Malignancy risk and reproducibility associated with atypia of undetermined significance on thyroid cytology

A Comprehensive Approach to the Thyroid Bethesda Category III (AUS) in the Transition Zone Between 2nd Edition and 3rd Edition of The Bethesda System for Reporting Thyroid Cytopathology: Subcategorization, Nuclear Scoring, and More

Significant interobserver variabilities exist for Bethesda category III: atypia of undetermined significance (AUS) of The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC). Thus, subcategorization of AUS including AUS "nuclear" and AUS "other" is proposed in the recent 3rd edition of TBSRTC. This study investigated the impact of the nuclear features/architectural features/nuclear score (NS) (3-tiered)/subcategories and subgroups on risk of malignancy (ROM) in thyroid fine-needle aspirations (FNA). 6940 FNAs were evaluated. 1224 (17.6%) cases diagnosed as AUS were reviewed, and 240 patients (initial FNAs of 260 nodules and 240 thyroidectomies) were included. Subcategories and subgroups were defined according to TBSRTC 2nd and 3rd editions. Histological diagnostic groups included nonneoplastic disease, benign neoplasm, low-risk neoplasm, and malignant neoplasm. Overall, ROM was 30.7%. ROM was significantly higher in FNAs with nuclear overlapping (35.5%), nuclear molding (56.9%), irregular contours (42.1%), nuclear grooves (74.1%), chromatin clearing (49.4%), and chromatin margination (57.7%), and these features were independent significant predictors for malignancy. FNAs with NS3 had significantly higher ROM (64.2%). Three-dimensional groups were significantly more frequent in malignant neoplasms (35.7%). ROM was significantly higher in AUS-nuclear subcategory (48.2%) and in AUS-nuclear and architectural subcategory (38.3%). The highest ROM was detected in AUS-nuclear1 subgroup (65.2%). ROM was significantly higher in the group including AUS-nuclear and AUS-nuclear and architectural subcategories, namely "high-risk group" than the group including other subcategories, namely "low-risk group" (42.0%vs 13.9%). In conclusion, subcategorization may not be the end point, and nuclear scoring and evaluation of architectural patterns according to strict criteria may provide data for remodeling of TBSRTC categories.

Morphometric study in thyroid tumors

Various morphonuclear studies using digital image analysis have been taken into account in order to establish the malignancy of thyroid lesions based on their size and on the chromatographic characteristics of tumor cell nuclei. Nuclear morphometry involves the measurement of nuclear parameters to obtain diagnostically important information in an objective and reproducible manner. The aim of the present study was to evaluate the detailed morphometric analysis of histopathological preparations with lesions of the thyroid gland and to investigate its role in differentiating between benign and malignant thyroid lesions. The present study included 10 benign and 26 malignant thyroid cases with different selected thyroid lesions. Using a microscope connected to a computerized video system, nuclear morphometric parameters including the nuclear area, perimeter, average intensity, red average, width and roundness, were measured and analyzed. The main parameters used in the statistical calculation were significant in distinguishing between benign and malignant thyroid lesions. The association of morphometry in cytological smears for suspected malignant follicular lesions led to increased accuracy in establishing a suspicious malignant diagnosis for follicular lesions. Nuclear morphometry provides an unbiased point of view that increases diagnosis accuracy. Computerized morphometry can positively influence diagnostic accuracy, allowing for a better correlation with clinical and imaging data.

Probability of malignancy as determined by ThyroSeq v3 genomic classifier varies according to the subtype of atypia

BACKGROUND

ThyroSeq assesses the probability of malignancy (POM) in thyroid fine-needle aspiration cytology specimens diagnosed as atypia of undetermined significance (AUS). The authors investigated whether defined AUS subcategories are associated with specific molecular alterations, the molecular-derived risk of malignancy (MDROM), and the risk of malignancy (ROM).

METHODS

Fine-needle aspiration cytology reports of AUS and corresponding results from the ThyroSeq version 3 genomic classifier results were retrieved and subcategorized as follicular cells with either cytologic atypia (FC-C), architectural atypia (FC-A), both cytologic and architectural atypia (FC-CA), or a predominance of Hurthle cells (PHC). The MDROM, ROM, and frequency of molecular alterations by subcategory were computed and analyzed, and p < .05 was considered significant.

RESULTS

The final analysis included 541 cases subdivided into 233 with FC-A, 104 with FC-C, 116 with FC-CA, and 88 with PHC. The benign call rate and positive call rate for the AUS category were 72% and 28%, respectively, which varied between AUS subcategories. The MDROM by subcategory was 15.9% FC-A, 20.5% FC-C, 33.8% FC-CA, and 14.4% PHC. Histologic follow-up was available for 155 (28%) AUS cases with a follow-up period ≥12 months. The 95% confidence intervals of the MDROMs overlapped with the ROMs. The highest MDROM and ROM were in the FC-CA subcategory. RAS mutations were present in all subcategories. BRAF V600E mutations and papillary thyroid carcinoma were most frequent in the FC-CA subcategory. Noninvasive follicular thyroid neoplasm with papillary-like nuclear features was significantly more frequent in the FC-C subcategory.

CONCLUSIONS

The current results demonstrated that AUS subcategories are associated with specific genetic alterations, the MDROM, and the ROM. Molecular results and an awareness of various cancer probabilities within AUS subcategories can allow for a more tailored management.

The Value of Second-Opinion Consultation in Nongynecologic Cytopathology

OBJECTIVES

The value of consultation in pathology has been well documented in surgical pathology, but there are few comprehensive studies of consultation cases in cytopathology. Here we report our experience with cytopathology consultation cases at a large academic center.

METHODS

A review of consultation cases at our institution was performed by searching our laboratory information system. The contributing institution's diagnosis was compared with that rendered by the reviewing cytopathologist to assess major and/or minor diagnostic discrepancies.

RESULTS

In total, 928 cases were reviewed with the following distribution: fine-needle aspiration (FNA, 79.4%), exfoliative nongynecologic cytology (18.3%), and cases with both FNA and nongynecologic cytology (2.3%). There were 379 (40.8%) true consults and 549 (59.2%) confirming consults. A total of 586 (63.1%) cases were in agreement with the outside pathologist, 78 (8.4%) cases had major discrepancies, and 264 (28.4%) cases had minor discrepancies. Major discrepancies were most common for pancreas (38.5%), lymph node (11.5%), and soft tissue sites (9.0%).

CONCLUSIONS

Of the cases, 8.4% had major diagnostic discrepancies between the original diagnosis and the consultation diagnosis, which is consistent with reported values in surgical pathology consultation studies. The findings support the importance of second-opinion consultation in cytopathology to guide patient care.

Hashimoto's Thyroiditis Does Not Influence the Malignancy Risk in Nodules of Category III in the Bethesda System

The aim of this study was to evaluate the risk of malignancy (RoM) in category III thyroid nodules of the Bethesda system in patients with and without Hashimoto thyroiditis (HT) and to analyze whether obtaining category III with a repeat FNA (rFNA) increases RoM. The study included 563 HT and 1250 non-HT patients; rFNA was performed in 349 and 575 patients, and surgical treatment in 160 and 390, respectively. There was no difference in RoM between HT and non-HT patients in the whole examined population (lower limit of RoM), nor in operated patients (upper limit of RoM), HT: 5.0−17.5%, non-HT: 4.7−15.1%. RoM in patients with AUS nodules (with nuclear atypia) was similar in both groups (HT: 21.7−40.0%, non-HT: 16.9−41.4%), as it was in patients with FLUS nodules (with architectural atypia) (HT: 3.5−13.3%, non-HT: 4.0−13.0%). In patients from both groups together, with category III diagnosed twice and AUS identified at least once, RoM was 16.7−50.0% and it was higher than that in patients with FLUS nodule diagnosed twice: 3.2−13.0% (p < 0.005). Concluding, RoM in category III nodules is not affected by the presence of HT. Subcategorization of category III nodules (FLUS vs. AUS) may provide guidance toward further follow-up or surgery in both groups.

