Eliminating the "Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance" category from the Bethesda System for Reporting Thyroid Cytopathology

Diagnostic utility of RAS mutation testing for refining cytologically indeterminate thyroid nodules

RAS mutations are prevalent in indeterminate thyroid nodules, but their association with malignancy risk and utility for diagnosis remains unclear. We performed a systematic review and meta-analysis to establish the clinical value of RAS mutation testing for cytologically indeterminate thyroid nodules. PubMed and Embase were systematically searched for relevant studies. Thirty studies comprising 13,328 nodules met the inclusion criteria. Random effects meta-analysis synthesized pooled estimates of RAS mutation rates, risk of malignancy with RAS positivity, and histologic subtype outcomes. The pooled mutation rate was 31 % (95 % CI 19-44 %) among 5,307 indeterminate nodules. NRAS mutations predominated at 67 % compared to HRAS (24 %) and KRAS (12 %). The malignancy rate with RAS mutations was 58 % (95 %CI=48-68 %). RAS positivity increased malignancy risk 1.7-fold (RR 1.68, 95 %CI=1.21-2.34, p=0.002), with significant between-study heterogeneity (I2=89 %). Excluding one outlier study increased the relative risk to 1.75 (95 %CI=1.54-1.98) and I2 to 14 %. Funnel plot asymmetry and Egger's test (p=0.03) indicated potential publication bias. Among RAS-positive malignant nodules, 38.6 % were follicular variant papillary carcinoma, 34.1 % classical variant, and 23.2 % follicular carcinoma. No statistically significant difference in the odds of harboring RAS mutation was found between subtypes. In conclusion, RAS mutation testing demonstrates clinical utility for refining the diagnosis of cytologically indeterminate thyroid nodules. Positivity confers a 1.7-fold increased malignancy risk, supporting use for personalized decision-making regarding surgery vs. monitoring. Follicular variant papillary carcinoma constitutes the most common RAS-positive malignant histological subtype. See also the graphical abstract(Fig. 1).

Repeat Fine Needle Aspiration Cytology Refines the Selection of Thyroid Nodules for Afirma Gene Expression Classifier Testing

Background: Molecular testing (MT) refines risk stratification for thyroid nodules that are indeterminate for cancer by fine needle aspiration (FNA) cytology. Criteria for selecting nodules for MT vary and remain largely untested, raising questions about the best strategy for maximizing the usefulness of MT while minimizing the harms of overtesting. We used a unique data set to examine the effects of repeat FNA cytology-based criteria for MT on management decisions and nodule outcomes. Methods: This was a study of adults (age 25-90 years; 281 women and 72 men) with cytologically indeterminate (Bethesda III/IV) thyroid nodules who underwent repeat FNA biopsy and Afirma Gene Expression Classifier (GEC) testing (N = 363 nodules from 353 patients) between June 2013 and October 2017 at a single institution, with follow-up data collected until December 2019. Subgroup analysis was performed based on classification of repeat FNA cytology. Outcomes of GEC testing, clinical/sonographic surveillance of unresected nodules, and histopathologic diagnoses of thyroidectomies were compared between three testing approaches: (i) Reflex (MT sent on the basis of the initial Bethesda III/IV FNA), (ii) SemiRestrictive (MT sent if repeat FNA is Bethesda I-IV), and (iii) Restrictive (MT sent only if repeat FNA is Bethesda III/IV) testing approaches. Results: Restricting MT to nodules that remain Bethesda III/IV on repeat FNA would have missed 4 low-risk cancers and 3 noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP) (collectively 2% of the test population) but would have avoided diagnostic surgery for 42 benign nodules (12% of the test population). The Restrictive testing strategy was more specific (delta 0.126 confidence interval [CI 0.093 to 0.159] and 0.129 [CI 0.097 to 0.161], respectively) but less sensitive (delta -0.339 [CI -0.424 to -0.253] and -0.340 [CI -0.425 to -0.255], respectively) than the Reflex and SemiRestrictive approaches for detecting NIFTP or cancer. Conclusions: Repeat FNA cytology can guide the selection of cytologically indeterminate thyroid nodules that warrant MT. The Restrictive model of performing Afirma GEC only on nodules with two separate biopsies showing Bethesda III/IV cytology would reduce the rate of diagnostic surgery for histologically benign nodules while missing only rare low-risk tumors. Given the low but nontrivial risks of thyroidectomy, the higher specificity of the Restrictive testing approach disproportionately outweighs the potential harms.

Combined molecular and histologic end points inform cancer risk estimates for thyroid nodules classified as atypia of undetermined significance

BACKGROUND

Thyroid nodules classified as atypia of uncertain significance (AUS) on fine-needle aspiration cytology are heterogeneous. Prior studies reported a higher risk of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)/cancer among AUS nodules that had cytologic (AUS-C) versus architectural (AUS-A) atypia; however, such studies were generally confined to resected cohorts, introducing bias into risk calculations. The authors hypothesized that combined histologic and molecular end points would permit clinically meaningful calculations of NIFTP/malignancy risk among AUS nodules.

METHODS

The study consisted of 279 thyroid nodules classified as AUS on initial fine-needle aspiration and tested by the Afirma Gene Expression Classifier (GEC) between June 2013 and October 2017. Results of GEC testing and histopathologic diagnoses were stratified by AUS classifiers. The AUS-A category was further subclassified as 1) hypocellular microfollicular or 2) cellular with mixed but predominantly microfollicular architecture. NIFTP/cancer risk was calculated for each subgroup, with the inclusion of unresected nodules that had benign GEC results as low-risk end points comparable to histologically benign nodules.

RESULTS

When only histologic end points were considered, there was no difference in NIFTP/cancer risk (25% vs 23%; P = .82). By using molecular and histologic end points, AUS cases with cytologic atypia trended toward higher NIFTP/cancer risk than AUS-A cases (14% vs 6%; P = .06). Furthermore, AUS-A cases showed a trend toward lower NIFTP/cancer risk for hypocellular microfollicular aspirates (3%) compared with cellular samples that had mixed/predominantly microfollicular architecture (13%; P = .18).

CONCLUSIONS

The inclusion of unresected benign GEC nodules in risk-of-malignancy calculations provides more accurate results, which may be helpful for informing patient management as well as quality improvement in the cytopathology laboratory.

