The use of The Bethesda System for Reporting Thyroid Cytopathology in a Chinese population: An analysis of 13 351 specimens

Preoperative evaluation of thyroid nodules - Diagnosis and management strategies

Thyroid cancer is the most common endocrine malignancy, with increasing incidence over the past few decades. Fine needle aspiration (FNA) biopsy is the gold standard for preoperative diagnosis of thyroid malignancies. Nevertheless, this method renders indeterminate results in up to 30% of the cases. Therefore, these patients are often referred to unnecessary surgery to establish the diagnosis. To improve the accuracy of preoperative diagnosis, several other ways, such as ultrasonography, elastography, immunohistochemical analysis, genetic testing, and core needle biopsy, have been developed and can be used either in association with or as an alternative to FNA. This review aims to evaluate all these diagnostic tools to determine the most appropriate way of managing thyroid nodules and subsequently improve the selection of cases referred to surgery.

Outcomes of the Bethesda system for reporting thyroid cytopathology in community- vs. institution-performed cytology

OBJECTIVES

Despite the important role of the community in the assessment and risk stratification of patients with thyroid nodules, evidence-based data on the Bethesda System for Reporting Thyroid Cytopathology (BSRTC) performance in community clinics is lacking. We aim to evaluate BSRTC performance of aspirations taken in community clinics compared with primary referral center.

METHODS

Patients who underwent thyroid surgery between 2013 and 2018 at our institution were divided according to the fine needle aspirations (FNA) settings: community FNA (cFNA) vs. institutional FNA (iFNA). Demographics, BSRTC results and final pathology were collected. Diagnostic values were calculated for BSRTC categories (sensitivity, specificity, positive predictive value [PPV], and negative predictive value [NPV]), and were compared between the groups.

RESULTS

A total of 268 nodules were included in the study; 77% (207) cFNA and 23% (61) iFNA. Patients in the community were younger (51.7 ± 15.1 vs. 56.6 years±14.8, p = 0.03) and with less epidemiology risk factors for thyroid cancer (1.9% vs 13.1%, p < 0.001). cFNA malignancy rate for BSRTC I-VI was 0%, 6.4%, 11.8%, 32.1%, 91.6% and 93.8% respectively. Best sensitivity was found for BSRTC III-VI in both groups (88% and 83%, cFNAs and iFNAs, respectively). Overall best performance was obtained for BSRTC V-VI for both groups (cfNA: 85%, 97%, 93%, 94% and 93%; iFNAs: 81%, 100%, 100%, 87% and 91%, for sensitivity, specificity, PPV, NPV and accuracy, respectively).

CONCLUSIONS

Community-performed FNAs demonstrate acceptable BSRTC distribution and malignancy rates, comparable with a primary referral academic hospital. This supports the universality of the BSRTC 2017 and its recommendations also in the community.

Non-Invasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features Is Not a Cytological Diagnosis, but It Influences Cytological Diagnosis Outcomes: A Systematic Review and Meta-Analysis

BACKGROUND

A low-risk thyroid tumour, non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was introduced in 2016. NIFTP criteria require a thorough histological examination to rule out capsular and lymphovascular invasion, which denies the possibility of preoperative cytological diagnosis. Nevertheless, since the adoption of the new entity, the cytology of NIFTP has been a subject of interest.

OBJECTIVES

The present systematic review and meta-analysis investigate the cytological diagnosis of NIFTP.

METHOD

An online PubMed literature search was conducted between March 1, 2020, and June 30, 2020, for all original articles considering the cytology of histologically proven NIFTP. The studies including data on fine needle aspiration specimens classified by The Bethesda System for Reporting Thyroid Cytology (TBSRTC) categories, risk of malignancy (ROMs) in the TBSRTC categories, and cytomorphological features of NIFTP were included in the meta-analysis. Non-English studies and case reports were excluded. The data were tabulated and statistical analysis was performed with Open Meta-Analyst program.