Malignancy Rates in Thyroid Nodules Classified as Bethesda III and IV; Correlating Fine Needle Aspiration Cytology with Histopathology

Fine needle aspiration cytology (FNAC) is an integral part in the diagnostic work up of thyroid nodules. FNAC reports are based on Bethesda system for thyroid cytopathology which is one of the most commonly used systems worldwide. The main objective of the present study was to evaluate the malignancy rates in Bethesda category III and IV thyroid nodules over a six-year period. 642 thyroid FNAC were performed over a six-year period. The medical records of all these patients were reviewed using electronic patient records. Cases reported to have Bethesda category III and IV were included in the study. Data for these patients were reviewed to determine the relationship between these categories and thyroid cancer. There were 41 cases of category III of which 19 underwent surgery and the malignancy rates were found to be 26.3%. Category IV consisted of 50 cases of which 45 underwent surgery and the malignancy rates were 26.6%. The results from our study are similar to findings in larger multicentric studies which found that malignancy rates for Bethesda category III and IV were 10–30% and 25–40%, respectively.

Low reproducibility of equivocal categories of the Bethesda System for Reporting Thyroid Cytology makes the associated risk of malignancy specific to the diagnostic center

PURPOSE

Equivocal categories (III, IV, V) of the Bethesda System for Reporting Thyroid Cytology (BSRTC) are characterized by high variability of the estimated risk of malignancy. The aim of the study was to analyze the reproducibility of classification of nodules into an equivocal category and the frequency of malignancy (FoM) observed in such categories.

METHODS

Five experienced cytopathologists from three centers (A, B, C) independently performed reclassification of smears obtained from 213 thyroid nodules with equivocal routine cytology and known results of the postoperative histopathological examination.

RESULTS

The interobserver agreement among all cytopathologists was poor, with a Krippendorff's alpha coefficient equaling 0.34. The intra-center agreement was higher than the inter-center (fair vs poor). Pathologists of the center A classified smears into categories II and III significantly less often and categories IV and V more often than pathologists of centers B and C. The joint FoM of nodules classified into any of categories IV-VI (regarded as an indication for surgery) was different among centers (A: 40.0%, B: 66.7%, C: 80.6%). The FoM of category III nodules with features of nuclear atypia (AUS) in center B and C was two times higher than that of other nodules of category III (FLUS), while in center A the FoM was similar.

CONCLUSIONS

The use of published data on the risk of malignancy in nodules of particular BSRTC categories without concern for the uniqueness of the diagnostic center may lead to erroneous conclusions.

Analysis of intra-observer and inter-observer variability of pathologists for non-benign thyroid fine needle aspiration cytology according to Bethesda system categories

AIM

To examine the intra- and inter-observer variability for non-benign thyroid cytological subcategories according to the Bethesda classification system after the second review.

METHODS

Between November 2018 and May 2019, thyroid fine needle aspiration biopsies of 381 nodules were retrospectively evaluated. Among them, 74 non-benign (category III-VI) thyroid biopsies, analyzed according to the Bethesda system (pathologist 1:40 vs pathologist 2:34) by two independent pathologists, were reassessed by the same pathologists and by a cytopathologist. In this observer-blinded study, weighted Cohen's kappa was used to assess the intra-observer agreement, and Krippendorff's alpha was used to assess the inter-observer agreement.

RESULTS

At the first and second evaluations of pathologists 1 and 2, the percentage agreement was 62.5% for pathologist 1 and 58.8% for pathologist 2. The intra-observer agreement was substantial (κ = 0.705) for pathologist 1, and moderate (κ = 0.447) for pathologist 2. In the second evaluation of pathologist 1 and 2, which was compared with the cytopathologist, the agreement percentage of pathologist 1 with the cytopathologist was 50.0%, and that of pathologist 2 was 56.8%. The inter-observer agreement was below the lowest acceptable limit for an overall agreement (α = 0.634) among the three raters. The inter-observer agreement was only acceptable between the cytopathologist and the second pathologist, while it was low between the other raters. In the evaluation of the non-benign nodules, the mean category score of the cytopathologist was 3.22 and lower than both pathologists (3.73 and 3.58, respectively).

CONCLUSIONS

The intra-observer agreement of pathologists was moderate-to-substantial in the evaluation of non-benign thyroid biopsies according to the Bethesda reporting system. However, the inter-observer agreement was below the lowest acceptable limit when the cytopathologist was taken as a reference.

Is Subdivision of Atypia of Undetermined Significance AUS/Follicular Lesion of Undetermined Significance Cases According to Detailed Nuclear Features Vital for Assessing the Risk of Malignancy?

Background:

It has been known that the “atypia of undetermined significance (AUS)/follicular lesion of undetermined significance (FLUS)” category is the most problematic category in Bethesda system due to its highly heterogeneous morphological features. Recently, it has been reported that aspirates including nuclear atypia in the AUS/FLUS category have a higher risk of malignancy.

Aims:

This study aimed to assess each nuclear property in aspirates with cytological atypia and also to determine the relationship with the risk of malignancy.

Material and Methods:

We reviewed 980 AUS/FLUS fine-needle aspirations (FNAs) performed between '2012 and 2019' at a single institution. We classified these aspirates into four groups: AUS-N (nuclear atypia), AUS-A (architectural atypia), AUS-H (Hurthle cell change), and AUS-O (other). Nuclear features were detailed sub-classified; size and shape (enlargement, elongation, and overlapping), membrane irregularities (irregular contours, grooves, pseudoinclusion), and chromatin characteristics (pale chromatin). The estimated risk of malignancy (ROM) was calculated for each subgroup.

Results:

Of 980 AUS/FLUS cases, follow-up histological outcome data were available for 209 cases. Among these cases, the estimated ROM was 27.8%. The ROM were 26.4%, 15.4%, and 22.5% for AUS-N, A, and H, respectively. The most common nuclear findings associated with ROM were nuclear groove (67.9%); irregular contours (76.9%) suspected pseudoinclusion (100%) and overlapping (56%) (P < 0,001). But nuclear findings such as nuclear enlargement, mild pleomorphism, or pale chromatin have a similar ROM as architectural atypia.

Conclusion:

Although it is known that the presence of cytological atypia in an AUS/FLUS nodule increases the estimated risk of malignancy, all nuclear properties are not equally effective in predicting malignancy risk. Emphasizing nuclear atypia details in reports of AUS case may be a more sensitive way to identify nodules with a high risk of malignancy.