Revised Bethesda System for Reporting Thyroid Cytology: Lessons learned from an appraisal of 5 years of experience in a central hospital

OBJECTIVE

The Bethesda System for Reporting Thyroid Cytology (BSFRTC) is widely adopted in the management of thyroid nodules. The system was updated in 2017, and its impact is the subject of this paper.

METHODS

All thyroid fine needle aspirations from 2016-2020 using the BSFRTC, with follow-up surgical pathology, were reviewed. The risk of neoplasia (RON), risk of malignancy (ROM), RON/ROM ratio, and surgical follow-up rate were determined for each diagnostic category with cytohistological correlation. ROM was calculated in two separate manners, with non-invasive follicular tumours with papillary-like nuclear features (NIFTP) counted as malignant or non-malignant. Sensitivity, specificity, negative and positive predictive values were determined for indeterminate categories: atypia of undetermined significance (AUS), suspicious for follicular neoplasm (SFN), and suspicious for malignancy (SFM).

RESULTS

RON, ROM, and the surgical follow-up rate increased steadily from the benign through intermediate to malignant categories. The omission of NIFTP from malignant lesions reduced the calculated ROM in indeterminate categories and improved the stratification between AUS and SFN. ROM in AUS was distinct from SFN. AUS has a well-balanced sensitivity and specificity favouring a screening rather than a diagnostic category. The calculated RON/ROM was significantly higher in AUS (1.56), compared to SFN (1.03) and SM (1.05), in agreement with current BSRTC management recommendations.

CONCLUSIONS

AUS is an important screening category and should remain with the addition of subcategorisation. RON and surgical follow-up rates are essential quality indicators. The RON/ROM ratio could be utilised to determine appropriate management for each diagnostic category on an institutional basis.

An institutional experience: A retrospective analysis of the effect of transitioning from follicular lesion of undetermined significance to atypia of undetermined significance with subclassified atypia on interobserver concordance, rates of neoplasia, and rates of malignancy

INTRODUCTION

The rate of malignancy (ROM) in thyroid fine needle aspirations (FNA) classified under "atypia of undetermined significance (AUS)/follicular lesion of undetermined significance (FLUS), including Hürthle cell type (HLUS)" category of The Bethesda system for reporting thyroid cytopathology (TBSRTC) in literature is highly variable. The 2018 TBSRTC was updated to note a preferred categorization of AUS cases into subcategories. This study evaluates the impact of AUS subclassification on rates of neoplasia (RON), rates of malignancy (ROM), and cytopathologist (CP) concordance.

METHODS

93 thyroid FNAs previously diagnosed as FLUS or HLUS from January 1, 2013 to December 31, 2014 with subsequent surgical resection were identified. Four CPs reclassified these cases using TBSRTC AUS subcategories of follicular cells with architectural and/or cytologic atypia, predominantly Hürthle cells, and atypical lymphocytes. RON and ROM were calculated for each diagnostic subcategory for each CP.

RESULTS

The original RON and ROM for FLUS cases were 31.4% and 15.1% and were 77.8% and 22.2% for HLUS cases. 10.8% of cases showed diagnostic concordance amongst the four CPs. The most frequently utilized subcategory was architectural atypia. RON ranges for architectural atypia, cytologic atypia, architectural and cytologic atypia, and predominantly Hürthle cells were 28.1% to 35.7%, 0% to 33.3%, 35.3% to 66.7%, and 57.1% to 87.5%. The range of ROM was 13.9% to 16.7%, 0% to 33%, 0% to 42.9%, and 0% to 25%, respectively.

CONCLUSION

RON for AUS predominantly Hürthle cells subcategory was higher than previously reported, which may indicate use for tailored patient management pathways. AUS subclassification can result in significant interobserver variability. Therefore, institutions may consider consensus/quality control sessions to optimize diagnostic concordance.

Are Bethesda III Thyroid Nodules More Aggressive than Bethesda IV Thyroid Nodules When Found to Be Malignant?

The Bethesda classification system for thyroid fine needle aspirate (FNA) is used to predict the risk of malignancy and to guide the management of thyroid nodules. We postulated that thyroid malignancies characterized as Bethesda III on FNA have more aggressive features than those classified as Bethesda IV. A retrospective chart review was performed to identify those who underwent thyroid surgery at a single tertiary hospital setting between 2015 and 2020. Associations between Bethesda category, molecular genetic test results, and histopathologic findings were examined. Out of 628 surgeries that were performed, 199 (54.2%) Bethesda III nodules and 216 (82.8%) Bethesda IV nodules were malignant. Of those that were malignant, 37 (18.6%) and 22 (10.2%) Bethesda III and Bethesda IV nodules showed aggressive features, respectively (p value = 0.014). There was a proportionally increased number of aggressive features in extra-thyroidal extension, lymph nodes metastasis, and all aggressive subtypes of papillary thyroid cancer in the Bethesda III category. Although Bethesda IV nodules are much more likely to be malignant (p value = 0.002), our study suggests that Bethesda III nodules that are resected are more likely to have aggressive features than Bethesda IV nodules, with a statistically significant increase in the solid variant of papillary thyroid cancer and lymph node metastasis.

Differential outcomes of patients with thyroid FNA diagnoses of AUS/FLUS with and without nuclear atypia: The potential need for separation in the Bethesda System

BACKGROUND

In the current version of The Bethesda System (TBS) for thyroid cytopathology, the atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) category has an estimated risk of malignancy of 10% to 30%. Diagnostic criteria include presence of nuclear atypia, suggestive of papillary thyroid carcinoma (PTC), as well as other types of atypia, which can be seen with non-malignant entities. Aim of this study was to investigate differential outcomes of AUS/FLUS, based on specific morphologic criteria, and assess their respective malignancy risks.

METHODS

From a total of 1233 patients undergoing thyroid FNAs between 2010 and 2014 at the University of Washington, 119 had AUS/FLUS without nuclear atypia, and 64 with nuclear atypia. Outcomes for patients with and without nuclear atypia (with the exception of 24 patients lost to follow-up) were evaluated and results were compared.