RESULTS

Fifty-eight studies with a total of 2,553 NIFTP cases were included in the study. The pooled prevalence of NIFTP cases was calculated among 25,892 surgically resected cases from 20 studies and the results show that NIFTP consisted 4.4% (95% confidence interval [CI]: 3.5-5.4%) of all cases. Most of the NIFTP cases (79.0%) belonged to the intermediate categories of TBSRTC. The pooled distribution of NIFTP cases in each TBSRTC category was 1.3% (95% CI: 0.8-1.7%) in non-diagnostic (ND), 8.9% (95% CI: 6.9-10.8%) in benign, 29.2% (95% CI: 25.0-33.4%) in atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS), 24.2% (95% CI: 19.6-28.9%) in follicular neoplasm (FN), 19.5% (95% CI: 16.1-22.9%) in suspicious for malignancy (SM), and 6.9% (95% CI: 5.2-8.7%) in malignant. Compared to pre-NIFTP era, the pooled risk differences of ROM were reduced by 2.4% in ND, 2.7% in benign, 8.2% in AUS/FLUS, 8.2% in FN, 7.3% in SM, and 1.1% in the malignant category. The cytomorphological features of NIFTP were similar to follicular variant of papillary thyroid carcinoma (FVPTC) but lesser to papillary thyroid carcinoma (PTC).

CONCLUSIONS

Based on our results, NIFTP remains a histological diagnosis. Although cytomorphological features cannot be used in differentiating NIFTP from FVPTC, they may guide in separating NIFTP from PTC. Features such as papillae, microfollicles, giant cells, psammoma bodies, and the amount of papillary-like nuclear features should be taken into account when suspicious of NIFTP. NIFTP should not have papillae or psammoma bodies, and giant cells were rarely observed.

The Incidence of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: A Meta-Analysis Assessing Worldwide Impact of the Reclassification

Background: Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) reclassification has significantly influenced the field of thyroidology. However, the extent of this impact depends upon the incidence of NIFTP in a given population. In this meta-analysis, we aimed to obtain robust information about the actual incidence of NIFTP worldwide by reviewing the published data. Methods: Comprehensive literature search was performed using electronic databases of PubMed and Web of Science over a five-year period (January 1, 2016, to January 30, 2021). The incidence of NIFTP was calculated by dividing the number of NIFTPs by the number of papillary thyroid carcinomas (PTCs). Meta-analysis of proportion and their 95% confidence interval [CI] were pooled using the random-effect model. Heterogeneity across the included studies was assessed using I² statistics. Egger's regression test and funnel plot of estimates were used to evaluate the publication bias. p-Value <0.05 was considered significant. Results: From 505 publications, we included 50 studies, all retrospective, with 100,780 PTCs and 3990 NIFTP from 92 institutions worldwide. The overall incidence of NIFTP was 6.0% [CI 4.4-8.2] among PTCs or thyroid malignancies with a high level of heterogeneity among the included studies (I² = 98.6%). NIFTP incidence was largely similar in North America and Europe (9.3% vs. 9.6%), with a significantly lower overall rate in Asia (2.1%). There was a significant decline in the reported incidence of NIFTP in non-Asian studies published after 2017 (p = 0.002). On applying our data on global thyroid cancer statistics, this reclassification would affect ∼30,881 patients annually, with a lower impact in Asia compared with North America and Europe. Conclusions: This comprehensive meta-analysis confirms that the worldwide NIFTP incidence is much lower than estimated initially. The NIFTP rates are significantly lower in Asian compared with North American and European countries. Apart from geography, NIFTP rates are significantly influenced by the nature of study, type of database used for sample collection, and the diagnostic criteria used. Introduction of NIFTP may potentially spare over 30,000 patients worldwide annually from clinical and psychological consequences of a thyroid cancer diagnosis.

False positive cases in thyroid cytopathology - the experience of a single laboratory and a systematic review

INTRODUCTION

Fine needle aspiration (FNA) is fundamental in the pre-operative assessment of thyroid nodules. However, the shining success of thyroid FNA is occasionally eclipsed by false positive (FP) cytological diagnoses. We describe our experience regarding FP cytological diagnoses and present a literature review concerning FP rates.

MATERIALS AND METHODS

We retrospectively analyzed 2031 consecutive cytology reports. FP was defined as a case with "suspicious for malignancy" or "malignant" cytology, whose surgical follow-up failed to confirm the initial diagnosis of malignancy. We used the PubMed database for the literature review using specific search terms ("thyroid", "cytology", "false positive").

RESULTS

Out of 2031 FNA reports, 93 cases with "suspicious for malignancy" or "malignant" cytology underwent surgical excision. Histopathology did not confirm malignancy in 10 cases (0.6% FP rate). Nodules with FP cytology were significantly larger (P = 0.0024) than those with with TP (true positive) cytology. A review of 25 publications shows comparable results to ours with some slight differences. The majority of studies achieve a FP rate below 3%. Most FP cytological diagnoses turn out to be non-neoplastic lesions (nodular hyperplasia, adenomatous nodule, lymphocytic thyroiditis), which combined account for 80.5% of all histological diagnoses.