Usability of EU-TIRADS in the Diagnostics of Hürthle Cell Thyroid Nodules with Equivocal Cytology

The aim of this study was to compare the diagnostic effectiveness of EU-TIRADS in two groups of nodules with equivocal cytology (categories III-V of Bethesda system), with and without Hürthle cells (HC and non-HC). The study included 162 HC and 378 non-HC nodules with determined histopathological diagnosis (17.9% and 15.6% cancers). In both groups calculated and expected risk of malignancy (RoM) for high, intermediate and benign risk categories of EU-TIRADS were concordant. RoM for low risk category was higher than expected in both groups, but especially in HC (HC: 13.9%, non-HC: 7.0%, expected: 2-4%). The majority of cancers in HC of that category were follicular thyroid carcinomas (FTC) and Hürthle cell thyroid carcinoma (HTC) (60.0% vs. non-HC: 16.7%). The diagnostic efficacy of EU-TIRADS was lower in HC (the area under the receiver operating characteristics curve (AUC): 0.621, sensitivity (SEN): 44.8%, specificity (SPC): 78.9% for high risk threshold) than in non-HC (AUC: 0.711, SEN: 61.0%, SPC: 77.7%). AUC was the highest for category V (AUC > 0.8, both groups) and the lowest for category IV (inefficient, both group). If intermediate risk category was interpreted as an indication for surgery, 25% of cancers from category III and 21.4% from category IV would not be treated in the HC group (0.0% and 7.4% from non-HC group, respectively). EU-TIRADS does not aid making clinical decisions in patients with cytologically equivocal HC nodules, particularly those classified into category IV of Bethesda System for Reporting Thyroid Cytopathology (BSRTC).

What is Thy3a? A study of 336 Thy3a (AUS/FLUS) thyroid FNAs with histology compares UK RCPath with other reporting systems and shows how Thy3a subclassification can improve risk stratification and help address overuse of this category

INTRODUCTION

Thy3a (AUS/FLUS) is an indeterminate and heterogeneous category in thyroid cytology. Thy3a reporting rates vary widely, with many laboratories documenting overuse. Subclassification of Thy3a helps with risk stratification. We aimed to investigate whether subclassification can also help address Thy3a overuse. We compare the UK reporting system with other terminologies.

METHODS

An audit of thyroid fine needle aspirations (FNAs) reported at our institution between 2012 and 2017 was performed. Thy3a FNAs followed by histology were reviewed and subcategorised into four subgroups: Scanty Atypia (SA), Scanty Microfollicular (SMF), Favour Benign (FB) and Thyroiditis versus Neoplasm (TVN). Review and subclassification were blinded to histology outcomes. FNAs were correlated with histology and statistical analysis was performed.

RESULTS

Our Thy3a rate was high (24% of all thyroid FNAs). For 336 Thy3a FNAs with histology, the malignancy rates of the four subgroups were: SA 68%, SMF 20%, FB 4%, TVN 31%. There were significant associations between subgroup and malignancy risk, and between subgroup and tumour risk. On histology, SA had more malignancies than expected and FB had fewer. SA and SMF had more tumours than expected and FB had fewer. SMF and Thy3f FNAs were similar in terms of tumour and malignancy outcomes.

CONCLUSIONS

Subclassification of Thy3a FNAs into these four subgroups is recommended. This can improve risk stratification and help address overuse of Thy3a. We propose that some FB and SMF cases could be safely diverted to Thy2 and Thy3f respectively. We compare various reporting terminologies and question how indeterminate FNAs should be classified.

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.

Exploring the Inter-observer Agreement Among the Members of the Italian Consensus for the Classification and Reporting of Thyroid Cytology

Classification schemes for reporting thyroid cytology of fine needle aspiration (FNA) of thyroid nodules are largely used in clinical practice, but the level of inter-observer agreement among cytopathologists is poorly acknowledged. The present study aimed to explore the inter-observer agreement among the experienced authors of the 2014 Italian Consensus for Classification and Reporting of Thyroid Cytology (ICCRTC). A stratified randomization was performed in order to obtain a sample homogeneously distributed and representative of all ICCRTC classes. Four high-experience raters were randomly selected among the extensors of the Italian consensus. They independently reviewed 60 FNA samples blindly of the initial cytological report and clinical features. Their overall agreement was evaluated according to Fleiss' kappa. The overall inter-observer agreement was moderate (κ 0.46). Specifically, a good agreement was found when the samples were consistent for malignancy (TIR5) or were not adequate for diagnosis (TIR1) (κ 0.67 and κ 0.73, respectively). A moderate agreement was present for suspicious-for-malignant category (TIR4), and a fair agreement was recorded in the two intermediate ones (TIR3A and TIR3B) (κ 0.36 and κ 0.35, respectively). For clinical purposes, the agreement was good (κ 0.74) in differentiating cases with surgical indication (TIR4/TIR5) from those in which surgery is not essential or requires limited extension (TIR3B/TIR3A/TIR2). In conclusion, the present study confirms the reliability of ICCRTC. These data represent a reference for cytopathologists using this system and are useful for the practice of clinicians and surgeons.

High risk of malignancy in cases with atypia of undetermined significance on fine needle aspiration of thyroid nodules even after exclusion of NIFTP

BACKGROUND

Fine needle aspiration cytopathology (FNAC) is the most reliable tool for evaluating thyroid nodules. However, diagnosing Bethesda category III, atypia/follicular lesion of undetermined significance (AUS/FLUS), is a major limitation. The aim of this study was to evaluate the risk of malignancy (RoM) in AUS/FLUS nodules. A systematic review was also carried out analyzing the largest series.

METHODS

Totally 1750 cases (9%) diagnosed with AUS/FLUS were evaluated retrospectively out of 19 392 cases within last 13 years. All patients undergoing surgery for AUS/FLUS were included into the study. Histopathology results were correlated; the impact of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) diagnosis on RoM is evaluated.

RESULTS

Of the 280 patients (16%) undergoing surgery, neoplasia were detected in 177 (RoN:63.2%) and malignancy in 119 (RoM:42.5%) of these neoplasia. Follicular variant of papillary thyroid carcinoma (FVPTC) was the commonest malignancy (55.5%). Additional 58 (20.7%) nodules were neoplastic, of which 26 (9.3%) were encapsulated follicular tumors with unknown malignancy potential (FT-UMP) and 32 (11.4%) were follicular adenomas. The remaining 103 patients (36.8%) had non-neoplastic nodules. After reevaluation of the encapsulated FVPTC cases, 20 of them were NIFTP and RoM dropped to 35.4% with a relative decrease of 16.7% and an absolute decrease of 7.1%.

CONCLUSION

In our series, 42.5% of nodules with AUS/FLUS were malignant; 63.2% of them were neoplastic. The RoM and RoN for AUS/FLUS nodules are still much higher than the revised expected RoM of international guidelines even after NIFTP cases excluded. Therefore, current recommendations should be reevaluated periodically in view of detailed clinicopathologic studies.

Malignancy rates for Bethesda III and IV thyroid nodules: a retrospective study of the correlation between fine-needle aspiration cytology and histopathology

BACKGROUND

Fine-needle aspiration cytology (FNAC) has become a well-established modality in the diagnosis, staging and follow-up of thyroid nodules. FNAC outcomes are routinely classified using the Bethesda System for Reporting Thyroid Cytopathology (BSRTC), facilitating appropriate clinical management. Bethesda categories III and IV encompass varying risks of malignancy. This retrospective study established a possible association between these cytological categories and malignancy rates in patients treated at a single institution.

METHODS

Over a 6-year period, 11,627 FNAC procedures were performed on thyroid nodules. Of these, 814 (59.63%) patients were submitted to thyroidectomy. The nodules of 108 patients were classified as Bethesda category III and 47 patients as Bethesda category IV. Patient data were reviewed to establish a correlation between the FNAC results and the final histopathological analyses.

RESULTS

The rates of malignancy among patients who underwent surgery were 25% for category III and 27.6% for category IV, with no significant differences between categories (p = 0.67). The pathological parameters of malignant nodules, namely tumour type, size, encapsulation, invasion into the thyroid capsule, extrathyroidal extension and lymphovascular invasion did not significantly differ between the groups (p > 0.05).

