according to the subclasses of AUS/FLUS nodules and the K-TIRADS and ATA guidelines. Predictors of malignancy were assessed using logistic regression analysis. RESULTS. The overall malignancy rate of AUS/FLUS nodules was 47.4% (324/683). There were significant differences in malignancy risk among the subclasses (p = 0.001). There were significant differences in malignancy rates according to US patterns, K-TIRADS categories, and ATA categories (p < 0.001). The malignancy rates in the K-TIRADS categories of benign, low, intermediate, and high suspicion were 0%, 1.99%, 34.66%, and 89.00%, respectively (p < 0.001). The malignancy rates in the ATA categories of benign, very low, low, intermediate, and high suspicion were 0%, 0%, 3.33%, 33.54%, and 87.67% (p < 0.001). CONCLUSION. AUS/FLUS nodules with a final diagnosis of malignancy had significantly higher rates of suspicious US features and different K-TIRADS and ATA categories than benign nodules. US categories by K-TIRADS and ATA guidelines can be useful in predicting malignancy and risk stratification, and management planning can be adjusted according to US pattern.

An Insight into the Utility of Sub-Categorisation of Atypia of Undetermined Significance for Risk Stratification: A Retrospective Study on an Indian Cohort with Histopathological Correlation

BACKGROUND

Atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS) criterion in thyroid fine-needle aspirates (FNAs) has been a heterogeneous entity with much inter-observer variation. Sub-categorisation of AUS/FLUS has been observed to play an effective role in risk stratification. We aimed to validate AUS/FLUS sub-categorisation in correlation with the spectrum of malignancy.

STUDY DESIGN

Subjects included patients with AUS/FLUS diagnosed between January 2015 and December 2016. AUS/FLUS cases were sub-categorised into those exhibiting (1) architectural atypia, (2) cytological atypia, (3) architectural and cytological atypia, (4) AUS with Hürthle cells, and (5) AUS not otherwise specified (AUS-NOS). Each sub-category was correlated with their corresponding incidence of malignancy in surgical resections.

RESULT

The overall incidence of AUS/FLUS in our centre was 13% (132/1,018). On retrospective review of 117 patients with AUS/FLUS, smears with cytological atypia showed a higher incidence of malignancy (78.3%) than those with architectural atypia (75.3%). AUS/FLUS cases with both cytological and architectural atypia had a malignancy rate of 71.4%.

CONCLUSION

AUS/FLUS cases with cytological atypia had a higher risk of malignancy than those with architectural atypia. The sub-categorisation of AUS/FLUS is diagnostically important for the proper risk stratification of patients.

Validation of web-based thyroid imaging reporting and data system in atypia or follicular lesion of undetermined significance thyroid nodules

BACKGROUND

Atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) show variable malignancy risk. We validated the web-based predictive models and the scoring system by the American College of Radiology (ACR) for AUS/FLUS nodules to stratify the malignancy risk.

METHODS

From January 2011 to November 2014, 275 consecutive nodules diagnosed as AUS/FLUS were enrolled. The discrimination and calibration ability of a web-based scoring with inclusion of biopsy result and sonographic features, old web-based scoring model without biopsy result, and ACR models were assessed.

RESULTS

The areas under the receiver operating characteristic curve of the validation set were 0.670 for the new web-based model, 0.710 for the old web-based model, and 0.732 for the ACR scoring risk-stratification model. All models were well calibrated.

CONCLUSION

The web-based scoring risk-stratification model using the combined information of ultrasonography features and biopsy result for AUS/FLUS nodules to stratify malignancy risk presents an acceptable predictive accuracy.

Cytomorphologic, Imaging, Molecular Findings, and Outcome in Thyroid Follicular Lesion of Undetermined Significance/Atypical Cell of Undetermined Significance (AUS/FLUS): A Mini-Review

OBJECTIVES

Since the introduction of the entity of "Atypical cell of undetermined significance /follicular lesion of undetermined significance" (AUS/FLUS) by The Bethesda System for Reporting Thyroid Cytology (TBSRTC) in 2007, there have been many published studies about the cytomorphologic criteria, subclassification, outcome, and management of patients with the diagnosis of AUS/FLUS. There have been many studies in different aspects of this indeterminate category, i.e., cytologic and molecular findings, ultrasonographic findings, and in some instances even core-needle biopsy to address a better and safer way of the management of patients with this fine-needle aspiration cytology diagnosis. The second edition of TBSRTC and the 2015 American Thyroid Association guidelines provide an update on the follow-up and management of AUS/FLUS. A multidisciplinary team consisting of pathologists, endocrinologists, surgeons, and radiologists should be involved in the diagnosis and management of AUS/FLUS, and all of them should be aware of the heterogeneity of this lesion for the prediction of the treatment and outcome.

STUDY DESIGN

In this review, we consider different research platforms (2008-2017) to find the best and key reports for the above-mentioned challenging aspects of AUS/FLUS.

