Thyroid nodules with Bethesda system III cytology: can ultrasonography guide the next step?

Evaluation and management of thyroid nodules with atypia/follicular lesion of undetermined significance on fine-needle aspiration

Since the introduction of the Bethesda System for Reporting Thyroid Cytopathology in 2008, the management of thyroid nodules has become more standardized, with clearly defined algorithms based on risk of malignancy for each of the six cytologic categories. However, the management of a thyroid nodule with a fine-needle aspiration biopsy classified as Bethesda III, or atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS), remains controversial due to the cytologic heterogeneity and the variability in the reported rates of malignancy. In this review, the history and rationale for the new Bethesda III category is examined, the reported incidence and risk of malignancy from published studies is reviewed and recommendations for management of patients with a thyroid nodule and AUS/FLUS are provided. Recent advances in molecular analysis and their role in the evaluation of patients with AUS/FLUS are also discussed.

Risk factors associated with malignancy and with triage to surgery in thyroid nodules classified as Bethesda category III (AUS/FLUS)

BACKGROUND

Selection of nodules for surgery diagnosed as Bethesda category III [atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) category] is very important. We aimed at to define the predictive factors for malignancy and factors associated with triage to surgery.

METHODS

The records of all patients with nodules who underwent fine needle aspiration biopsy (FNAB) and classified by Bethesda reporting system as AUS/FLUS between 2011 and 2015 at our institution were reviewed. Univariate and multivariate analysis were performed to select independent factors associated with thyroid cancer and with triage to surgery. Using independent risk factors for malignancy predictive index categories were created.

RESULTS

Of the 485 patients who were classified as AUS/FLUS on initial FNAB, 153 underwent surgery with the associated malignancy rate of 22.8%. The malignancy rates for AUS/FLUS patients with and without repeat FNAB were 37.5% and 16.2%, respectively. Multivariate logistic regression analysis revealed that solid structure, microcalcification, hypoechogenicity, increased vascularization, and irregular margin were found to be significant and independent risk factors associated for malignancy, and solid structure, microcalcifications, increased nodule size (≥2 cm) and younger patient age (<65 years) were associated with triage to surgery.

CONCLUSIONS

Our findings showed that using predictive factors for malignancy in AUS/FLUS category as risk indices, an important proportion of patients (35%) who had nodules without any risk factors could be spared unnecessary surgery. We suggest that predictive indices should be considered for selection of the patients to triage to surgery.

Impact of Microcalcifications on Risk of Malignancy in Thyroid Nodules with Indeterminate or Benign Cytology

Objective

Adverse sonographic features such as microcalcification may predict increased likelihood of malignant cytology by fine-needle aspiration and, accordingly, increased risk of malignant histology. Our objective was to study the predictive value of microcalcifications and other sonographic features for malignancy among thyroid nodules with benign or indeterminate cytology.

Study Design

Case series with chart review.

Setting

Academic teaching hospital.

Subjects

Patients (N = 769) with 858 thyroid nodules undergoing 1142 ultrasound fine-needle aspirations; 411 cases had surgical correlation.

Methods

Sonographic features predictive of malignancy were correlated with malignancy as determined by histology. Incidental malignancies occurring outside the index nodule were discounted.

Results

Cytology was inadequate (87 cases), benign (518), indeterminate (210), and malignant (44). In 32 cases, initial benign cytology was upgraded to a higher-risk category after repeat ultrasound fine-needle aspiration. Microcalcification ( P = .001) and irregular margins ( P = .04) were significantly predictive of malignant cytology. Among surgical cases, microcalcification ( P < .001) and irregular margins ( P = .04) were significantly predictive of malignant histology; 170 patients with initial benign cytology and 161 with indeterminate cytology underwent surgery. Microcalcification was significantly associated with malignancy among cases with indeterminate cytology ( P = .04) but not among cases with benign cytology ( P = .23); however, only 13 of 33 cases with benign cytology and microcalcifications underwent surgery.

Conclusion

Presence of microcalcification increases the risk of malignancy in thyroid nodules with indeterminate cytology and may thus aid in selection of cases for surgery.

Risk of malignancy for each Bethesda class in pediatric thyroid nodules

PURPOSE

The Bethesda classification for cytology is used to classify thyroid nodules into one of six categories, and for each category there is an implied cancer risk and also recommendation for management. Despite lack of data in children, the American thyroid association promotes the use of the same management guidelines as in adults. Our aim was to study the risk of malignancy for each Bethesda class in children with thyroid nodules.