CONCLUSIONS

This paper provides a more precise correlation of malignancy rates with thyroid nodules classified as Bethesda categories III and IV, as our findings are comparable to the literature, giving malignancy rates ranging from 10 to 30% for category III and 25-40% for category IV. Use of the BSRTC is heterogeneous across institutions, and there is some degree of subjectivity in the distinction between categories III and IV; therefore, it is crucial to estimate the rates of malignancy at each institution. Molecular assays are of increasing importance in determining the need for surgical intervention for thyroid lesions. Gene expression assays using FNAC material may demonstrate a high predictive value for cytologically indeterminate thyroid nodules diagnosed as Bethesda classes III and IV.

Thyroid nodules with Hürthle cells: the malignancy risk in relation to the FNA outcome category

PURPOSE

The aim was to find whether the presence of Hürthle cells (HC) in a smear influences the categorization of FNA results or the risk of malignancy (RoM) of particular categories of cytological diagnosis.

METHODS

25,220 FNA performed in a single center in years 2005-2017 were analyzed. Almost all the examined patients were exposed to moderate iodine deficiency for most of their lives. The distribution of FNA outcome categories was compared between two groups: with or without HC (HC and non-HC). The RoM was evaluated on the basis of postoperative histopathological examination (3082 patients).

RESULTS

HC were found in 7.5% of diagnostic FNA. HC nodules were classified into categories II (78.2% vs. 91.9%, p < 0.0000) and VI (0.4% vs. 1.2%, p = 0.0017) less often than non-HC nodules, but more frequently to categories III (14.4% vs. 5.8%, p < 0.0000), IV (11.2% vs. 0.9%, p < 0.0000) and V (1.5% vs. 0.8%, p = 0.0013). There were no significant differences in RoM between HC and non-HC nodules. The RoM in HC and non-HC nodules of particular categories of the Bethesda system was as follows: II: 1.8% vs. 0.8%, III: 9.7% vs. 3.8% when only the last FNA was considered and 10.8% vs. 6.4% when the category III in any performed FNA was considered; IV: 12.7% vs. 10.9%; V: 41.7% vs. 58.2%; and VI: 100% vs. 96.9%.

CONCLUSIONS

HC nodules are classified into categories of equivocal cytological outcomes more often than nodules without HC. Nevertheless, the presence of HC in a smear does not significantly affect the RoM of FNA categories.

Risk of malignancy in Thyroid "Atypia of undetermined significance/Follicular lesion of undetermined significance" and its subcategories - A 5-year experience

Context

Atypia of undetermined significance/Follicular lesion of undetermined significance [AUS/FLUS] is a heterogeneous category with a wide range of risk of malignancy [ROM] reported in the literature. The Bethesda system for reporting thyroid cytopathology [TBSRTC], 2017 has recommended subcategorization of AUS/FLUS.

Aims

To evaluate the ROM in thyroid nodules categorized as AUS/FLUS, as well as separate ROM for each of the five subcategories.

Settings and Design

Retrospective analytic study.

Methods and Materials

A retrospective audit was conducted for all thyroid fine-needle aspiration cytology (FNAC) from January 2013 to December 2017. Slides for cases with follow-up histopathology were reviewed, classified into the five recommended subcategories, and differential ROM was calculated.

Statistical Analysis Used

z test for comparison of proportions was done to evaluate the difference in ROM among different subcategories of AUS/FLUS. The P value of less than 0.05 was taken as statistically significant.

Results

Total number of thyroid FNACs reported was 1,630, of which 122 were AUS/FLUS (7.5%). Histopathology was available in 49 cases, out of which 18 were malignant (ROM = 36.7%). The risk of malignancy (ROM) for nodules with architectural and cytologic atypia was higher (43.8%) than ROM for nodules with only architectural atypia (16.7%).

Conclusions

The sub-classification of AUS/FLUS into subcategories as recommended by TBSRTC, 2017 may better stratify the malignancy risk and guide future management guidelines.

Diagnosing atypia of undetermined significance in thyroid fine needle aspiration samples using nuclear scoring

BACKGROUND

Atypia of undetermined significance (AUS) is an indeterminate category in the Bethesda system for reporting thyroid cytopathology. Cytological features described as atypia are not always observed in every case, and it is difficult to determine how the small population of cells with enlarged nuclei, a few grooves, and rare elongated nuclei should be classified. Therefore, there is inter-intra observer variability considering these cell types, even though the cytological criteria are well defined. Therefore, this study aimed to establish a nuclear scoring system to help in the differential diagnosis of AUS.

METHODS

Fine needle aspiration (FNA) samples that showed AUS and had surgical follow-up were included in this study. The aspirate was scored for the presence of intanuclear cytoplasmic inclusions, nuclear grooves, overlapping, enlargement, and elongation individually. The total nuclear score for each case was calculated. Statistical analysis of the association between each nuclear feature and the presence of papillary thyroid cancer (PTC) in the surgical specimens was performed. Cut-off points from the total score of these nuclear features were also calculated.

RESULTS

Nuclear grooves and overlapping were more common in malignant cases (p < 0.001 and p = 0.048, respectively). A cut-off point of ≥5.5 for the total score was sensitive and specific for defining malignancy.

CONCLUSION

The risk of PTC was higher in nodules with more prominent nuclear overlapping or nuclear groove in their FNA samples. In order to achieve a more confident AUS diagnosis, our scoring system can be helpful for thyroid FNA samples.

Patients with III and IV category of the Bethesda System under levothyroxine non-suppressive therapy have a lower rate of thyroid malignancy

Thyroid nodules (TNs) assigned to the Bethesda System categories III and IV include numerous clinical characteristics, which increase or decrease the risk of malignancy. However, there are very few data regarding the influence of TSH non-suppressive thyroid hormone therapy (NSTHT) on the risk of malignancy in patients in the aforementioned categories. We assessed the number of patients with thyroid nodules assigned to categories III and IV who take TSH NSTHT and if thyroid hormone therapy is associated with a rate of malignancy. We retrospectively analyzed the medical records of 4,716 individuals and selected 532 (11.28%) patients with Bethesda System category III and IV thyroid nodules. All participants underwent surgery, and histopathological verification was obtained in all cases. In all, 33.1% of individuals with category III and IV thyroid nodules took TSH NSTHT. In patients with category III nodules, application of NSTHT was associated with a lower rate of thyroid cancer (TC), though this observation was not significant (OR = 0.55, p = 0.381). In patients with category IV nodules, we demonstrated a significantly lower rate of TC when NSTHT was applied (OR = 0.44, p = 0.005). In conclusion, the prevalence of patients with Bethesda System category III and IV thyroid nodules who take NSTHT is high. TSH NSTHT significantly decreases a rate of malignancy in category IV, but not category III patients.

The Malignancy Risk Assessment of Cytologically Indeterminate Thyroid Nodules Improves Markedly by Using a Predictive Model

OBJECTIVES

The majority of thyroid nodules are discovered incidentally, and the management may be a challenge if the fine needle aspiration specimen yields indeterminate findings. Our aim was to develop an individualized risk prediction model to provide an accurate estimate of cancer risk in patients with cytologically indeterminate thyroid nodules.

MATERIALS AND METHODS

Clinical records, ultrasound images, and cytopathology reports of patients who underwent thyroidectomy were retrospectively reviewed. Logistic regression analysis was used to identify the predictive ability of each variable for malignancy, and a nomogram was built by integrating patients' age, multiplicity of nodules, cytology results, and suspicious ultrasound features, such as microcalcifications and irregular margins.