RESULTS

16/57 (28.1%) patients with AUS/FLUS and nuclear atypia subsequently had carcinomas on thyroidectomy, statistically higher than the 8/102 patients (7.8%, P = .001) without nuclear atypia. When comparing only patients who underwent surgery (n = 63), again those with AUS/FLUS and nuclear atypia had statistically higher rates of carcinoma (16/31, 51.6%), compared to those without (8/32, 25%; P = .0394). Overall, 24/159 (15.1%) of patients with AUS/FLUS had carcinoma on subsequent histology.

CONCLUSION

Malignancy rates for AUS/FLUS were in line with TBS estimated risks. However, our data demonstrate that the presence or absence of nuclear atypia is associated with different malignancy rates, suggesting the possibility that the AUS/FLUS category may best be split into two subcategories with different implied risks of malignancy.

Ultrasound characteristics of thyroid nodules facilitate interpretation of the malignant risk of Bethesda system III/IV thyroid nodules and inform therapeutic schedule

Background

This study was designed to explore whether ultrasound of thyroid nodules facilitates the interpretation of the malignant risk of Bethesda III/IV thyroid nodules to inform further therapies.

Methods

We reviewed patient records in which the results of ultrasound‐guided fine‐needle aspiration (US‐FNA) were classified by the Bethesda III/IV in our institution between January 2016 and June 2018. Studies were retrieved from PubMed, Cochrane Central Register of Controlled Trials, ISI Web of Science, Science Direct, Wiley Online Library, EMBASE, China National Knowledge Infrastructure, WanFang, and Chinese VIP. The odds ratio (OR) was used to measure associations between risk factors and thyroid nodule malignancy.

Results

Fifty‐nine cases of Bethesda III/IV with corresponding surgeries were included, and the malignancy risk was 54.2%. Meta‐analysis revealed irregular borders, solitary nodules, hypoechogenicity, microcalcifications, and being taller than wide, all of which increased the malignancy risk of thyroid nodules. Combined ORs for these factors were 4.08 (95% CI: 2.34‐7.14, P < .001), 2.18 (95% CI: 1.39‐3.42, P = .001), 2.02 (95% CI: 1.35‐3.01, P = .001), 3.21 (95% CI: 2.26‐4.56, P < .001), and 4.35 (95% CI: 3.07‐6.15, P < .001), respectively.

Conclusion

As the risk of malignancy for papillary thyroid carcinoma (PTC) is high, when any one of the five ultrasound features of malignancy were confirmed, repeated FNA is recommended to confirm PTC‐type malignancy, even though nodules were Bethesda III/IV classification. However, repeated FNA should be avoided when none of these ultrasound features are identified because repeated FNA does not contribute to identifying non‐PTC type malignancies, such as follicular thyroid carcinoma and poorly differentiated thyroid carcinoma.

Thyroid Bethesda Atypia of Undetermined Significance or Follicular Lesion of Undetermined Significance (AUS/FLUS): A Heterogenous Group

Background:

The Bethesda system of reporting thyroid cytopathology (BSRTC) was introduced in 2007. The third category of atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) poses difficulties for the pathologist, and different papers have been published varying the risks of malignancy.

Aims:

(1) Evaluation of the cytological features of thyroid lesions according to BSRTC. (2) After resection, correlation with histopathological report to evaluate the risk of malignancy (ROM) and the risk of neoplasm (RON). (3) Division of category III into six subgroups based on cytological findings and assessment of ROM and RON.

Materials and Methods:

A total of 282 patients with diagnosed thyroid lesions underwent fine-needle sampling under ultrasound guidance. Smears were prepared and stained with May–Grunwald–Giemsa stain and Papanicolaou stain.

Results:

Of 282 cases, there were 9 cases (3.1%) of category I, 157 cases (55.8%) of category II, 24 cases (8.5%) of category III, 20 cases (7.1%) of category IV, 14 cases (4.8%) of category V, and 58 cases (20.7%) of category VI. The RON was 60, 17.1, 63.1, 77.7, 91.7, and 98.2% and the ROM was 60, 14.3, 26.3, 38.9, 91.7, and 96.3% in categories I, II, III, IV, V, and VI, respectively. The RON was 0, 75, 50, 100, 66.6, and 100% and the ROM was 0, 25, 50, 100, 16.6, and 0% in subgroups 1, 2, 3, 4, 5, and 6, respectively. We have proposed a system of subgrouping AUS/FLUS that may help to dispel the confusion generated by an AUS/FLUS report, and provide with a more exact and reproducible diagnostic and prognostic tool.

Risk of Malignancy According to the Sub-classification of Atypia of Undetermined Significance and Suspicious Follicular Neoplasm Categories in Thyroid Core Needle Biopsies

The objective of this study was to evaluate the risk of malignancy (ROM) associated with atypia of undetermined significance (AUS) and suspicious follicular neoplasm (SFN) core needle biopsy (CNB) categories after further sub-classification. Data from 2267 thyroid nodules evaluated by ultrasound-guided CNB, from January to December 2015, were retrospectively reviewed. AUS nodules (n = 556) were sub-classified as follows: (1) architectural atypia (AUS-A; n = 369, 66.4%), (2) cytologic atypia (AUS-C; n = 35, 6.3%), (3) cytologic/architectural atypia (AUS-C/A; n = 85, 15.3%), or (4) oncocytic atypia (AUS-O; n = 67, 12.1%). SFN nodules (n = 172) were sub-classified as follows: (1) architectural atypia only (SFN-A; n = 110, 64%), (2) cytologic/architectural atypia (SFN-C/A; n = 24, 14%), or (3) oncocytic atypia (SFN-O; n = 38, 22%). Diagnostic surgery was performed in 162 (30.2%) AUS cases and 105 (61%) SFN cases. The ROM of each sub-category was evaluated. The overall ROM was 15.3-52.5% in AUS nodules and 35.5-58.1% in SFN nodules. The ROM was higher in the AUS-C (22.9-88.9%) and AUS-C/A (32.9-90.3%) groups than AUS-A (11.9-40%) and AUS-O (7.5-41.7%). In the SFN category, ROM in the SFN-C/A group was also higher than SFN-A or SFN-O (37.5-75%, 40-57.9%, and 21.1-47.1%, respectively). Our study shows that the ROM was higher in AUS or SFN sub-categories with cytologic atypia than those without cytologic atypia. Because of the heterogeneous nature of AUS and SFN categories, sub-classification may be a more effective approach for risk stratification, allowing optimal management of patients with thyroid nodules.