METHODOLOGY

We included all patients ≤18years of age that had underwent a thyroid fine needle aspiration (FNA) at one of two centers between January 1998 and July 2013. FNA results were reclassified according to the Bethesda criteria. Histological, repeat cytological, radiological and clinical follow-up were recorded.

RESULTS

Fifty-six patients (66 nodules) underwent FNB. Mean age was 13.6 years. Numbers of nodules reported as BI-BVI were 7, 38, 11, 4, 3 and 3, respectively. Follow-up was achieved for 55 (83%) nodules. Twelve (18%) nodules were malignant by histology and revealed papillary (n=7), follicular (n=3) or insular thyroid cancer (n=2), The proportion of nodules with malignancy for BI-BVI was: 0%, 0%, 18%, 100%, 100% and 100%.

CONCLUSION

The rate of malignancy in thyroid nodules in children seems to be higher than reported in adults. The Bethesda criteria seem to accurately identify benign nodules, but other categories have a very high rate of malignancy and BIII nodules pose a particular challenge.

Repeat Diagnoses of Bethesda Category III Thyroid Nodules: What To Do Next?

Objectives

To assess the malignancy rates of thyroid nodules repeatedly classified as Bethesda category III on fine needle aspiration (FNA), and to suggest management guidelines for these lesions.

Methods

This is a retrospective study that included 395 thyroid nodules categorized as Bethesda III undergone either surgery or ultrasound (US) follow-up. There were 67 nodules classified a second time as Bethesda category III on repeat FNA. We compared malignancy rates, clinicopathologic and ultrasonographic characteristics between direct surgery and repeat FNA groups and between the initial and repeat Bethesda category III groups, each. And in the repeat Bethesda III group, clinicopathologic and US variables were compared between benign and malignant nodules.

Results

Incidence of concurrent cancer, underlying thyroiditis and positive BRAF mutation were significantly higher in 142 nodules with direct surgery than 243 nodules with repeat FNA (p < 0.05). Of the 395 nodules with Bethesda category III cytology on initial FNA, the malignancy rate was 59.5%. In 67 nodules with repeat Bethesda III classification, however, the malignancy rate was 73.1% (p < 0.05). However, none of the variables were significantly different between the initial Bethesda category III group and the repeat Bethesda category III group (p > 0.05). In the repeat Bethesda category III group, solid consistency, irregular/microlobulated margins, nonparallel shape, and number of suspicious findings or “suspicious malignant” US assessments were associated with a high malignancy rate (p < 0.05). On multivariate logistic regression analysis, the factor associated with malignancy in the repeat Bethesda category III group was irregular/microlobulated margin (odds ratio = 15.576; 95% CI, 2.097–115.6804, p = 0.007) with a sensitivity, specificity, positive and negative predictive values, and accuracy of 81.6%, 83.3%, 93.0%, 62.5% and 82.1%, respectively.

Conclusion

Thyroid nodules with repeated Bethesda category III classification and irregular/microlobulated margins on US are at increased risk of malignancy, and operative management should be considered as opposed to repeat FNA.

Atypia of undetermined significance and follicular lesions of undetermined significance: sonographic assessment for prediction of the final diagnosis

OBJECTIVES

To determine whether radiologic assessment of thyroid nodules can potentially help guide clinical management after a cytologic diagnosis of atypia of undetermined significance or a follicular lesion of undetermined significance.

METHODS

We identified 41 patients with 41 thyroid nodules initially diagnosed as atypia or follicular lesions of undetermined significance on fine-needle aspiration that were subsequently definitively diagnosed by either surgical resection or repeated fine-needle aspiration. All sonograms of nodules were reviewed by 2 blinded board-certifiedradiologists. Lesions were assessed in 3 ways: (1) Mayo pattern classification as benign, indeterminate, or worrisome for malignancy (Ultrasound Q 2005; 21:157-165); (2) thyroid imaging reporting and data system scores (scale of 1-5) based on 2 different previously published scoring criteria (Park et al [Thyroid 2009; 19:1257-1264] and Kwak et al [Radiology 2011; 260:892-899]); and (3) binary classification as benign or malignant.