RESULTS

For the 233 indeterminate nodules according to the Bethesda System for Reporting Thyroid Cytopathology, the malignancy rates of the subgroups "atypia of undetermined significance," "suspicious follicular neoplasia," and "suspicious for malignancy" were 44.3, 47.7, and 88.0%, respectively. It was found that the Bethesda category "suspicious for malignancy," microcalcifications, and irregular margins were independent risk factors for malignancy. The area under the receiver operating characteristics curve was 0.784, which suggested that the presented nomogram had considerable discriminative performance.

CONCLUSIONS

The nomogram developed in our study accurately predicts the malignancy risk of thyroid nodules with indeterminate cytology by using clinical, cytological, and ultrasonographic features.

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.

Paris Interobserver Reproducibility Study (PIRST)

OBJECTIVES

In concert with the 2015 publication of The Paris System for Urinary Cytopathology (TPS), a Web-based interobserver study, co-sponsored by the American Society of Cytopathology (ASC) and International Academy of Cytology (IAC), was performed to determine diagnostic agreement among volunteer participants and with the TPS author consensus.

MATERIAL AND METHODS

Participants at various levels of training and certification were recruited through national and international cytopathology professional societies. Although the survey was open to all comers, potential participants were screened by two basic cytopathology questions. Information was collected on the level of training, practice patterns, and experience. Study participants evaluated 85 images (previously unpublished) chosen from the TPS atlas. These images spanned all diagnostic categories.

RESULTS

Of the 1993 attempts to access the survey, 1313 participants correctly answered the qualifying questions and were included in the survey. Respondents were concentrated in the United States, although many participants came from other countries. The majority of respondents were board-certified in anatomic pathology with cytopathology certification. A smaller number were cytotechnologists. Board-certified cytopathologists and specialist cytotechnologists outperformed other certifications. Practice type (academics versus non-academic), and country (US versus international) were not major factors in concordance. Diagnostic categories with the best agreement were Negative for High-Grade Urothelial Carcinoma (NHGUC; 71%), Low-Grade Urothelial Neoplasm (LGUN; 62%), and High-Grade Urothelial Carcinoma (HGUC; 57%). Indeterminate categories showed low concordance.

CONCLUSIONS

The NHGUC, LGUN, and HGUC were most correlated with diagnostic agreement among observers. This study can serve as a baseline for future comparisons.

Predictive Factors of Malignancy in Cytology of Indeterminate Follicular and Hürthle Cell Neoplasms of the Thyroid Gland

The objective of the current study was to determine the risk of malignancy in patients with thyroid nodules with cytology of indeterminate follicular and indeterminate Hürthle cell neoplasm (HN). The cytologic diagnosis of follicular neoplasm (FN) or HN remains a diagnostic challenge. Often, surgery is recommended for such lesions. A retrospective analysis was performed on 80 patients who underwent thyroid surgery following a diagnosis of indeterminate FN and indeterminate HN in thyroid fine-needle aspiration biopsy. Sex; age; family history of thyroid cancer and radiation exposure; coexisting thyroid conditions, such as solitary nodule; multinodularity; cytologic diagnosis; sonographic features; type of surgical treatment; and histopathologic results were recorded. Of the 80 patients, 52 (65%) had FN on fine-needle aspiration biopsy cytology and 28 (35%) had HN. A total of 23 patients (28.7%) had primary thyroid cancers on surgical pathology, and 57 (71.3%) had benign diagnoses. Univariate analysis showed no differences between the benign and malignant groups by sex, nodule size, family history of thyroid cancer, history of radiation exposure, presence of solitary nodule or multinodularity in the nodular features. In multivariate binary logistic regression analysis, the factors that were statistically significant predictors of malignancy were microcalcification [odds ratio (OR), 10.9; 95% confidence interval (CI), 2.18–54.7; P = 0.004], being older than 45 years (OR, 4.2; 95% CI, 1.25–14.63; P = 0.02]. The independent predictors of malignancy in FN and HN are micorcalcification and being older than 45 years, the use of which may predict the risk of thyroid cancer.

Cancer Risk Associated with Nuclear Atypia in Cytologically Indeterminate Thyroid Nodules: A Systematic Review and Meta-Analysis

BACKGROUND

Indeterminate categories of thyroid cytopathology (categories B-III and B-IV of the Bethesda system) are integrated by a heterogeneous spectrum of cytological scenarios that are generally clustered for analysis and management recommendations. It has been suggested that aspirates exhibiting nuclear atypia have a higher risk of malignancy. This study aimed to assess whether cytologically indeterminate thyroid nodules with nuclear atypia have a significantly higher cancer risk than those without nuclear atypia.

METHODS

On June 30, 2016, PubMed and EMBASE were searched for articles in English or Spanish using a search strategy developed by an endocrinologist and a librarian. Case reports were excluded, and no date limits were used. The references of all included studies were also screened for relevant missing studies. Studies were included if the prevalences of malignancy of cytologically indeterminate thyroid nodules with histological confirmation with and without nuclear atypia were reported. Studies were excluded if they had: (i) nodules suspicious for malignancy; (ii) nodules with non-indeterminate (B-III or B-IV) cytology on repeated biopsy, if performed; (iii) nodules not consecutively evaluated; or (iv) cohorts overlapping with another larger series. Two investigators independently assessed the eligibility and risk of bias of the studies. PRISMA and MOOSE guidelines were followed. Summary data were extracted from published reports by one investigator and independently reviewed by another. Data were pooled using a random-effects model. Heterogeneity was explored using subgroup analysis and mixed-effect model meta-regression. The odds ratio for malignancy of cytologically indeterminate thyroid nodules with nuclear atypia over cytologically indeterminate thyroid nodules without nuclear atypia was calculated.

RESULTS

Of 2571 retrieved studies, 20 were eligible. The meta-analysis was conducted on summary data of 3532 cytologically indeterminate thyroid nodules: 1162 with and 2370 without nuclear atypia. The odds ratio for malignancy in cytologically indeterminate thyroid nodules with nuclear atypia was 3.63 [confidence interval 3.06-4.35]. There was no evidence of publication bias, and heterogeneity was insignificant (I² < 0.01%, p = 0.40).

CONCLUSIONS

Nuclear atypia is a significant indicator of malignancy in cytologically indeterminate thyroid nodules and needs to be standardized and implemented into clinical practice.

Kulcsar M, Roberto Cernea C. Malignancy Rates in Thyroid Nodules Classified as Bethesda Categories III and IV: Retrospective Data from a Tertiary Center

BACKGROUND

Thyroid fine needle aspiration (FNA) has a well-established role in the diagnosis of thyroid nodules, and the "Bethesda system for reporting thyroid cytopathology" is used to interpret FNA results. Bethesda categories III and IV encompass varying risks of malignancy. In addition, there is some debate in the literature about how to select among many acceptable treatment approaches.

OBJECTIVES

To establish an association between these 2 cytological categories and malignancy rates in patients treated in a referral tertiary cancer center, where surgical treatment is recommended for all these patients.

METHODS

A total of 615 thyroid nodules (582 patients) were included in this retrospective study. There were 478 nodules that were classified as Bethesda category III and 137 nodules as Bethesda category IV. Electronic records were reviewed to establish a correlation between the FNA cytological results and the final histopathological analyses. Incidentally detected carcinomas were considered separately.

RESULTS

Among the bethesda category III group, 75 malignant nodules (15.7%) were coincident with the target nodule (74 patients, 16.2%). Incidental carcinomas were found in 13.8% of these patients. The remaining 403 (84.3%) target nodules were benign. Among the bethesda category IV nodules, 23 malignant nodules (16.8%) were coincident with the target nodule. Incidental carcinomas were found in 25 patients (19.7%). The other 114 target nodules were benign. A total of 46 patients (52.3%) had carcinomas in the thyroid lobe contralateral to the one containing the target nodule, and 40 patients (45.5%) had carcinomas exclusively in the contralateral lobe.