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

OBJECTIVES

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

STUDY DESIGN

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

CONCLUSION

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

Evaluation of selected ultrasound features of thyroid nodules with atypia of undetermined significance/follicular lesion of undetermined significance for the Bethesda reporting system for thyroid cytology

Background and objective

The risk of malignancy from “atypia of undetermined significance/follicular lesion of undetermined significance” (AUS/FLUS) is estimated to lie between 5% and 15%; however, some authors suggest that the risk of malignancy in AUS/FLUS depends upon specific clinical situations. This was a retrospective study which aimed to determine the incidence and risk of thyroid cancer (TC) based upon selected ultrasound features from patients with thyroid nodules (TN) classified as AUS/FLUS.

Methods

Univariate and multivariate logistic regression analyses were used to identify significant associations between ultrasound features and the risk of TC.

Results

Of 127 patients with TN classified as AUS/FLUS who underwent thyroidectomy, 114 (89.8%) had benign disease while 13 (10.2%) had TC. Univariate analysis identified several significant predictors for TC (all p<0.05), including microcalcifications, hypoechogenicity, the prevalence of irregular margins, a taller rather than a wide form, high vascularity, and fast tumor growth. Multivariate analysis further showed that microcalcifications (odds ratio =21.37; p=0.024) and fast growth (odds ratio =22.70; p=0.021) were significant and independent factors associated with the risk of developing TC.

Conclusion

Microcalcifications and fast growth of the TN could therefore be used as predictive factors for the development of TC in patients with AUS/FLUS.

Subclassification of Bethesda Atypical and Follicular Neoplasm Categories According to Nuclear and Architectural Atypia Improves Discrimination of Thyroid Malignancy Risk

BACKGROUND

Although The Bethesda System for Reporting Thyroid Cytopathology has provided clinicians with a standardized classification scheme for the diagnosis of thyroid fine-needle aspiration cytology (FNAC) specimens, the indeterminate categories of Bethesda III (B3)-atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS)-and Bethesda IV (B4)-follicular neoplasm/suspicious for follicular neoplasm (FN/SFN)-continue to pose challenges with regards to ideal diagnostic and therapeutic management. Having previously demonstrated the presence of nuclear atypia as a high-risk subgroup in B3, the objective of this study was to evaluate the malignancy rates in the B4 subgroup with nuclear atypia.

METHODS

A retrospective review of all thyroid FNACs diagnosed as B4 (FN/SFN) between 2008 and 2015 was conducted at a tertiary referral center in Singapore. Data on patient demographics, sonographic features, and final histological diagnosis were collected. This was compared to data from a previous analysis on all nodules diagnosed as B3 (AUS/FLUS) over a similar period.

RESULTS

A total of 137/309 (44.3%) and 88/111 (79.3%) FNACs diagnosed as B3 and B4, respectively, underwent surgical excision yielding final histopathological diagnoses. The malignancy rate of B4 was 31/88 (35.2%) compared to B3, which was 37/137 (27.0%). Subclassification based on the presence of architectural versus nuclear atypia showed significantly higher malignancy rates in B4 nodules with nuclear atypia (21.8% vs. 57.6%; p < 0.01). These findings corroborate previous results within the B3 category (malignancy rate of 14.7% vs. 36.8%; p < 0.01). The only sonographic features predictive of malignancy were the presence of macrocalcifications in B4 compared to irregularity of margins in B3.

CONCLUSION

The presence of nuclear atypia identifies subgroups with significant differential malignancy risks within both the B3 and B4 categories. This supports the notion that subclassification is a useful risk stratification tool that can guide diagnostic and therapeutic management of indeterminate thyroid nodules with heterogenous risk profiles.

The presence of papillary features in thyroid nodules diagnosed as atypia of undetermined significance or follicular lesion of undetermined significance increases cancer risk and should influence treatment

BACKGROUND

The objective of this study was to evaluate the influence of papillary features on risk of malignancy (ROM) within the Atypia of Undetermined Significance or Follicular Lesion of Undetermined Significance (AUS-FLUS) Bethesda System for Reporting Thyroid Cytopathology (BSRTC) diagnostic category.

METHODS

A Retrospective review of cases with an AUS-FLUS diagnosis that underwent a thyroidectomy was carried out, and cases were subcategorized based upon the presence of papillary features.

RESULTS

For the entire study population there were 93 (22%) of 427 FNAB specimens that had an AUS-FLUS diagnosis, and a 32% associated ROM. Papillary features were identified in 44 FNAB specimens (47% of the AUS-FLUS cases or 10% of the entire study population), and when present had a 45% ROM. The 49 FNAB specimens (53%) that did not exhibit papillary features had a significantly lower ROM (20%) than those that did have papillary features (p = 0.0069).

CONCLUSIONS

The presence of papillary features in a thyroid FNAB with an AUS-FLUS diagnosis is common, and is associated with a higher ROM than is currently suggested by the BSRTC.

The impact of noninvasive follicular thyroid neoplasm with papillary-like nuclear features on the rate of malignancy for atypia of undetermined significance subcategories

BACKGROUND

The recent revision in terminology, with noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) replacing noninvasive follicular variant of papillary thyroid carcinoma, has reclassified the clinically indolent tumor as nonmalignant. The objective of this study was to evaluate the impact of this change on the rate of malignancy (ROM) for subcategories of an atypia of undetermined significance (AUS) diagnosis on fine-needle aspiration (FNA) cytology.

METHODS

Consecutive thyroid FNAs interpreted as AUS over a period of 4 years were retrospectively analyzed. The ROM for AUS subcategories, including atypia of undetermined significance with nuclear atypia (AUS-N), atypia of undetermined significance with a microfollicular pattern (AUS-F), atypia of undetermined significance with nuclear atypia and a microfollicular pattern (AUS-N/F), atypia of undetermined significance with Hürthle cells (AUS-H), and atypia of undetermined significance, not otherwise specified (AUS-NOS), were analyzed.