CONCLUSION

AUS/FLUS is now a well-defined group of thyroid lesions, which can be most accurately diagnosed and managed with cytomorphology, molecular, and ancillary studies.

Both Ultrasound Features and Nuclear Atypia are Associated with Malignancy in Thyroid Nodules with Atypia of Undetermined Significance

BACKGROUND

The optimal management of thyroid nodules that undergo fine-needle aspiration (FNA) with findings of atypia of undetermined significance (AUS) is unclear. Categorizing nodules by AUS subtype and ultrasound characteristics may improve risk stratification. Therefore, the purpose of this study is to evaluate the association between AUS subtype and ultrasound features on risk of malignancy (ROM).

METHODS

We performed a review of all patients with a thyroid nodule who underwent an FNA at our institution between January 2010 and November 2015. Patients with AUS were divided into groups with (1) nuclear atypia, (2) architectural atypia, or (3) Hurthle cell atypia. Their ultrasound features were assessed using the American Thyroid Association (ATA) thyroid nodule sonographic patterns. We conducted a univariate and multivariable analysis to determine the association between AUS subtype and other variables of interest with ROM.

RESULTS

Of the 3428 thyroid nodules that underwent FNA, 237 (6.9%) had AUS. Of the 97 surgically resected nodules, 67 (69%) were benign and 30 (31%) were malignant. On univariate analysis nuclear atypia (p < 0.01) was associated with a thyroid malignancy. On multivariable analysis, both ATA high-risk ultrasound features (p = 0.04, odds ratio [OR] 3.68) and nuclear atypia (p < 0.01, OR 11.8) were independently associated with a final diagnosis of thyroid carcinoma.

CONCLUSIONS

Nuclear atypia and ATA high-risk ultrasound features are useful in identifying patients with AUS that are at a higher risk of thyroid malignancy. Surgeons should take these factors into consideration when evaluating patients with AUS.

Utility of including BRAF mutation analysis with ultrasonographic and cytological diagnoses in ultrasonography-guided fine-needle aspiration of thyroid nodules

This study investigated the role of BRAF mutation analysis in thyroid fine-needle aspiration (FNA) samples compared to ultrasonographic and cytological diagnoses. A total 316 patients underwent ultrasonography (US)-guided FNA with BRAFV600E mutation analysis to diagnose thyroid nodules. One hundred sixteen patients with insufficient US images (n = 6), follow-up loss (n = 43), or unknown final diagnosis (n = 67) were excluded from the study. Comparisons between US diagnoses, cytological diagnoses, and BRAF mutation analysis were performed. Of 200 thyroid nodules, there was US diagnosis with 1 false negative and 11 false positive cases, cytological diagnosis with 10 false negative and 2 false positive cases, and BRAFV600E mutation analysis with 19 false negative and 2 false positive cases. The sensitivity, specificity, positive and negative predictive values, and accuracy of BRAFV600E mutation analysis were 83.2%, 98.1%, 97.5%, 86.6%, and 91%, respectively. Of the 18 nodules with Bethesda category III, 9 were true positive, 6 were true negative, 3 was a false negative, and none were false positive on BRAF mutation analysis. In conclusion, we recommend that BRAFV600E mutation analysis only be performed for evaluating thyroid nodules with Bethesda category III, regardless of US diagnosis.

Thyroid Nodules with Indeterminate Cytology: Utility of the American Thyroid Association Sonographic Patterns for Cancer Risk Stratification

BACKGROUND

The 2015 American Thyroid Association (ATA) guidelines recommend using a classification based on sonographic patterns to set the size threshold for biopsies. Each pattern is associated with a distinct estimated rate of malignancy that it was hypothesized should stratify the risk of malignancy of cytologically indeterminate thyroid nodules (ITNs).

METHODS

Ultrasound images of 463 ITNs (38% atypia/follicular lesions of undetermined significance; 62% follicular neoplasms) with histological follow-up consecutively evaluated between October 2008 and June 2015 at the authors' academic cancer center were independently evaluated by three observers and classified into one of the five sonographic patterns proposed by the ATA. Nodules with sonographic patterns not defined in the classification were grouped into a non-ATA pattern category. Differences in clinical and histological findings between the sonographic patterns were assessed. The prevalence of malignancy and odds ratio for malignancy were calculated for each sonographic pattern (low and intermediate patterns were collapsed for the analysis).

RESULTS

The distribution of size and cytological diagnosis was significantly different between sonographic patterns (p < 0.001). The overall rate of malignancy was 27%. The rate of malignancy for the very low, low/intermediate, high, and non-ATA patterns were 0%, 19%, 56%, and 36%, respectively, and were all significantly different. Compared to the low/intermediate suspicion patterns, the odds ratios for malignancy were 2.35 for the non-ATA and 5.18 for the high suspicion patterns (p < 0.001). The odds ratio of the non-ATA pattern was 0.45 over the high suspicion pattern (p = 0.04). Results were similar in both cytological categories and for each observer separately. Sonographic patterns were associated with distinct histopathological profiles (p < 0.001).