CONCLUSIONS

We observed a 16% rate of malignancy in nodules classified as bethesda category III and 17% among bethesda category IV. When incidental carcinomas were included, the rates of malignancy doubled.

Cancer Risk Stratification of Indeterminate Thyroid Nodules: A Cytological Approach

BACKGROUND

Management recommendations for thyroid nodules rely primarily on the cytological diagnosis. However, 25% of biopsies render an indeterminate cytology for which management decision is more challenging due to heterogeneity of the specimens. This study aimed to stratify the cancer risk through subcategorization of indeterminate cytology.

METHODS

The indeterminate cytological specimens (Bethesda-III or IV) of 518 thyroid nodules consecutively evaluated at our academic cancer center between October 2008 and September 2015, blinded to the histological outcome, were retrospectively reviewed. Cytological specimens were subclassified into four groups: aspirates exhibiting nuclear atypia (n = 158; 31%); architectural atypia (n = 222; 43%); oncocytic features (n = 120; 23%); or other types of atypia (n = 18; 3%). The prevalence of malignancy and odds ratio for malignancy were calculated in 323 nodules with histological confirmation.

RESULTS

The prevalence of malignancy was 26% overall (20% in Bethesda-III and 29% in Bethesda-IV; p = 0.07), and 47%, 12%, 24%, and 25% for aspirates with nuclear atypia, architectural atypia, oncocytic features, or other types of atypia, respectively. The OR of nuclear atypia over architectural atypia was 6.4 (3.4-12.2; p < 0.001), and 2.7 over oncocytic features (1.4-5.1; p = 0.01), whereas the OR of architectural atypia over oncocytic features was 0.4 (0.2-0.9; p = 0.03). Results were similar for Bethesda-III and IV aspirates when analyzed independently. Furthermore, cytological subcategories improved cytology-histology correlation, as they were associated with distinct profiles of histological diagnoses (p < 0.001).

CONCLUSIONS

Cytological subcategories can effectively stratify the risk of malignancy of thyroid nodules with indeterminate cytology and improve cytology-histology correlation.

Selection of Atypia/Follicular Lesion of Unknown Significance Patients for Surgery Versus Active Surveillance, Without Using Genetic Testing: A Single Institute Experience, Prospective Analysis, and Recommendations

BACKGROUND

Atypia/follicular lesion of unknown significance (AUS/FLUS) has variable rates of malignancy. The recommended management includes active surveillance (AS), repeated fine-needle aspiration (RFNA), diagnostic surgery, or genetic testing for malignancy. The objective of this study was to assess the management of AUS/FLUS patients in a dedicated thyroid clinic without implementing genetic testing.

METHODS

This was a single institute cohort study of all patients aged ≥18 years who underwent ultrasound-guided FNA thyroid biopsies between January 2009 and January 2013 and were followed until January 2016. The median follow-up time was 4.6 years (range 3.2-6.8 years). Forty-eight (57%) patients were referred to AS, and 36 (43%) patients were referred for diagnostic surgery. Thirty-six (75%) patients from the AS group underwent RFNA. An additional eight patients from the AS group subsequently underwent diagnostic surgery.

RESULTS

Malignancies were found in 15/44 (34%) diagnostic surgical samples, and benign cytologies were found in 61.1% of the RFNAs. Analysis of adherence to follow-up in the 36 AS patients showed an adherence rate of only 53%, with males tending to comply better than females did (31.6% vs. 5.8%, respectively; p = 0.052), especially males in their sixth decade of life.

CONCLUSIONS

Genetic tests for AUS/FLUS patients are accepted today as complementary evaluations in many well-developed health systems. Yet, when these tests are not feasible due to financial or availability issues, careful management of AUS/FLUS patients may still offer good results in the selection of patients for surgery or AS. The present results also indicate that compliance to follow-up schedules is a major consideration when selecting patients for AS.

Proposal for a novel management of indeterminate thyroid nodules on the basis of cytopathological subclasses

Indeterminate thyroid nodules include heterogeneous lesions that could benefit from a differential management. Our aim is to better define the management of the Bethesda System for Reporting Thyroid Cytopathology class III and IV nodules, by identifying cytological subcategories among Bethesda System for Reporting Thyroid Cytopathology class III associated with different clinical risk, by means of ultrasound, repeated FNAB, and BRAFV600E molecular analysis. We also evaluated the outcome of nodules not operated, over a 5-year follow-up. Out of 460 nodules (269 Bethesda System for Reporting Thyroid Cytopathology class III and 191 Bethesda System for Reporting Thyroid Cytopathology class IV), 344 were operated on surgical group and 116 followed-up conservatively (follow-up group). Bethesda System for Reporting Thyroid Cytopathology class III was divided into four subcategories on the basis of cytomorphological features (III-1, III-2, III-3, III-4). Clinical risk was defined on the basis of histological, cytological, and ultrasound data. Malignancy was higher in Bethesda System for Reporting Thyroid Cytopathology class III vs. Bethesda System for Reporting Thyroid Cytopathology class IV (34.4 vs. 26.2 %; p < 0.01). Papillary thyroid carcinoma was the most frequent cancer in each Bethesda System for Reporting Thyroid Cytopathology class (35 %). BRAFV600E diagnostic accuracy was 87 %. Repeated FNAB reclassified as benign nearly 40 % of nodules, selecting patients where surgery could be spared. Significant nodule growth occurred in 13.7 % of nodules, belonging mostly to Bethesda System for Reporting Thyroid Cytopathology class III-2 and Bethesda System for Reporting Thyroid Cytopathology class IV. Overall clinical risk was higher in Bethesda System for Reporting Thyroid Cytopathology III-1, III-4, and IV classes. We propose a differential management of Bethesda System for Reporting Thyroid Cytopathology III and IV classes and related subcategories: surgery may be indicated in Bethesda System for Reporting Thyroid Cytopathology class III-1, III-4, and IV; a conservative follow-up avoiding repeated FNAB may be appropriated in class III-3, while repeated FNAB may be useful in class III-2.

The Use of the Bethesda System for Reporting Thyroid Cytopathology in Korea: A Nationwide Multicenter Survey by the Korean Society of Endocrine Pathologists

Background

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) has standardized the reporting of thyroid cytology specimens. The objective of the current study was to evaluate the nationwide usage of TBSRTC and assess the malignancy rates in each category of TBSRTC in Korea.

Methods

Questionnaire surveys were used for data collection on the fine needle aspiration (FNA) of thyroid nodules at 74 institutes in 2012. The incidences and follow-up malignancy rates of each category diagnosed from January to December, 2011, in each institute were also collected and analyzed.

Results

Sixty out of 74 institutes answering the surveys reported the results of thyroid FNA in accordance with TBSRTC. The average malignancy rates for resected cases in 15 institutes were as follows: nondiagnostic, 45.6%; benign, 16.5%; atypical of undetermined significance, 68.8%; suspicious for follicular neoplasm (SFN), 30.2%; suspicious for malignancy, 97.5%; malignancy, 99.7%.

Conclusions

More than 80% of Korean institutes were using TBSRTC as of 2012. All malignancy rates other than the SFN and malignancy categories were higher than those reported by other countries. Therefore, the guidelines for treating patients with thyroid nodules in Korea should be revisited based on the malignancy rates reported in this study.