RESULTS

Of the 426 nodules interpreted as AUS, 244 were surgically excised. The incidence of NIFTP in each subcategory was as follows: 18% for AUS-N, 18% for AUS-F, 9% for AUS-N/F, 3% for AUS-H, and 0% for AUS-NOS. After the reclassification of NIFTP as nonmalignant, the ROM based on histologic follow-up significantly decreased from 43% to 26% for AUS-N (P < .001) and from 29% to 10% for AUS-F (P = .008). The ROM for AUS-N remained significantly higher than the ROM for AUS-F (P = .030).

CONCLUSIONS

A subset of resected AUS nodules can be reclassified as NIFTP, and that significantly decreases the ROM, especially for AUS-N and AUS-F. Nonetheless, AUS-N still harbors a substantially higher ROM than AUS-F. Cancer Cytopathol 2018;126:309-16. © 2018 American Cancer Society.

Fine Needle Aspiration in the Investigation of Thyroid Nodules

BACKGROUND

Thyroid nodules are a common finding in Germany. Most are benign; thyroid cancer is very rare. The challenge for the physician is to diagnose malignant tumors early. Fine needle aspiration is an important tool for this purpose.

METHODS

This review is based on pertinent articles (1980-2014) retrieved by a selective search in PubMed and on the current recommendations of guidelines issued by the specialty societies in Germany and abroad.

RESULTS

Clinical, ultrasonographic, and scintigraphic criteria are used to identify high-risk nodules, which are then further studied by fine needle aspiration. Important ultrasonographic criteria for malignancy are low echodensity (positive predictive value [PPV]: 1.85), microcalcifications (PPV: 3.65), irregular borders (PPV: 3.76), and intense vascularization. Fine needle aspiration of the thyroid gland is an inexpensive and technically straight - forward diagnostic procedure that causes little discomfort for the patient. It helps prevent unnecessary thyroid surgery and is used to determine the proper surgical strategy if malignancy is suspected. The cytological study of fine needle aspirates enables highly precise diagnosis of many tumor entities, but follicular neoplasia can only be diagnosed histologically. In the near future, molecular genetic methods will probably extend the diagnostic range of fine needle aspiration beyond what is currently achievable with classic cytology.

CONCLUSION

Fine needle aspiration biopsy of the thyroid gland in experienced hands is an easily performed diagnostic procedure with very little associated risk. It should be performed on ultrasonographically suspect nodules for treatment stratification and before any operation for an unclear nodular change in the thyroid gland.

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.

Qualifiers of atypia in the cytologic diagnosis of thyroid nodules are associated with different Afirma gene expression classifier results and clinical outcomes

BACKGROUND

Thyroid nodules with atypia of undetermined significance (AUS) on fine‐needle aspiration (FNA) have a low risk of malignancy that appears to vary based on specific features described in the AUS diagnosis. The Afirma gene expression classifier (GEC) is a molecular test designed to improve preoperative risk stratification of thyroid nodules, but its performance for different patterns of AUS has not been defined. The objective of this study was to assess GEC results and clinical outcomes in AUS nodules with architectural atypia (AUS‐A), cytologic atypia (AUS‐C) or both (AUS‐C/A).

METHODS

This was a retrospective review of all thyroid nodules with AUS cytopathology that underwent GEC testing at the authors' institution over a period of >4 years.

RESULTS

In 227 nodules that had AUS cytology results and Afirma GEC testing, the rate of benign GEC results was higher in AUS‐A nodules (70 of 107; 65%) than in AUS‐C/A nodules (25 of 65; 38%; P = .0008), and AUS‐C nodules exhibited an intermediate rate of benign results (27 of 55 nodules; 59%). The risk of cancer among patients who had GEC‐suspicious nodules, 86% of whom underwent resection, was 19% (6 of 25) for AUS‐A nodules compared with 57% (21 of 37) for AUS‐C/A nodules (P = .003) and 45% (10 of 22) for AUS‐C nodules (P = .07). In nodules that had an indeterminate repeat cytology result, no difference was observed in the rate of benign GEC results or in the malignancy rate compared with nodules that had a single cytology result.

CONCLUSIONS

The performance characteristics of Afirma GEC testing vary, depending on qualifiers of cytologic atypia. Recognition of these differences may enable clinicians to provide improved counseling and treatment recommendations to patients. Cancer Cytopathol 2017;125:313–322. © 2017 American Cancer Society.

Thyroid nodules with atypia of undetermined significance cytology and Afirma gene expression classifier (GEC) testing are analyzed based on the presence of architectural, cytologic, or both cytologic and architectural atypia. Nodules with architectural atypia are the most likely to have a benign GEC result and least likely to be malignant, suggesting that clinicians should be aware of these cytologic qualifiers when advising patients regarding GEC testing and the risk of malignancy.

AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS, AMERICAN COLLEGE OF ENDOCRINOLOGY, AND ASSOCIAZIONE MEDICI ENDOCRINOLOGI MEDICAL GUIDELINES FOR CLINICAL PRACTICE FOR THE DIAGNOSIS AND MANAGEMENT OF THYROID NODULES--2016 UPDATE

Thyroid nodules are detected in up to 50 to 60% of healthy subjects. Most nodules do not cause clinically significant symptoms, and as a result, the main challenge in their management is to rule out malignancy, with ultrasonography (US) and fine-needle aspiration (FNA) biopsy serving as diagnostic cornerstones. The key issues discussed in these guidelines are as follows: (1) US-based categorization of the malignancy risk and indications for US-guided FNA (henceforth, FNA), (2) cytologic classification of FNA samples, (3) the roles of immunocytochemistry and molecular testing applied to thyroid FNA, (4) therapeutic options, and (5) follow-up strategy. Thyroid nodule management during pregnancy and in children are also addressed. On the basis of US features, thyroid nodules may be categorized into 3 groups: low-, intermediate-and high-malignancy risk. FNA should be considered for nodules ≤10 mm diameter only when suspicious US signs are present, while nodules ≤5 mm should be monitored rather than biopsied. A classification scheme of 5 categories (nondiagnostic, benign, indeterminate, suspicious for malignancy, or malignant) is recommended for the cytologic report. Indeterminate lesions are further subdivided into 2 subclasses to more accurately stratify the risk of malignancy. At present, no single cytochemical or genetic marker can definitely rule out malignancy in indeterminate nodules. Nevertheless, these tools should be considered together with clinical data, US signs, elastographic pattern, or results of other imaging techniques to improve the management of these lesions. Most thyroid nodules do not require any treatment, and levothyroxine (LT4) suppressive therapy is not recommended. Percutaneous ethanol injection (PEI) should be the first-line treatment option for relapsing, benign cystic lesions, while US-guided thermal ablation treatments may be considered for solid or mixed symptomatic benign thyroid nodules. Surgery remains the treatment of choice for malignant or suspicious nodules. The present document updates previous guidelines released in 2006 and 2010 by the American Association of Clinical Endocrinologists (AACE), American College of Endocrinology (ACE) and Associazione Medici Endocrinologi (AME).