CONCLUSIONS

ATA sonographic patterns are associated with distinct clinical features and pathological outcomes, and effectively stratify the cancer risk in ITNs. Thus, the ATA sonographic patterns should be used not only to set the size threshold for biopsy, but also to personalize management after the biopsy.

Evaluation and Management of Indeterminate Thyroid Nodules: The Revolution of Risk Stratification Beyond Cytological Diagnosis

In accordance with National Guidelines, we currently follow a linear approach to the diagnosis of thyroid nodules, with management decision based primarily on a cytological diagnosis following fine-needle aspiration biopsy. However, 25% of these biopsies render an indeterminate cytology, leaving uncertainty regarding appropriate management. Individualizing the risk of malignancy of these nodules could improve their management significantly. We summarize the current evidence on the relevance of clinical information, radiological features, cytological features, and molecular markers tests results and describe how these can be integrated to personalize the management of thyroid nodules with indeterminate cytology. Several factors can be used to stratify the risk of malignancy in thyroid nodules with indeterminate cytology. Male gender, large tumors (>4 cm), suspicious sonographic patterns, and the presence of nuclear atypia on the cytology are all associated with an increased cancer prevalence. The added value of current molecular markers in the risk stratification process needs further study because their performance seems compromised in some clinical settings and remains to be validated in others. Risk stratification is possible in thyroid nodules with indeterminate cytology using data that are often underused by current guidelines. Future guidelines should integrate these factors and personalize the recommended diagnostic and therapeutic approaches accordingly.

Diagnostic Utility of Molecular and Imaging Biomarkers in Cytological Indeterminate Thyroid Nodules

Indeterminate thyroid cytology (Bethesda III and IV) corresponds to follicular-patterned benign and malignant lesions, which are particularly difficult to differentiate on cytology alone. As ~25% of these nodules harbor malignancy, diagnostic hemithyroidectomy is still custom. However, advanced preoperative diagnostics are rapidly evolving.This review provides an overview of additional molecular and imaging diagnostics for indeterminate thyroid nodules in a preoperative clinical setting, including considerations regarding cost-effectiveness, availability, and feasibility of combining techniques. Addressed diagnostics include gene mutation analysis, microRNA, immunocytochemistry, ultrasonography, elastosonography, computed tomography, sestamibi scintigraphy, [18F]-2-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET), and diffusion-weighted magnetic resonance imaging.The best rule-out tests for malignancy were the Afirma® gene expression classifier and FDG-PET. The most accurate rule-in test was sole BRAF mutation analysis. No diagnostic had both near-perfect sensitivity and specificity, and estimated cost-effectiveness. Molecular techniques are rapidly advancing. However, given the currently available techniques, a multimodality stepwise approach likely offers the most accurate diagnosis, sequentially applying one sensitive rule-out test and one specific rule-in test. Geographical variations in cytology (e.g., Hürthle cell neoplasms) and tumor genetics strongly influence local test performance and clinical utility. Multidisciplinary collaboration and implementation studies can aid the local decision for one or more eligible diagnostics.

Malignancy Risk and Related Factors of Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance in Thyroid Fine Needle Aspiration

Atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) in thyroid fine needle aspiration (FNA) is a challenging category. The malignancy risk is different by multiple factors and subsequent management strategy is inconclusive. Therefore, we analyzed the malignancy risk of AUS/FLUS according to radiological and clinical features. A total of 687 nodules that had been initially diagnosed as AUS/FLUS were retrospectively reviewed from 6365 thyroid FNAs between 2011 and 2014. The ultrasonographic (US) features were categorized using the Korean Thyroid Imaging Reporting and Data System. Radiological and clinical features were compared according to the second FNA results or histologically confirmed results from surgery. Repeat FNA was performed on 248 (36%) nodules, and 49 (7%) nodules underwent immediate surgery. Among the 248 nodules subjected to repeated FNA, 49 (20%) nodules were diagnosed again as AUS/FLUS, 123 (50%) were found to be benign, and 47 (19%) were diagnosed as follicular neoplasm, suspicious for malignancy or malignant. Among histologically confirmed nodules, the US features were more unfavorable in malignant nodules, and hypo- or anechogenicity was associated with a higher risk of malignancy after adjusting for age, size, and other US features (P < 0.01). In conclusion, we observed that malignant nodules tended to show unfavorable US features, especially hypo- or anechogenicity. Age, sex, and thyroid function were not significantly associated with malignancy risk. We also found out that malignancy risk was not different between the group which underwent immediate operation following the AUS/FLUS diagnosis and the group which underwent repeated FNA after the initial diagnosis.