CONCLUSIONS

Thyroid nodules with FP cytology were larger than nodules with TP cytology. Most studies manage to adhere to the recommended FP rates, or values close to them, with some outliers. Nevertheless, the mean FP rate values are very close to the value recommended by The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC). The FP rate value depends on how one defines true negative cases, which can be either histologically proven benign cases, via a benign clinical course, or by assuming that cytologically benign cases remain as such.

The combination of ACR-Thyroid Imaging Reporting and Data system and The Bethesda System for Reporting Thyroid Cytopathology in the evaluation of thyroid nodules-An institutional experience

BACKGROUND

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) is widely utilised by cytopathologists. The American College of Radiology (ACR) has also proposed a thyroid imaging reporting and data system (TIRADS) to classify thyroid nodules and guide their selection for fine needle aspiration (FNA). The current study aimed to analyse the usefulness of TBSRTC in thyroid cytology reporting, to examine its histological correlation with TIRADS, and to compare the management of lesions in each cytological category in our institute to the TBSRTC recommendations.

MATERIALS AND METHODS

A retrospective study was performed on all thyroid FNAs from a 2-year period at a tertiary care centre. Histological correlations of TBSRTC and ACR TIRADS were examined for cases with surgical follow-up, and the risk of malignancy in each TBSRTC category, and sensitivity and specificity of FNA and TIRADS, were calculated.

RESULTS

A total of 337 thyroid FNAs were examined, with histological follow-up in 99 cases. Risk of malignancy in categories I-VI was 9.5%, 2.3%, 0.0, 8%, 87.5% and 100.0%, respectively. The sensitivity, specificity, positive predictive value, and negative predictive value of FNA were 60.0%, 99.0%, 85.7%, and 97.5%, respectively, while those values for thyroid ultrasound were 90.3%, 72.2%, 92.9% and 65%, respectively.

CONCLUSION

The study substantiates the usefulness of TBSRTC in arriving at a more precise diagnosis. Hurthle cell lesions with atypia were the common cause of misdiagnosis. The combination of TIRADS and TBSRTC aids in better stratification of thyroid nodules and in decision making for management of lesions.

Validating the 'CUT score' risk stratification tool for indeterminate thyroid nodules using the Bethesda system for reporting thyroid cytopathology

PURPOSE

Managing intermediate thyroid nodules remains challenging. The CUT score is an Italian metanalysis-based cytologic (SIAPEC-IAP) scoring system, designed to assist clinicians. However, it was never evaluated against the Bethesda system for reporting thyroid cytopathology (BSRTC). This study aims to validate its utility for BSRTC III and IV nodules in a non-Italian population.

METHODS

We collected all BSRTC III and IV thyroid nodules with a documented final pathology between 2010 and 2020. We calculated the C + U components of the CUT score using retrospective clinical (C) data collection and reevaluation of preoperative sonography (U) examination. The cytology (T) component which originally referred to the five-tiered SIAPEC-IAP cytologic classification was replaced by the corresponding BSRTC categories. Optimal test performances were calculated using receiver operating characteristic (ROC) curve analysis. Data were analyzed twice with considering of NIFTP as benign and as malignant.

RESULTS

After exclusions, 62 nodules from 61 patients were included (50% BSRTC III, 50% BSRTC IV). Malignant nodules demonstrated a significantly higher C + U score compared with benign in both categories. The C + U cutoff value for BSRTC III was 5.25 (sensitivity and specificity of 69.23% and 66.67%, respectively, AUC = 0.72, p-value = 0.016), and 5.75 for BSRTC IV (sensitivity and specificity of 85.7% and 76.5%, respectively, AUC = 0.84, p-value < 0.001).

CONCLUSION

Our study suggests that the CUT score is applicable for both BSRTC III and IV nodules, and highlights the need for internal validations, since the cutoffs found were higher than previously reported.

Three ultrasound phenotypes of non-invasive follicular thyroid neoplasm with papillary-like nuclear features proposed for imaging-pathology analysis: single center experience

Background

The terminology "non-invasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP) was introduced to reduce overtreatment of thyroid carcinomas with indolent behavior. However, limited literature discussed the sonographic features of the entity in depth. The objective of this study is to summarize sonographic subtypes of NIFTP for precise diagnosis.