RESULTS

Of the 41 nodules, 25 had benign histologic findings, and 16 were malignant. Mayo pattern classification was 100% accurate for the benign score. Lesions with a Mayo score of indeterminate were malignant in 21% of cases (6 of 28) and benign in 79% (22 of 28). Lesions with a Mayo score of malignant were malignant in 91% of cases (10 of 11) and benign in 9% (1 of 11). Thyroid imaging reporting and data system scores had area under the receiver operating characteristic curve values of 0.827 for Park scores and 0.822 for Kwak scores. Radiologist binary classification of thyroid nodules showed 88% overall accuracy.

CONCLUSIONS

Radiologist assessment of thyroid nodules in cases of atypia of undetermined significance or follicular lesions of undetermined significance is highly predictive of the final diagnosis and can help guide management of thyroid nodules of these pathologic types.

Thyroid imaging reporting and data system score combined with Bethesda system for malignancy risk stratification in thyroid nodules with indeterminate results on cytology

CONTEXT

The thyroid imaging reporting and data system (TI-RADS) was designed to better select patients who had undergone fine-needle aspiration biopsies (FNABs) with high sensitivity and accuracy. However, the combination of TI-RADS scores and Bethesda system categories in indeterminate thyroid nodules has not been examined extensively.

OBJECTIVE

This study aimed to stratify indeterminate thyroid nodules (Bethesda categories III, IV and V) according to risk of malignancy as determined by combining TI-RADS score with Bethesda system classification.

DESIGN

Retrospective study. Histopathological, cytological and ultrasound (US) data were available for 242 cases after surgery, including 136 indeterminate nodules.

METHODS

All thyroid cytopathological slides and US reports were reviewed and classified according to Bethesda system and TI-RADS categories. The malignancy rate was determined for each Bethesda category, TI-RADS score and both methods combined of indeterminate nodules.

RESULTS

The malignancy rates were 8·7%, 51·3% and 67·5% for Bethesda categories III, IV and V, respectively. Based on histopathological comparison, the accuracy was 66·7% for TI-RADS greyscale. TI-RADS 3 and 4A scores were observed in 80% of Bethesda III cases, which led to 80% sensitivity and 90% of negative predictive value (NPV). In contrast, for nodules scored as TI-RADS 4B and 5, the combined cytological results of Bethesda IV and V resulted in a higher risk of malignancy (75% and 76·9%, respectively, P < 0·001).

CONCLUSIONS

In view of the high NPV of TI-RADS 3/4A only in Bethesda III category, a surgical approach could be considered for lesions defined as Bethesda III, IV and V when TI-RADS 4B and 5 were concomitant.

The potential diagnostic role of the number of ultrasonographic characteristics for patients with thyroid nodules evaluated as bethesda I-v

Objective: Fine-needle aspiration cytology (FNAC) is considered to be the most reliable method of examination for thyroid nodules. However, when thyroid nodules are evaluated as Bethesda I–V, the role of ultrasonography is considered to be enhanced. We investigated the association between a number of ultrasonographic (US) characteristics and the risk of thyroid malignancy, and assessed the optimal compromise on the number of US characteristics for predicting thyroid malignancy.

Methods: Seventy-three patients, whose thyroid nodules were evaluated as Bethesda I–V by FNAC prior to surgery, were treated surgically. A number of US characteristics, such as microcalcification, irregular margins, hypoechogenicity, a taller-than-wide shape, and the absence of halo sign, were assessed before surgery. The optimal compromise on the number of US characteristics was analyzed using a receiver operating characteristics (ROC) curve. The area under the ROC curve (AUC) represents the overall discriminatory ability of a test.

Results: The risk of malignancy was 11.8% in patients without any US characteristics, 44.4% in those with one characteristic, 61.5% in those with two characteristics, 75% in those with three characteristics, 90% in those with four characteristics, and 100% in those with five characteristics. The AUC was favorable (0.81599). At least two US characteristics were revealed to be the optimal compromise on the number of US characteristics based on the ROC curve.

Conclusion: We proved the role of the number of US characteristics in predicting thyroid malignancy. It was thought that a surgical approach should be considered for patients with at least two US characteristics.

Thyroid nodules with atypia or follicular lesions of undetermined significance (Bethesda Category III): importance of ultrasonography and cytological subcategory

BACKGROUND

One possible result of fine-needle aspiration (FNA) in patients with thyroid nodules is "follicular lesion of undetermined significance" (FLUS) or "atypia of undetermined significance" (AUS). The risk of malignancy is relevant information to define appropriate management, and knowledge of predictors of malignancy in these nodules is therefore important. The objective of this prospective study was to evaluate clinical, laboratory, ultrasonographic, and cytological predictors of malignancy in patients with thyroid nodules and FLUS/AUS cytology.