Papillary Thyroid Carcinoma Arising Within a Follicular Adenoma: A Case Report, Ultrasound Features, and Considerations

Papillary thyroid carcinoma (PTC) arising within a follicular adenoma is an exceptionally rare histopathological subtype that shows the nuclear features of PTC within a benign-appearing, circumscribed follicular adenoma. Although it is clinically significant because of its malignant nature, its ultrasonographic features have not been described previously. A 26-year-old man presented with a heterogeneous isoechoic solid nodule with a marked hypoechoic solid focus and a low echoic peripheral rim in the right thyroid gland on ultrasonography. On color Doppler images, markedly increased vascularity was seen in the hypoechoic solid component. An ultrasound-guided gun biopsy suggested a follicular neoplasm. In the evaluation of a hemithyroidectomy specimen, thyroid follicles and a thin fibrous capsule were seen, which favored a follicular adenoma with tumor cells in a focal area indicating papillary carcinoma. Here, we report a case of PTC arising within a follicular adenoma and discuss possible considerations in thyroid ultrasonographic examinations.

Validation of American Thyroid Association Ultrasound Risk Assessment of Thyroid Nodules Selected for Ultrasound Fine-Needle Aspiration

OBJECTIVE

The aim of this study was to validate the American Thyroid Association (ATA) sonographic risk assessment of thyroid nodules.

METHODS

The ATA sonographic risk assessment was prospectively applied to 206 thyroid nodules selected for ultrasound-guided fine-needle aspiration (US-FNA), and analyzed with The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC), as well as surgical pathology for the subset undergoing surgical excision.

RESULTS

The analysis included 206 thyroid nodules averaging 2.4 cm (range 1-7 cm; standard error of the mean 0.07). Using the ATA US pattern risk assessment, nodules were classified as high (4%), intermediate (31%), low (38%), and very low (26%) risk of malignancy. Nodule size was inversely correlated with sonographic risk assessment, as lower risk nodules were larger on average (p < 0.0001). Malignancy rates determined by cytology/surgical pathology were high 100%, intermediate 11%, low 8%, and very low 2%, which were closely aligned with ATA malignancy risk estimates (high 70-90%, intermediate 10-20%, low 5-10%, and very low 3%). ATA US pattern risk assessment also appropriately predicted the proportion of nodules classified as malignant or suspicious for malignancy through TBSRTC classification-high (77%), intermediate (6%), low (1%), and very low 0%-as well as benign TBSRTC classification-high (0%), intermediate (47%), low (61%), and very low (70%) (p < 0.0001). Malignancy rates of surgically excised, cytologically indeterminate nodules followed ATA sonographic risk stratification (high 100%, intermediate 21%, low 17%, and very low 12%; p = 0.003).

CONCLUSION

This prospective study supports the new ATA sonographic pattern risk assessment for selection of thyroid nodules for US-FNA based upon TBSRTC and surgical pathology results. In the setting of indeterminate cytopathology, nodules categorized as atypia of undetermined significance/follicular lesion of undetermined significance with ATA high-risk sonographic patterns have a high likelihood of being malignant.

Risk Stratification of Thyroid Nodules With Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance (AUS/FLUS) Cytology Using Ultrasonography Patterns Defined by the 2015 ATA Guidelines

PURPOSE

The purpose of this study was to evaluate the predictive value of ultrasonography (US) patterns based on the 2015 American Thyroid Association (ATA) guidelines for malignancy in atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS) nodules.

METHODS

From January 2014 to August 2015, 133 thyroid nodules that were initially diagnosed as AUS/FLUS on fine needle aspiration (FNA) were included in this study. Each nodule was assigned a category with US patterns defined by the ATA guidelines. Clinical characteristics and US patterns were compared between the benign and malignant nodules, and malignancy rates were calculated according to the ATA guidelines.

RESULTS

The malignancy rate in the very low suspicion group was 0.0% in AUS/FLUS nodules. When applying the ATA guidelines, significant differences existed for US patterns between the benign and malignant nodules in the AUS group ( P = .032) but not the FLUS group ( P = .168).

CONCLUSIONS

Ultrasonography patterns by the 2015 ATA guidelines can provide risk stratification for nodules with AUS cytology but not for ones with FLUS cytology. For nodules with AUS/FLUS cytology with the very low suspicion pattern of the ATA guidelines, follow-up US might be recommended instead of repeat FNA.

Cytology-Ultrasonography Risk-Stratification Scoring System Based on Fine-Needle Aspiration Cytology and the Korean-Thyroid Imaging Reporting and Data System

BACKGROUND

The malignancy risk of a cytology diagnosis may depend on the ultrasonography (US) patterns of thyroid nodules, and management should be determined by the combined malignancy risk of fine-needle aspiration (FNA) cytology and US patterns. This study was performed to develop a clinically applicable cytology-ultrasonography (CU) scoring system for malignancy risk stratification based on FNA cytology and US patterns, according to the Korean-Thyroid Imaging Reporting and Data System (K-TIRADS).