Methods

From January 2017 to June 2020, 13,531 consecutive patients underwent surgery for thyroid nodules were reviewed; 30 patients (0.22%) with 30 NIFTP were eligible for this retrospective observational study. We evaluated ultrasound features of all the lesions and distributed them into 3 major types of ultrasound appearance using pattern recognition. Systemic literature review concerning ultrasonography of NIFTP was also performed.

Results

At sonography, all the NIFTP lesions were classified into three types: 19 (63.3%) were categorized into type A-oval and solid nodule without other high-suspicion features, 7 (23.3%) into type B-partially cystic mass without high-suspicion features, 4 (13.3%) into type C-hypoechoic solid nodule with high-suspicion features including irregular margins, microcalcifications, taller-than-wide shape.

Conclusions

Three ultrasound patterns were proposed by us for ultrasound-cytopathology correlation analysis.

The diversities in thyroid cytopathology practices among Asian countries using the Bethesda system for reporting thyroid cytopathology

Background

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) has been adopted and widely used among Asian countries. This study aims to investigate the application of TBSRTC in thyroid cytology practice among Asian countries.

Methods

We searched electronic databases including PubMed and Web of Science from 2010 to 2019. Meta-analysis of proportion and their 95% confidence intervals (CIs) were calculated using the random-effect model. Meta-regression and subgroup analysis were used to search for heterogeneity origins.

Results

We included 42 Asian studies with 84.953 fine-needle aspirations. Among six categories, benign was the most commonly diagnosed category. The resection rate (RR) and risk of malignancy (ROM) were highest in malignant and SM categories, and lowest among benign nodules. Thyroid cytology practice in Asia was characterized by a low RR and high ROM in patients with indeterminate thyroid nodules. There was a significant amount of heterogeneities of TBSRTC outputs (frequency, resection rate, and malignancy risk) among Asian countries. Meta-regression showed that the sources of heterogeneity might stem from the differences in study origin and the application of molecular testing. We highlighted the usefulness of preoperative molecular testing to select patients for surgery.

Conclusions

Our study provided insight regarding thyroid cytology practice among Asian countries. Active surveillance is commonly used in Asian practice resulting in a low RR and high ROM for indeterminate nodules. There are still variations in general thyroid cytology practice in Asia. Future guidelines and consensus regarding the application of TBSRTC in thyroid cytology practice among Asian countries are required.

Atypia of undetermined significance/follicular lesion of undetermined significance: Asian vs. non-Asian practice, and the Singapore experience

The Bethesda System for Reporting Thyroid Cytopathology has paved the way for comparisons of the practice of thyroid cytology in many different regions. However, there have been comparatively few studies documenting differences between Asian and non-Asian practice. Here, we aim to compare a few key parameters between the two regions, focusing on the indeterminate category of atypia of undetermined significance (AUS)/follicular lesion of undetermined significance (FLUS). We compared its incidence, resection rates (RRs), risk of malignancy (ROM), rate of repeat fine needle aspiration (rFNA), ROMs of cytomorphologic subcategories of nuclear atypia (AUS-N) vs. architectural atypia (AUS-A), and, finally, the incidence of papillary thyroid carcinoma (PTC) vs. follicular neoplasms (FNs) in resected AUS/FLUS cases in Asian and non-Asian regions. Where possible, these metrics were compared with the Singapore experience from a tertiary referral institution. While the incidence of AUS/FLUS was similar in both regions, we found geographical differences in the RRs and ROMs, which may reflect a higher collective threshold for surgery in Asian countries. However, both cohorts showed higher ROMs in the AUS-N subcategory as compared to the AUS-A subcategory, supporting the subclassification of the AUS/FLUS based on the presence of nuclear atypia. We also observed a higher incidence of AUS-N coupled with a higher incidence of PTC in resected AUS/FLUS nodules in Asian cohorts, while AUS-A and follicular-patterned neoplasms featured more prominently in the non-Asian cohorts. These incidences may account for the starkly different molecular approaches that we noted-in Asian (chiefly Korean and Chinese) centers, BRAF mutational analysis was favored, while gene panels and gene expression classifiers were more frequently applied in non-Asian centers (chiefly in the United States of America). Overall, the data from Singapore appears more closely aligned to non-Asian trends, despite its geographical location in Southeast Asia and its predominantly Asian population. We conclude that there is significant heterogeneity in the outcomes of the AUS/FLUS categories between and within regions, which is only partially explained by regional variations, and may also reflect different regional diagnostic and management practices. This highlights the importance of understanding the local context in the interpretation of indeterminate Bethesda categories, rather than adopting a "one-size fits all" approach.