Comparison of risk of malignancy in a subgroup with atypia of undetermined significance/follicular lesion of undetermined significance: A meta-analysis

BACKGROUND

As heterogeneous findings are included in the atypia of undetermined significance (AUS)/follicular lesion of undetermined significance (FLUS) category, differing risks of malignancy in subgroups have been reported in several articles.

METHODS

We performed a meta-analysis of full-text publications written in English found in the Embase and PubMed databases.

RESULTS

The 4-tiered subgroup proportion meta-analysis showed that the 95% confidence interval (95% CI) of the risk of malignancy in the cellular atypia group did not overlap with the other 3 subgroups and demonstrated a significant difference. Two-tiered analysis using the cytologic and architectural atypia groups showed that cytologic atypia group had a 2.64-fold increase in the risk of malignancy compared with the architectural atypia group.

CONCLUSION

The cytologic atypia had a significantly higher risk of malignancy than the architectural atypia group, and it should be considered as a separate category.

Unusual findings in thyroid cytology and histology

INTRODUCTION

Although cytology and histopathology of thyroid lesions generally fall into common, well-defined categories, there are uncommon cases with unusual fine needle aspiration (FNA) findings or histology. Herein, we review the prevalence and characteristics of rare thyroid cytology and histopathology findings at a tertiary hospital.

METHODS

Institutional data from >31,000 patients with a thyroid pathology from 1995 to 2013 were queried. Both cytology and histology were available in 6,693 patients. After exclusion of the common cytological categories detailed by The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) and common histopathology categories, 90 patients with either an unusual FNA, histopathology, or both were identified.

RESULTS

A total of 90 cases were included (19: only unusual FNA; 25: only unusual histology; 46: both unusual cytology and histopathology). The positive predictive value of an unusual FNA for discovering an unusual lesion was 71% (95% CI: 58%-81%). The majority (66%) were females and median age was 59 years. On histopathology, 80 (88%) cases were malignant, 72 (90%) of which were initially diagnosed as malignant on FNA. Of the 10 benign lesions, 8 (80%) also had a benign FNA. Patients with unusual malignant lesions were significantly older than those with unusual benign lesions (62 vs. 44 years; P: 0.004).

CONCLUSION

Unusual cytopathological and histopathological findings in thyroid comprise a varied group of tumors that are individually rare but collectively common. A preoperative FNA with an unusual cytopathology is likely to lead to an unusual histopathological diagnosis; however, its diagnostic accuracy in differentiating benign from malignant is lower than the accuracy of cytopathology of conventional TBSRTC. Diagn. Cytopathol. 2017;45:185-190. © 2016 Wiley Periodicals, Inc.

RAS Mutations, and RET/PTC and PAX8/PPAR-gamma Chromosomal Rearrangements Are Also Prevalent in Benign Thyroid Lesions: Implications Thereof and A Systematic Review

BACKGROUND

Molecular markers associated with thyroid malignancy are increasingly being used as differential diagnostic tools for thyroid nodules. However, little has been reported recently regarding the prevalence of these markers in benign lesions. The literature was systematically reviewed to examine studies that reported on the prevalence of these markers in benign thyroid lesions.

METHODS

Appropriate studies published between January 1, 2000, and April 30, 2015, and cataloged in PubMed, Embase, Cochrane, Scopus, and Web of Science databases were searched for by combining different keywords for "thyroid tumor" with both general and specific keywords for "molecular marker" by using "AND" as the Boolean operator. All studies meeting criteria that reported the prevalence of RAS mutations, and RET/PTC and PAX8/PPAR-gamma chromosomal rearrangements in benign thyroid lesions were included for study.

RESULTS

A total of 64 articles (including 8162 patients, of whom 42.5% had benign lesions) that met all the study criteria were systematically reviewed and abstracted. Among 35 studies examining RAS mutations, the reported prevalence of RAS mutation in benign lesions ranged from 0% to 48%. In 38 studies examining RET/PTC rearrangements, the prevalence in benign lesions ranged from 0% to 68%. PAX8/PPAR-gamma rearrangements were examined in 27 studies, with the prevalence in benign lesions ranging from 0% to 55%.

CONCLUSION

The presence of these biomarkers and the tremendous variation in reports of their prevalence in benign lesions suggests the need for caution when including these markers in diagnostic decisions. Further understanding of the importance of these markers, as well as newly discovered markers of thyroid malignancy, may be required in order to avoid overtreatment of patients with benign thyroid tumors.

The role of repeat fine needle aspiration in the management of indeterminate thyroid nodules

Background

Management decisions are not straightforward when the Ultrasound Guided Fine Needle Aspiration (USFNA) demonstrates a Bethesda score of either category III or IV, and a diagnostic hemi-thyroidectomy or a repeat USFNA (r-USFNA) could be performed. The aim of this study is to assess the effectiveness of r-USFNA in the management of indeterminate thyroid nodules by evaluating the likelihood of obtaining a definite diagnosis.

Methods

We reviewed the medical records of all patients with thyroid nodules between 2011 and 2015 at the Jewish General Hospital (Montreal, Canada). Three hundred fifty-one patients who had undergone a surgical procedure (hemi or total thyroidectomy) and a diagnosis of B3 or B4 on the primary USFNA (p-USFNA) were included in the study. Ninety-six of the included patients also had a repeat USFNA prior to the surgery. Demographic data, type of procedure, and McGill Thyroid Nodule Score (MTNS) were obtained from the medical records. Malignancy rates were calculated based on the final surgical histopathology report.

Results

Upon r-USFNA, an average 76 % of patients did not change Bethesda categories, 7.4 % downgraded to a benign category. The results showed that, on an average 17.3 % of patients with p-USFNA of B3 and 20 % of patients with p-USFNA of B4, upgraded to a malignant or suspicious for malignancy category, thus changing the clinical management to total thyroidectomy. Our data demonstrates that r-USFNA facilitates choosing the correct surgery of total thyroidectomy in about 20 % of nodules that have upgraded from B3/B4 to a more definite malignant category.

Conclusions

r-USFNA in patients with indeterminate diagnoses (B3 or B4) increases categorization into more definite categories. Approximately 20 % of patients are found to have malignant thyroid nodules and suspicious for malignancy thyroid nodules upon repeating the biopsy, hence a diagnostic hemi-thyroidectomy was avoided and a more definitive surgery could be performed. Furthermore, repeat USFNA results in a fewer number of hemi-thyroidectomy and completion thyroidectomy procedures.

Current status and diagnostic values of the Bethesda system for reporting thyroid cytopathology in a papillary thyroid carcinoma-prevalent area

BACKGROUND

Most studies validating the Bethesda system for reporting thyroid cytopathology (TBSRTC) have been conducted in Western countries. We explored the current status of TBSRTC in an area where most thyroid malignancies are papillary carcinomas.

METHODS

Fine-needle aspirations (FNAs) of thyroid nodules performed in 2013 were retrospectively analyzed and the results were compared to final pathology on resection.

RESULTS

Of 1947 FNAs, 1925 (98.9%) were reported using TBSRTC. Among 381 resected lesions, 27.3% of nondiagnostic, 19.6% of benign, 56.0% of atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS), 33.3% of follicular neoplasm/suspicious for a follicular neoplasm (FN/SFN), 97.7% of suspicious for malignancy, and 100.0% of malignant lesions were malignant on pathology. The sensitivity and specificity of FNA using TBSRTC were 96.7% and 84.1%, respectively.

CONCLUSION

TBSRTC works well in an area in which papillary thyroid cancer is prevalent; however, it may underestimate malignancy rates in AUS/FLUS, benign, and nondiagnostic categories. © 2016 Wiley Periodicals, Inc. Head Neck 39: 269-274, 2017.