METHODS

This retrospective Institutional Review Board-approved study included 1651 thyroid nodules (≥1 cm) with final diagnoses. The malignancy risk was assessed of the combined results of FNA cytology and the K-TIRADS for the development of the CU system. The interaction between FNA cytology and US pattern (K-TIRADS) in the malignancy risk of nodules was investigated by using a binominal test.

RESULTS

The malignancy risk of nodules could be stratified into four CU scores (very low risk, <3%; low risk, ≥3%, <30%; high risk, ≥30%, <90%; very high risk, ≥90%). In nodules with non-diagnostic, benign, and atypia of undetermined significance/follicular lesion of undetermined significance cytology results, low-suspicion US pattern (K-TIRADS 3) significantly decreased the malignancy risk of nodules (p = 0.003, 0.013, and 0.027, respectively), and a high-suspicion US pattern (K-TIRADS 5) significantly increased the malignancy risk of nodules (p ≤ 0.001). A Bethesda 1 or 4 cytology result did not significantly change the malignancy risk of any K-TIRADS (p ≥ 0.518 and p ≥ 0.137, respectively). A Bethesda 2 cytology result decreased and a Bethesda 5 or 6 cytology result increased the malignancy risk of K-TIRADS 3, 4, and 5 (p ≤ 0.001). A Bethesda 3 cytology result increased the malignancy risk of K-TIRADS 3 and 4 (p < 0.001 and p = 0.024, respectively).

CONCLUSION

The malignancy risk of thyroid nodules can be stratified by the CU risk-stratification system, based on FNA cytology and the K-TIRADS. The proposed CU scoring system may be helpful in the management of thyroid nodules after FNA.

Diagnostic accuracy of Thyroid Imaging Reporting and Data System in the prediction of malignancy in nodules with atypia and follicular lesion of undetermined significance cytologies

OBJECTIVE

Thyroid Imaging Reporting and Data System (TIRADS) is a simple and reliable reporting system for the prediction of malignancy. We aimed to determine the role of TIRADS in the prediction of malignancy in subcategories of Bethesda Category III, atypia of undetermined significance (AUS) and follicular lesion of undetermined significance (FLUS).

DESIGN & PATIENTS

A total of 461 nodules with AUS cytology in 450 patients and 179 nodules with FLUS cytology in 168 patients were included. Ultrasonography (US) features and postoperative histopathology results were documented. Every suspicious US feature was scored as 1 and 0 according to the presence or not, respectively. TIRADS category of each nodule was determined.

RESULTS

In AUS subcategory, histopathologically malignant nodules had significantly different TIRADS categories compared to benign nodules (P = 0·001), but this was not the case in FLUS subcategory (P = 0·121). In AUS group, malignant nodules had significantly higher prevalance of microcalcification, hypoechogenicity and anteroposterior/transverse ratio than benign ones (P < 0·001, P < 0·001 and P = 0·003, respectively) and TIRADS categories of 4c and 5 were more frequent in malignant nodules (P < 0·05). Microcalcification, hypoechogenicity and TIRADS were found to be associated with malignancy in multivariate logistic regression analysis in this subcategory. TIRADS category ≥4c was associated with malignancy (AUC ± SE: 0·584 ± 0·028). In FLUS subcategory, there was no significant difference between histopathologically malignant and benign nodules with respect to suspicious US features (P > 0·05, all).

CONCLUSION

TIRADS seems to be useful in predicting malignancy and planning further management in the AUS subcategory, but not quite so in the FLUS subcategory.

The predictive value of sonographic images of follicular lesions - a comparison with nodules unequivocal in FNA - single centre prospective study

BACKGROUND

To determine the diagnostic efficacy of ultrasonographic malignancy risk features (UMRFs) in follicular lesions (FL) in a population with low risk of malignancy in FL and to compare it with a similar analysis in a group of patients with unequivocal cytology (UC): benign lesion (BL) or malignant neoplasm (MN).

METHODS

Presence of UMRFs (hypoechogenicity, solid echostructure, taller-than-wide shape, pathological vascularization, irregular margins, microcalcifications and macrocalcifications) and their sets were assessed in 322 FL: 202 follicular lesions of undetermined significance (FLUS) and 120 suspicious for follicular neoplasm (SFN) and 300 nodules with UC: 200 BL and 100 MN, subsequently evaluated histopathologically.

RESULTS

Cancers were confirmed in 100% nodules in MN group (89.0% of them were papillary carcinomas - PTC), in 6.4% FLUS nodules (69.2% PTC), and in 10.8% SFN nodules (30.8% PTC). In the UC group all UMRFs occurred more frequently in cancers than in benign lesions. In the FL group only calcifications were found in cancers more frequently - macro and microcalcifications together: 34.6 vs. 11.5% (p = 0.001) and isolated macrocalcifications: 26.0 vs. 6.8% (p = 0.001); the presence of those features increased the basic risk of malignancy in FL more than 2 times. The presence of at least 2 of the following URMFs: hypoechogenicity, solid echostructure, any type of calcifications and suspected shape, additionally improved sensitivity.