The 5-tiered categorization system for reporting cytology is sufficient for management of patients with thyroid nodules compared to the 6-tiered Bethesda system

To analyze whether the 5-tiered categorization system without the atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS) category is sufficient compared to the 6-tiered Bethesda system. This IRB-approved retrospective study was waived informed consent. The pre-Bethesda period was from March 2008 to December 2008 and the Bethesda period was from January 2012 to January 2013. Of 4677 nodules ≥10 mm with initial ultrasonography-guided fine-needle aspiration, 2553 nodules were from the pre-Bethesda period and 1754 nodules were from the Bethesda period. The utilization and malignancy rates of each category were compared between the two periods. The utilization rate of the benign category decreased from 67.7 % in the pre-Bethesda period to 60.0 % in the Bethesda period (p = 0.001). In the pre-Bethesda period, the malignancy rates of the non-diagnostic, benign, suspicious follicular neoplasm/Hürthle cell neoplasm, suspicious for malignancy, and malignancy categories were 3.8, 1.9, 25, 78.8, and 99.7 %, respectively. The malignancy rate of the benign category decreased from 1.9 to 0.3 % after the Bethesda system (p < 0.001). The utilization and malignancy rates of the AUS/FLUS category were 7 and 22.8 %. When the AUS/FLUS category was included in the benign category, the malignancy rate became 2.6 % which was not significantly different from 1.9 % in the pre-Bethesda period (p = 0.189). The malignancy rates of other categories were not significantly different. The 5-tiered categorization system without the AUS/FLUS category for reporting cytology was sufficient for management of patients with thyroid nodules compared to the 6-tiered categorization of the Bethesda system.

Combined use of conventional smear and liquid-based preparation versus conventional smear for thyroid fine-needle aspiration

The purpose of the study was to compare the diagnostic utility of the combined conventional smear (CS) and liquid-based preparation (LBP) compared to CS with respect to the non-diagnostic rate, the atypia of undetermined significance (AUS) or follicular lesion of undetermined significance (FLUS) rate, and the diagnostic performances for malignancy. This retrospective study was approved by the Institutional Review Board, and the need to obtain informed consent was waived. In our institution, thyroid FNAs were processed with CS before October 2012, and LBP has been used in combination with CS after October 2012. On-site evaluation for the adequacy of CS was not performed. This study included nodules 5 mm or larger with FNAs performed by faculties: 811 nodules in 773 patients for CS, and 926 nodules in 894 patients for combined CS and LBP. Nodules with surgery or either benign or malignancy cytology on initial or repeat FNA were regarded to have the reference standards needed to calculate diagnostic performances. The proportion of Bethesda categories and diagnostic performances were compared between the two groups with z test. The non-diagnostic rate, the AUS or FLUS rate, and the diagnostic performances for malignancy were similar (All P > 0.05). The follicular neoplasm (FN) or suspicious for FN rate decreased from 1.2 to 0.3 % (P = 0.034). The benign rate increased from 51.4 to 57.0 % (P = 0.019). Combined CS and LBP decreased FN or suspicious for FN diagnoses, and increased benign diagnoses compared to CS with comparable non-diagnostic rates and AUS or FLUS rates, and comparable diagnostic performances.

Cytological diagnosis of pediatric thyroid nodule in perspective of the Bethesda System for Reporting Thyroid Cytopathology

Background:

Thyroid nodule is one of the most common endocrinopathies occurring children and adolescents. Though thyroid nodule is rare in the pediatric age group, the rate of malignancy is much higher in this age group compared to adult population.

Aim:

The objective is to study the application of The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) in pediatric patients and compare the findings with histology.

Materials and Methods:

A total of 218 cases younger than 18 years were studied in a 4-year period from August 2010 to July 2014. The smears were categorized according to TBSRTC into six categories — Nondiagnostic, benign, atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS), suspicious for follicular neoplasm (SFN), suspicious for malignancy (SM), and malignancy.

Results:

Out of 218 cases, 33 were males and 185 were females. Histological follow-up was available in 44 cases. The diagnosis according to TBSRTC included 12 (5.5%) nondiagnostic, 151 (69.26%) benign, 23 (10.5%) AUS/FLUS, 18 (8.2%) SFN, 5 (2.3%) SM, and 9 (4.1%) malignancy cases. On histological follow-up, the rate of malignancy in each category was 0%, 0%, 8.3%, 10% 100%, and 100%, respectively.

Conclusion:

The study demonstrates that TBSRTC in pediatric thyroid nodule is as sensitive and specific as in adults, especially with 100% accuracy in the diagnosis of benign and malignant categories.

Diagnostic Thyroidectomy May Be Preferable in Patients With Suspicious Ultrasonography Features After Cytopathology Diagnosis of AUS/FLUS in the Bethesda System

Atypia/follicular lesion of undetermined significance (AUS/FLUS) is a new category in the Bethesda System for Reporting Thyroid Cytopathology (BSRTC) for which repeat fine-needle aspiration cytology (FNAC) is recommended. The aim of this study was to identify specific ultrasonography and clinical predictors of malignancy in a subset of thyroid nodules associated with cytology diagnoses of AUS/FLUS.Between January 2011 and December 2102, 5440 patients underwent thyroid surgery at our institution. Of these, 213 patients were diagnosed AUS/FLUS at the preoperative cytopathology diagnosis. The frequency of FNAC and ultrasonography images was compared between patients with cancerous and benign tumors based on their final pathology.Of the 213 patients, 158 (74.2%) were diagnosed with thyroid carcinoma in their final pathology reports. In univariate and multivariate analyses, the frequency of FNAC was not significantly correlated with the cancer diagnosis. Hypoechogenicity (odds ratio 2.521, P = 0.007) and microcalcification (odds ratio 3.247, P = 0.005) were statistically correlated with cancer risk.Although AUS/FLUS in cytopathology is recommended for repeating FNAC in BSRTC, we proposed that thyroid nodules with ultrasonography findings that suggest the possibility of cancer should undergo thyroidectomy with diagnostic intent.