Correlation Between Histological Diagnosis and Mutational Panel Testing of Thyroid Nodules: A Two-Year Institutional Experience

BACKGROUND

Indeterminate thyroid fine-needle aspiration (FNA) cytology, including atypia of undetermined significance (AUS/FLUS) and suspicious for follicular neoplasm (SFN), continues to generate uncertainty about the presence of malignancy, resulting in repeated follow-up, repeat FNA, or diagnostic surgery. Mutational panel testing may improve the malignancy risk prediction in indeterminate nodules, but the general application of such testing has not been investigated extensively.

METHODS

A retrospective review was performed of all patients undergoing thyroidectomy at a tertiary care facility over a two-year period. Mutational panel test results, when present, were analyzed relative to FNA cytologic result and surgical histopathologic diagnosis. Malignancy rates, sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV) and positive and negative likelihood ratios (LR) were calculated.

RESULTS

A total of 261 operated thyroid nodules had the following initial FNA cytology results: 2% non-diagnostic, 23% benign, 28% AUS/FLUS, 11% SFN, 9% suspicious for malignancy (SUSP), and 27% malignant. The histopathologic malignancy rate was 48%, subcategorized by cytology into benign 7%, AUS/FLUS 30%, SFN 38%, and SUSP 83%. Mutations were more frequent in indeterminate nodules that were histologically malignant versus benign (p < 0.0001) or versus adenoma (p = 0.001). Mutational analysis in 44 AUS/FLUS nodules resulted in a malignancy detection sensitivity of 85%, a specificity of 65%, a PPV of 50%, a NPV of 91%, and a positive LR of 2.4. In 12 SFN nodules analyzed with ThyroSeq(®) testing, sensitivity was 100%, specificity 57%, PPV 63%, NPV 100%, and LR 2.3. Performance of the seven-gene mutational panel was not significantly different from the ThyroSeq(®) panel in the AUS/FLUS group. The malignancy yield, comparing the mutation positive AUS/FLUS group with the untested AUS/FLUS surgical cohort, did not reach statistical significance (p = 0.17).

CONCLUSIONS

In a surgical cohort, a similar NPV but a lower PPV was found with the use of mutational panel testing compared to the published literature. Following the identification of a mutation, the prevalence of malignancy in the AUS/FLUS or SFN category was increased by nearly 15% to 45% and 53%, respectively. Further study is needed to confirm these results and to analyze clinical outcome subcategories relative to the utility of mutational testing.

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.

Morphometric Analysis of Thyroid Follicular Cells with Atypia of Undetermined Significance

BACKGROUND

Atypia of undetermined significance (AUS) is a category that encompasses a heterogeneous group of thyroid aspiration cytology. It has been reclassified into two subgroups based on the cytomorphologic features: AUS with cytologic atypia and AUS with architectural atypia. The nuclear characteristics of AUS with cytologic atypia need to be clarified by comparing to those observed in Hashimoto thyroiditis and benign follicular lesions.

METHODS

We selected 84 cases of AUS with histologic follow-up, 24 cases of Hashimoto thyroiditis, and 26 cases of benign follicular lesions. We also subcategorized the AUS group according to the follow-up biopsy results into a papillary carcinoma group and a nodular hyperplasia group. The differences in morphometric parameters, including the nuclear areas and perimeters, were compared between these groups.

RESULTS

The AUS group had significantly smaller nuclear areas than the Hashimoto thyroiditis group, but the nuclear perimeters were not statistically different. The AUS group also had significantly smaller nuclear areas than the benign follicular lesion group; however, the AUS group had significantly longer nuclear perimeters. The nuclear areas in the papillary carcinoma group were significantly smaller than those in the nodular hyperplasia group; however, the nuclear perimeters were not statistically different.

CONCLUSIONS

We found the AUS group to be a heterogeneous entity, including histologic follow-up diagnoses of papillary carcinoma and nodular hyperplasia. The AUS group showed significantly greater nuclear irregularities than the other two groups. Utilizing these features, nuclear morphometry could lead to improvements in the accuracy of the subjective diagnoses made with thyroid aspiration cytology.

Institutional prevalence of malignancy of indeterminate thyroid cytology is necessary but insufficient to accurately interpret molecular marker tests

OBJECTIVE

Several molecular marker tests are available to refine the diagnosis of thyroid nodules. Knowing the true prevalence of malignancy (PoM) within each cytological category is considered necessary to select the most appropriate test and to interpret results accurately. We describe our institutional PoM among cytological categories and report our experience with molecular markers.

DESIGN

Single-center retrospective study.

METHODS

We calculated the institutional PoM for each category of the Bethesda system (Bethesda) on all thyroid nodules with cytological evaluation from October 2008 to May 2014. We estimated the predictive values for Afirma, miRInform, and ThyroSeq v2, based on published sensitivity and specificity. Finally, we assessed our own experience with miRInform.

RESULTS

The PoMs for Bethesda III and IV categories were 21 and 28%, respectively. ThyroSeq v2 achieves the highest theoretical negative and positive predictive values (NPV and PPV) in Bethesda III (98 and 75%) and Bethesda IV categories (96 and 83%). At our institution, miRInform detected a mutation in 16% of 109 indeterminate nodules tested, all in Bethesda IV specimens. Histology was available in 56 (51%) nodules. The observed sensitivity and specificity in Bethesda IV specimens were 63 and 86%, yielding an NPV and a PPV of 75 and 77%, respectively.

CONCLUSIONS

For our current Bethesda III and IV PoM, the actual performance of miRInform was worse than expected. Theoretically ThyroSeq v2 should have the best performance, but it could be affected in the same way as miRInform, given the similarities between the tests. Assessing the institutional performance of each test is necessary along with PoM individualization.

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.

Examining the Bethesda criteria risk stratification of thyroid nodules

BACKGROUND

The Bethesda criteria are proposed for appropriate stratification of malignancy risk in thyroid nodules, but controversy exists regarding their accuracy and reliability in decision making. Additionally, previous studies have suggested higher rates of both malignancy and false negative fine needle aspiration biopsy (FNA) associated with increasing nodule size. This study aims to determine the accuracy of ultrasound (US)-guided FNA using the current Bethesda criteria in surgical practice. We also aimed to investigate the relationship between nodule size and malignancy.

METHODS

A retrospective analysis of US-guided FNAs by a single surgeon during a 4.5 year period. FNA results using Bethesda criteria were compared to final surgical pathology.

RESULTS

611 patients with thyroid nodules underwent US-guided FNA. FNA results in 375 subsequently excised thyroid nodules were recorded according to the Bethesda criteria: 192 (51%) benign, 65 (17%) atypia of unknown significance/follicular lesion of undetermined significance (AUS/FLUS), 42 (11%), suspicious for follicular neoplasm (SFN), 17 (5%) suspicious for malignancy (SM), 28 (8%) malignancy, and 31 (8%) non-diagnostic. Malignancy was confirmed by surgical pathology in 15%, 34%, 50%, 88%, 100%, and 39% of the above groups respectively. Sensitivity, specificity, and false-negative rate were 61%, 99%, and 15% respectively. No correlation existed between the size of nodules with indeterminate FNA results and malignancy rate (p=0.89), or size of nodules with non-diagnostic FNA and malignancy rate (p=0.50).

CONCLUSION

The current Bethesda risk stratification system underestimated malignancy rates in benign, indeterminate and non-diagnostic cytopathologic categories in our experience. There was no positive linear correlation between nodule size and malignancy rate in these cytopathologic categories.

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.