CONCLUSIONS

Evaluation of UMRFs in FLs is less effective than in nodules with UC, and its effectiveness decreases parallel to the decrease in percentage of PTCs among malignant neoplasms and to the increase of the percentage of adenomas among benign nodules. The presence of macrocalcifications in such FLs significantly increases the basic risk of malignancy in these nodules.

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.

Ultrasonography Diagnosis and Imaging-Based Management of Thyroid Nodules: Revised Korean Society of Thyroid Radiology Consensus Statement and Recommendations

The rate of detection of thyroid nodules and carcinomas has increased with the widespread use of ultrasonography (US), which is the mainstay for the detection and risk stratification of thyroid nodules as well as for providing guidance for their biopsy and nonsurgical treatment. The Korean Society of Thyroid Radiology (KSThR) published their first recommendations for the US-based diagnosis and management of thyroid nodules in 2011. These recommendations have been used as the standard guidelines for the past several years in Korea. Lately, the application of US has been further emphasized for the personalized management of patients with thyroid nodules. The Task Force on Thyroid Nodules of the KSThR has revised the recommendations for the ultrasound diagnosis and imaging-based management of thyroid nodules. The review and recommendations in this report have been based on a comprehensive analysis of the current literature and the consensus of experts.

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.

2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer

BACKGROUND

Thyroid nodules are a common clinical problem, and differentiated thyroid cancer is becoming increasingly prevalent. Since the American Thyroid Association's (ATA's) guidelines for the management of these disorders were revised in 2009, significant scientific advances have occurred in the field. The aim of these guidelines is to inform clinicians, patients, researchers, and health policy makers on published evidence relating to the diagnosis and management of thyroid nodules and differentiated thyroid cancer.

METHODS

The specific clinical questions addressed in these guidelines were based on prior versions of the guidelines, stakeholder input, and input of task force members. Task force panel members were educated on knowledge synthesis methods, including electronic database searching, review and selection of relevant citations, and critical appraisal of selected studies. Published English language articles on adults were eligible for inclusion. The American College of Physicians Guideline Grading System was used for critical appraisal of evidence and grading strength of recommendations for therapeutic interventions. We developed a similarly formatted system to appraise the quality of such studies and resultant recommendations. The guideline panel had complete editorial independence from the ATA. Competing interests of guideline task force members were regularly updated, managed, and communicated to the ATA and task force members.

RESULTS

The revised guidelines for the management of thyroid nodules include recommendations regarding initial evaluation, clinical and ultrasound criteria for fine-needle aspiration biopsy, interpretation of fine-needle aspiration biopsy results, use of molecular markers, and management of benign thyroid nodules. Recommendations regarding the initial management of thyroid cancer include those relating to screening for thyroid cancer, staging and risk assessment, surgical management, radioiodine remnant ablation and therapy, and thyrotropin suppression therapy using levothyroxine. Recommendations related to long-term management of differentiated thyroid cancer include those related to surveillance for recurrent disease using imaging and serum thyroglobulin, thyroid hormone therapy, management of recurrent and metastatic disease, consideration for clinical trials and targeted therapy, as well as directions for future research.

CONCLUSIONS

We have developed evidence-based recommendations to inform clinical decision-making in the management of thyroid nodules and differentiated thyroid cancer. They represent, in our opinion, contemporary optimal care for patients with these disorders.

Relationship Between Sonographic Characteristics and Afirma Gene Expression Classifier Results in Thyroid Nodules With Indeterminate Fine-Needle Aspiration Cytopathology

OBJECTIVE

The purpose of this article is to investigate whether specific clinical and sonographic characteristics are predictive of a benign Afirma test result.

MATERIALS AND METHODS

We conducted a retrospective study of Afirma gene expression classifier analysis performed in 44 patients with 45 indeterminate thyroid fine-needle aspiration (FNA) cytologic results between March 2013 and April 2014. Of these, 33 of 45 nodules (73.3%) were repeat atypia of undetermined significance (AUS) and follicular lesions of undetermined significance (FLUS), or follicular neoplasm (FN) and suspicious for a follicular neoplasm (SFN) before Afirma testing.

RESULTS

Of the 45 nodules, 21 (46.7%) were cytologically diagnosed as FLUS, 16 (35.6%) were diagnosed as AUS, and eight (17.8%) were diagnosed as FN or SFN. By Afirma testing, 23 of the 45 nodules (51.1%) were benign, 21 (46.7%) were suspicious, and one (2.2%) had nondiagnostic results. The mean (± SD) nodule size was smaller in the Afirma-benign group than in the Afirma-suspicious group (1.8 ± 0.8 cm [95% CI, 1.4-2.1] vs 2.2 ± 0.8 cm [95% CI, 1.8-2.6]; p < 0.035). No sonographic feature was statistically significantly different between the Afirma-benign and -suspicious groups, including nodule solidity (p = 0.225), echogenicity (p = 0.543), calcification (p = 0.542), and hypervascularity (p = 0.976). All nodules were ovoid shaped and had circumscribed margins in both Afirma groups.