METHODS

The sample consisted of 150 patients with thyroid nodules and an indication for FNA whose cytology was classified as FLUS/AUS according to the Bethesda classification criteria.

RESULTS

In the second FNA, cytology was nondiagnostic in 2 (1.3%) nodules and benign in 54 (36%), FLUS/AUS cytology persisted in 73 (48.6%), and cytology was suspicious for follicular neoplasm in 11 (7.3%) and for malignancy in 10 (6.6%). The rate of malignancy was 22.6%. Clinical and laboratory data or nodule size were not predictors of malignancy. The rate of malignancy was lower in nodules initially classified as FLUS (10.8% versus 41.3% with AUS). Ultrasonography (US) was also useful for predicting malignancy, with sensitivity, specificity, and positive and negative predictive values of 79.4%, 90.5%, 71%, and 93.75%, respectively. Different malignancy rates were obtained when the two parameters, cytological subcategory and US, were combined: (i) 3.9% for nodules nonsuspicious on US and FLUS, (ii) 11.4% for nonsuspicious nodules with AUS, (iii) 46.6% for suspicious nodules with FLUS, and (iv) 87% for suspicious nodules with AUS.

CONCLUSIONS

The combination of cytological subcategory (FLUS or AUS) and US provides different risks of malignancy for nodules initially classified as Bethesda category III.

Bethesda III thyroid nodules: the role of ultrasound in clinical decision making

BACKGROUND

Assessment for thyroid nodules includes ultrasound (US) and cytology according to the Bethesda classification. There is no firm consensus regarding clinical management for nodules classified as Bethesda III. Our aim was investigate the value of US to predict malignancy in these nodules.

METHODS

Patients with Bethesda III nodules who underwent thyroid surgery from July 2011 to July 2013 were included. Inclusion criteria mandated that US were available for review by two observers blinded to each other's results and histological outcome. The nodules were scrutinized with six US criteria: hypoechoic attenuation (HA), irregular margins (IM), taller than wide, microcalcifications (MC), loss of halo, and increased central vascularity. Disagreements between observers were solved by consensus.

RESULTS

There were 141 patients (121 women) with a mean age of 55 years. Mean nodule size was 25 mm. The malignancy rate was 13 %. Interobserver ratios were moderate to very strong for all six predictors (kappa = 0.60-0.94). However, only HA, IM, and MC were predictors of malignancy by univariate analysis (all p < 0.002). Logistic regression revealed an odds ratio of malignancy versus no malignancy for HA 4.8, IM 3.3, and MC 4.0 (all p < 0.05). The positive and negative predictive value for malignancy when having one or more of these three criteria was 22 % and 98 %, respectively.

CONCLUSION

HA, IM, and MC were predictors of malignancy in Bethesda III nodules. In addition, the negative predictive value for any of these three criteria was high; a nodule that lacks all of these three criteria is thus unlikely to be malignant.

Benign Aspirates on Follow-Up FNA May Be Enough in Patients with Initial Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance

Background. Management of thyroid nodules with benign aspirates following atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) is not well established. We reviewed the risk of malignancy and the role of ultrasound (US) features among thyroid nodules with benign results following initial AUS/FLUS diagnoses. Methods. From December 2009 to February 2011, a total of 114 nodules in 114 patients diagnosed as benign on follow-up fine-needle aspiration (FNA) after AUS/FLUS results were included in our study. Eight among 114 nodules were confirmed pathologically and 106 were clinically observed by a follow-up FNA or US. Suspicious US features were defined as markedly hypoechogenicity, irregular or microlobulated margin, presence of microcalcifications, and taller than wide shape. Results. There were 110 (96.5%) benign nodules and 4 (3.5%) malignant nodules. Two (4.8%) among 42 nodules without suspicious US features and 2 (2.8%) out of 72 nodules with suspicious US features were confirmed as malignancy, but there were no significant associations between the malignancy rate and US features (P = 0.625). Conclusion. Clinical follow-up instead of surgical excision or continuous repeat FNA may be enough for benign thyroid nodules after AUS/FLUS. The role of US features might be insignificant in the management of these nodules.