BRAFV600E mutation combined with American College of Radiology thyroid imaging report and data system significantly changes surgical resection rate and risk of malignancy in thyroid cytopathology practice

Background

Ultrasonography patterns and molecular testing may assist in stratifying the malignancy risk of indeterminate cytology diagnosis. The purpose of this study was to assess the value of fine needle aspiration (FNA) cytology in combination with American College of Radiology Thyroid Imaging Reporting and Data System (ACR TI-RADS) and BRAF^V600E mutation in differentiating high-risk thyroid nodules.

Methods

From February 2010 to February 2014, 2,643 consecutive thyroid nodules from 2,399 patients (688 men and 1,711 women; mean age, 44.3±12.5 years) who underwent preoperative FNA biopsies were enrolled. The Jiangsu Institute of Nuclear Medicine has adopted TI-RADS stratification and BRAF^V600E mutation analysis as a routine procedure to assist in evaluating FNA cytopathology since January 2016. From February 2017 to July 2018, 1,905 thyroid nodules of 1,837 patients (501 men and 1,336 women, 49.5±12.8 years) who underwent preoperative ultrasound-guided FNA biopsies with BRAF^V600E mutation analysis and ACR TI-RADS grading data available were enrolled for comparison in this study.

Results

The cancer risk in nodules with BRAF^V600E mutation was 99.7% (905/908) according to the histological findings. The risk of malignancy (ROM) was found to increase with advancing ACR TI-RADS category. High-risk ultrasound features (TI-RADS 5) did show a good performance in predicting malignancy (98.1%). The combination of TI-RADS 5 and BRAF^V600E mutation reached the best diagnostic efficiency [sensitivity 97.7%, specificity 94.8%, positive predictive value (PPV) 99.6%]. It is apparent that after the implementation of ACR TI-RADS and the BRAF^V600E mutation analysis, the resection rates (RRs) of The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) I and III categories showed significant decreases (39.1% vs. 21.6% and 36.1% vs. 16.7%, respectively). In contrast, the risks of malignancy of TBSRTC I and III categories indicated substantial increases (41.5% vs. 80.0% and 34.6% vs. 50.0%, respectively). The ROM of thyroid nodules with nondiagnostic (ND, I) category showed the most significant increase of 41.5% to 80.0%.

Conclusions

ACR TI-RADS, together with BRAF^V600E mutation and cytological diagnoses, can assist in improving the prediction of malignancy of thyroid nodules, especially in the TBSRTC I and III categories.

Core-Needle Biopsy Does Not Show Superior Diagnostic Performance to Fine-Needle Aspiration for Diagnosing Thyroid Nodules

PURPOSE

To compare the diagnostic performances of fine-needle aspiration (FNA) and core-needle biopsy (CNB) for thyroid nodules according to nodule size.

MATERIALS AND METHODS

This retrospective study included 320 thyroid nodules from 320 patients who underwent both FNA and CNB at outside clinics and proceeded with surgery in our institution between July 2012 and May 2019. According to nodule size, the diagnostic performances of FNA and CNB were calculated using various combinations of test-negatives and test-positives defined by the Bethesda categories and were compared using the generalized estimated equation and the Delong method.

RESULTS

There were 279 malignant nodules in 279 patients and 41 benign nodules in 41 patients. The diagnostic performance of FNA was mostly not different from CNB regardless of nodule size, except for negative predictive value, which was better for FNA than CNB when applying Criteria 1 and 2. When applying Criteria 3, the specificity and positive predictive value of FNA were superior to CNB regardless of size. When applying Criteria 4, diagnostic performance did not differ between FNA and CNB regardless of size. After applying Criteria 5, diagnostic performance did not differ between FNA and CNB in nodules ≥2 cm. However, in nodules ≥1 cm and all nodules, the sensitivity, accuracy, and negative predictive value of CNB were better than those of FNA.

CONCLUSION

CNB did not show superior diagnostic performance to FNA for diagnosing thyroid nodules.