CONCLUSION

Smaller nodule size was the only characteristic associated with a benign diagnosis on Afirma testing. Sonographic characteristics are not helpful in cases that had a repeat indeterminate FNA finding before Afirma testing.

Association Between Obesity and BRAFV600E Mutation Status in Patients with Papillary Thyroid Cancer

BACKGROUND

The prevalence of papillary thyroid cancer (PTC) is thought to be related to obesity, which affects the prognosis for PTC patients. However, the mechanisms implicated in the relationship between obesity and PTC is a matter for debate. In this study, we aimed to gain insight into the relationship between obesity and the clinicopathological features of PTC, including the BRAFV600E mutation.

METHODS

The medical records of 1121 PTC patients were reviewed and the relationships between anthropometric factors, biochemical parameters, and clinicopathological parameters, including BRAFV600E mutation status, were analyzed.

RESULTS

Body mass index (BMI) showed a strong association with advanced TNM stage (p < 0.001) and BRAFV600E mutation status (p = 0.008). We also found that BRAFV600E (+) patients had a higher body weight (p = 0.024) and a higher BMI (p = 0.003) than patients with BRAFV600E (-) PTC. In addition, BRAFV600E (+) PTC patients had a significantly higher incidence of extrathyroidal extension (p = 0.025) and more advanced T, N, TNM stage (p < 0.001) than BRAFV600E (-) PTC patients. Consistent with this observation, female BRAFV600E (+) PTC patients had a higher BMI (p = 0.011) and more aggressive tumor behaviors than female BRAFV600E (-) PTC patients. In multivariate analysis, BMI was persistently associated with BRAFV600E mutation in the entire cohort (odds ratio [OR] 1.387; 95 % CI 1.036-1.859; p = 0.028) and in the female subcohort (OR 1.221; 95 % CI 1.014-1.631; p = 0.046).

CONCLUSION

The positive association between BMI and BRAFV600E supports the hypothesis that excessive bodyweight influences tumor progression.

RAS Mutations in AUS/FLUS Cytology: Does it Have an Additional Role in BRAFV600E Mutation-Negative Nodules?

The object of this study is to evaluate the additional role of RAS mutation in detecting thyroid malignancy among BRAF mutation-negative nodules diagnosed as atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) on cytology.From December 2009 to December 2011, 202 BRAF mutation-negative thyroid nodules diagnosed as AUS/FLUS cytology in 201 patients were included in this study. RAS mutation analysis was performed using residual material from ultrasonography-guided fine needle aspiration (US-FNA) cytology testing for K-RAS, N-RAS, and H-RAS codons 12/13 and 61 point mutations. The authors evaluated the association between RAS mutation status and cytopathologic characteristics.Of the 202 BRAF mutation-negative thyroid nodules with AUS/FLUS cytology, 4 were considered insufficient for mutation analysis. Of the 198 thyroid nodules, 148 (74.7%) were confirmed as benign and 50 (25.3%) as malignant. Thirty-one (15.7%) of the 198 thyroid nodules were positive for any RAS mutation, 4 positive for K-RAS 12/13, 26 for N-RAS 61, and 1 positive for H-RAS 61. Seven (22.6%) of the RAS mutation positive nodules were malignant, 1 with K-RAS 12/13, 6 with N-RAS 61. Twenty-four (77.4%) of the 31 nodules positive for K-RAS 12/13 (N = 3), N-RAS 61 (N = 20), or H-RAS 61 (N = 1) mutations were proven benign. None of the 198 thyroid nodules were positive for K-RAS 61, N-RAS 12/13, or H-RAS 12/13 mutations.N-RAS 61 mutation is the most common mutation detected among BRAF mutation-negative nodules with AUS/FLUS cytology. RAS mutation has limited value in predicting malignancy among BRAF mutation-negative thyroid nodules with AUS/FLUS cytology and further, investigation is anticipated to evaluate the true role of RAS mutation in thyroid malignancy.

Malignancy risk and characteristics of thyroid nodules with two consecutive results of atypia of undetermined significance or follicular lesion of undetermined significance on cytology

PURPOSE

To evaluate the malignancy risk and characteristics of thyroid nodules with two "Atypia of Undetermined Significance" or "Follicular Lesion of Undetermined Significance" (AUS/FLUS) results, and compare characteristics of malignancies with two AUS/FLUS results to those with one AUS/FLUS result.

METHODS

Of 441 thyroid nodules with initial AUS/FLUS results, 236 underwent repeat fine-needle-aspiration (FNA), with 58 obtaining repeated AUS/FLUS results. Thyroid Imaging Reporting and Data System (TIRADS) categories were assigned, and clinico-pathological characteristics were compared between benign and malignant nodules and between malignancies with two consecutive AUS/FLUS results and those with one AUS/FLUS result.