The Impact of Noninvasive Follicular Variant of Papillary Thyroid Carcinoma on Rates of Malignancy for Fine-Needle Aspiration Diagnostic Categories

BACKGROUND

Increased recognition of the indolent nature of noninvasive follicular variant of papillary thyroid carcinoma (NFVPTC) along with greater insight into the molecular alterations of these tumors has prompted endocrine pathologists to question whether these tumors warrant a diagnosis of carcinoma. However, a change in terminology would affect the rates of malignancy of fine-needle aspiration (FNA) diagnostic categories. Therefore, the aim of this study was to determine the percentage decrease in associated risk of malignancy for each FNA diagnostic category if NFVPTCs were no longer termed carcinomas.

METHODS

We evaluated a cohort of 655 FNAs with subsequent resection specimens over a 22-month time period. The diagnoses of the preceding FNAs were recorded according to the Bethesda System for Reporting Thyroid Cytopathology. For cases with more than one preceding FNA, the FNA diagnosis associated with the highest risk of malignancy was identified. Slides for all resection specimens with a diagnosis of FVPTC were reviewed to identify noninvasive tumors. By definition, all of these tumors were encapsulated, partially encapsulated, or well circumscribed and lacked any indication of infiltrative growth, capsular penetration, or lymphovascular invasion.

RESULTS

Our cohort of 655 FNAs with subsequent resection specimens included 53 (8.1%) nondiagnostic (ND), 167 (25.5%) benign, 97 (14.8%) atypia/follicular lesion of undetermined significance (AUS/FLUS), 88 (13.4%) suspicious for follicular neoplasm (SFN), 94 (14.4%) suspicious for malignancy (SUS), and 156 (23.8%) malignant cases (POS). Surgical resections demonstrated benign findings in 309 (47.2%) and malignant tumors in 346 (52.8%), including 85 NFVPTCs accounting for 24.6% of malignancies. Our rates of malignancy for ND, benign, AUS/FLUS, SFN, SUS, and POS were 18.9%, 13.2%, 39.2%, 45.5%, 87.2%, and 98.7%, respectively. If NFVPTC were no longer termed carcinoma, these rates would drop to 17.0% (10% decrease), 5.4% (59% decrease), 21.6% (45% decrease), 37.5% (18% decrease), 45.7% (48% decrease), and 93.6% (5% decrease), respectively.

CONCLUSION

Our findings demonstrate that if terminology were changed and NFVPTCs were not considered carcinomas, the rates of malignancy for FNA diagnostic categories would be substantially decreased, with the most clinically significant decrease seen in the SUS category, which demonstrated a relative decrease of nearly 50%.

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.

What is atypia? Use, misuse and overuse of the term atypia in diagnostic cytopathology

The term "atypical" was introduced by the founder of modern cytodiagnosis, Dr. George N. Papanicolaou, to convey a very low suspicion of (pre)malignancy. Despite controversies concerning its ambiguous and imprecise definition and its uncertain optimal use, the term "atypia" has continued to be used in cytopathology, and has recently been increasingly used in standardized nongynecologic cytopathology diagnostic reporting terminologies. Its increasing use suggests that "atypia" continues to be a useful category to fill the gap between what we can recognize as entirely normal (including reactive changes) and what we can recognize as clearly abnormal (premalignant or malignant). However, this diagnosis should be used parsimoniously, since the potential overuse of "atypia" diagnoses can lead to the erosion of clinicians' confidence in cytopathology, their misunderstanding of the cytopathology report, and to an increase the clinicians' diagnostic uncertainty, with negative consequences on patients' satisfaction and wellbeing, and on health care costs. A clinically meaningful, standardized cytodiagnostic category of "atypia" requires a narrow definition, quantitative criteria, agreed-upon reference images, a clear clinical meaning (likelihood of underlying malignancy or premalignancy) and, ideally, well-defined management options. The successful implementation of such a standardized "atypia" diagnostic category requires continuous education of cytology professionals and quality assurance efforts to monitor its use. The interobserver variability and potential excessive use of the diagnosis of "atypia" may be reduced by considering and addressing the major factors involved in its variable use, namely the quality of the sample, the definition of "atypia", the education/training of the cytologist/pathologist, and cytologist/pathologist-related "supracytologic" factors.

Next-generation sequencing improves the diagnosis of thyroid FNA specimens with indeterminate cytology

AIMS

The assessment of thyroid nodules is a common clinical challenge. Fine-needle aspiration (FNA) is the standard pre-operative tool for thyroid nodule diagnosis. However, up to 30% of the samples are classified as indeterminate. This often leads to unnecessary surgery. In this study, we evaluated the added value of next-generation sequencing (NGS) for helping in the diagnosis of FNA samples.

METHODS AND RESULTS

We analysed retrospectively 34 indeterminate FNA samples for which surgical resection was performed. DNA was obtained from cell blocks or from stained smears and subjected to NGS to analyse mutations in 50 genes. Mutations in BRAF, NRAS, KRAS and PTEN, that are known to be involved in thyroid cancer biology, were detected in seven FNA samples. The presence of a mutation in these genes was a strong indicator of cancer because five (71%) of the mutation-positive FNA samples had a malignant diagnosis after surgery. Moreover, there was only an 8% cancer risk in nodules with an indeterminate cytological diagnosis but with a negative molecular test.

CONCLUSION

This study demonstrates that thyroid FNA can be analysed successfully by NGS. The detection of mutations known to be involved in thyroid cancer improves the sensitivity of thyroid FNA diagnosis.

Thyroid atypia of undetermined significance or follicular lesion of undetermined significance: an indispensable Bethesda 2010 diagnostic category or waste garbage?