RESULTS

Thirty-one percent (18/58) of nodules with two AUS/FLUS results and 58.1% (18/31) of confirmed nodules were malignant. Age, gender, nodule size, ultrasound features and TIRADS categories did not differ between benign and malignant nodules or between malignancies with one and two AUS/FLUS results. Malignancies with two AUS/FLUS results had a higher proportion of a follicular variant of papillary thyroid carcinoma (PTC) (46.7% vs. 13.6%, P = 0.009).

CONCLUSIONS

Thyroid nodules with two AUS/FLUS results had a high malignancy risk of at least 31.0% and a higher proportion of a follicular variant of PTC. Surgery should be considered regardless of ultrasound features.

KEY POINTS

• Thyroid nodules with two consecutive AUS/FLUS results had a high malignancy risk. • Ultrasound features are less useful in nodules with two AUS/FLUS results. • The follicular variant of PTC is more frequent in malignancies with two AUS/FLUS results.

Clinical presentation of patients with a thyroid follicular neoplasm: are there preoperative predictors of malignancy?

BACKGROUND

Studies examining differences in presentation of patients with benign [follicular adenoma (FA)] and malignant follicular thyroid neoplasms [follicular thyroid carcinoma (FTC) or follicular variant papillary thyroid carcinoma (FVPTC)] include only one or two of these subtypes, and none has considered clinical, cytological, and sonographic features together. We therefore examined presenting clinical features of all benign and malignant follicular neoplasm subtypes in an attempt to identify predictors of malignancy.

METHODS

Consecutive patients with a surgically resected follicular thyroid neoplasm at a tertiary hospital from 2005 to 2013 were reviewed. Age, gender, symptoms, history, physical findings, nodule size, sonographic, cytologic, and final pathologic results were recorded. Multivariate logistic regression was used to determine variables that contributed to a diagnosis of malignant follicular neoplasm.

RESULTS

A total of 616 patients (163 males, 453 females) presented with 441 FAs, 17 FTCs, and 158 FVPTCs. On multivariate analysis, male sex [odds ratio (OR) 1.87, p = 0.008], family history of thyroid cancer (OR 5.16, p < 0.001), and history of head and neck radiation (OR 2.01, p = 0.04) were associated with an increased odds of malignancy; age >45 (OR 2.03, p = 0.001), dysphagia (OR 3.48, p = 0.001) or pressure sensation (OR 3.00, p = 003), concomitant hyperthyroidism (OR 4.76, p = 0.01), nodules ≥4 cm (OR 3.68, p < 0.001), and multinodularity on physical examination (OR 1.93, p = 0.004) were associated with an increased odds of a benign lesion.

CONCLUSIONS

Independent clinical predictors exist that might be helpful in preoperative differentiation of benign and malignant follicular neoplasms. A combination of these predictors with both FNA and molecular results may help us to improve the clinical management of patients with follicular thyroid lesions.

The Bethesda system for reporting thyroid cytopathology: a single-center experience over 5 years

BACKGROUND

The Bethesda System for Reporting Thyroid Cytopathology (BSRTC) was developed to refine fine-needle aspiration (FNA) cytology definitions and improve clinical management. This study evaluates the impact of the BSRTC 5 years after its adoption at a single institution.

METHODS

A total of 1,625 patients undergoing thyroidectomy in the pre-BSRTC (Group 1: July 2007-January 2009) and post-BSRTC (Group 2: February 2009-September 2013) periods were reviewed. Cytologic diagnoses in Group 1 included non-diagnostic, benign, follicular neoplasm, suspicious for malignancy and malignant. Atypia/follicular lesion of undetermined significance (AUS/FLUS) was included in Group 2. The proportions of each FNA category and malignancy rate per cytologic diagnosis were compared.

RESULTS

Fifty-four percent (187/347) of Group 1 patients had a preoperative FNA versus 61 % (777/1278) in Group 2 (p = 0.02). Group 1 FNA results included 3 % non-diagnostic, 48 % benign, 17 % follicular, 13 % suspicious for cancer, and 19 % cancer. Group 2 results included 3 % non-diagnostic, 36 % benign, 9 % follicular, 8 % suspicious for malignancy, 18 % malignant and 26 % AUS/FLUS. In Group 2, the proportions of benign, follicular and suspicious for malignancy FNAs decreased significantly (p < 0.05). In Group 2, there were more indeterminate FNA diagnoses overall (30 vs. 43 %; p < 0.001). The rate of cancer in suspicious for cancer FNA lesions increased from 44 to 65 % (p = 0.07). The AUS/FLUS malignancy rate was 15 %.

CONCLUSIONS

Since the adoption of the BSRTC at our institution, the proportion of indeterminate FNAs has increased; however, the diagnostic accuracy of the suspicious for cancer category improved. We recommend periodic review of the utilization and malignancy rates per cytologic category at each institution to help tailor clinical management.