OBJECTIVE

The Bethesda System for Reporting Thyroid Cytopathology (BSRTC) was introduced in thyroid cytology in 2007 and is now generally accepted. BSRTC categories include a morphologic description and risk of malignancy as well as follow-up suggestions in each group. However, the category entitled 'atypia of undetermined significance or follicular lesion of undetermined significance' (AUS/FLUS) is problematic. This category is heterogeneous and has been overused so far.

STUDY DESIGN

Twenty-six studies were included in a meta-analysis. In addition to AUS/FLUS percentage, we analysed repeated AUS/FLUS percentage, cytological and histological correlations, and risk of malignancy and neoplasm for AUS/FLUS. Furthermore, stratification, inter- and intra-observer variability, and the possibility of a switch to another category and its clinical consequences were reviewed.

RESULTS

Out of a total of 81,833 cases, AUS/FLUS accounted for 10.9%, with a 34% risk of malignancy. Persistent AUS/FLUS was found in 21.6% in repeated cytology. Cytohistological correlation was analysed from 16 studies (4,964 cases), revealing 10.4% as AUS/FLUS and a 21.5% risk of malignancy.

CONCLUSIONS

An AUS/FLUS category seems to be currently reasonable with clearly defined cytomorphological criteria which do not correspond unequivocally with those of the other categories. An AUS/FLUS category is justified and possible means of its improvement with immunohistochemistry, molecular analysis and imaging are discussed.

Malignancy rate of thyroid nodules defined as follicular lesion of undetermined significance and atypia of undetermined significance in thyroid cytopathology and its relation with ultrasonographic features

Fine-needle aspiration biopsy (FNAB) has been widely accepted as the most accurate, safe, and cost-effective method for evaluation of thyroid nodules. The most challenging category in FNAB is atypia of undetermined significance (AUS) and follicular lesion of undetermined significance (FLUS). The Bethesda system (BS) recommends repeat FNAB in that category due to its low risk of malignancy. In our study, we aimed to investigate the malignancy rate of thyroid nodules of AUS and FLUS and whether there were different malignancy rates among the different patterns in this category, and to evaluate the presence of biochemical, clinical, and echographic features possibly predictive of malignancy related to AUS and FLUS. Data of 268 patients operated for AUS and FLUS cytology were screened retrospectively. Ultrasonographic features and thyroid function tests, thyroid antibodies, scintigraphy, and histopathological results were evaluated. Of the 268 patients' results, 276 nodules are evaluated. Malignancy rates were 24.3 % in the AUS group, 19.8 % in the FLUS group, and 22.8 % in both groups. In the evaluation of all nodules, the predictive features of malignancy are hypoechogenicity and peripheral vascularization of the nodule. We determined that the malignancy rates in these nodules are higher than that in the literature rate. This high ratio may be due to the fact that we studied only patients who underwent surgery. The ultrasonographic features alone may be insufficient to predict the malignancy; therefore, all the clinical and ultrasonographic features must be considered in the evaluation of the thyroid nodules. In addition, we think that the recommended management of repeat FNAB in these groups must be reconsidered with the clinical and ultrasonographic features.

Diagnosis of atypia/follicular lesion of undetermined significance: An institutional experience

BACKGROUND

The overall malignancy rate for the thyroid fine-needle aspiration (FNA) diagnosed as atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) ranges from 5% to 30%. In this study, we present our institutional experience with thyroid nodules diagnosed as AUS/FLUS and further stratified into subcategories. In addition, we also assessed the significance of various clinicopathologic factors that may influence AUS/FLUS diagnoses and their outcomes.

DESIGN

A search of our laboratory information system was performed to identify all in-house thyroid FNA cases diagnosed as AUS/FLUS from 2008 to 2012. The data were collected and characterized by patient demographic information, cytopathology diagnosis with sub-classifiers and follow-up.

RESULTS

The case cohort included 457 cases diagnosed as AUS/FLUS. These were further sub-classified into one of six subcategories depending on the cytomorphologic findings and suspicion for or against a neoplastic process. Of the 457 cases, repeat FNA and/or surgical follow-up was available in 363 cases. There were 182 (39.8%) cases with cytologic follow-up only; 18 (9.9%) remained as AUS/FLUS, while 158 (86.8%) were re-classified with the majority being benign (142 cases). Histologic follow-up was available in 181 (39.6%) cases. There were 60 malignant cases confirmed by surgical excision, with an overall malignancy rate of 33.1%. The malignancy rate was 38.8% for cases with a repeat FNA versus 25.6% for cases that went directly to surgery without a repeat FNA. Papillary thyroid carcinoma accounted for 93.3% (56 cases) of the malignant cases.

CONCLUSION

Based on our study, even though the malignancy rate of AUS/FLUS cases is similar to those reported for cases diagnosed as follicular neoplasm/suspicious for follicular neoplasm, we are of the belief that these comparable malignancy rates are a product of better clinical management and selection of patients diagnosed as AUS/FLUS for surgery after a repeat FNA.

Results of retrospective classification of thyroid FNAs according to the Bethesda system: would this have improved accuracy?

OBJECTIVES

To retrospectively reclassify the results of fine needle aspiration (FNA) cytology at our institution according to the Bethesda system for reporting thyroid cytopathology (TBSRTC), and to determine whether the introduction of the new classification system would have influenced the diagnostic accuracy compared with our existing system in which suspicious/indeterminate categories (categories III-IV) are managed according to clinical findings and cytopathologists' recommendations.

METHODS

FNAs performed under ultrasound guidance between 2001 and 2012, and subsequently verified by histology or repeat FNA and follow-up, were reviewed and retrospectively reclassified according to TBSRTC.

RESULTS

Among a total of 1310 histologically verified FNAs, the positive predictive values (%) for malignancy and neoplasia (carcinoma + follicular adenomas) for category I-VI according to the TBSRTC were 5.7/11.3, 2.6/5.5, 14.4/34.2, 23.6/55.0, 57.0/64.5 and 92.2/94.2, respectively. Although all the categories predict malignancy closely, the difference in malignancy rate between categories III and IV was not statistically significant; however, the difference in total neoplasia rate reached statistical significance. When patients with cytological and clinical follow-up were included, the malignancy rated dropped in category I to 2.4%, whereas, in category III, it remained at 13%. Repeat FNA instead of direct surgery spared half of the patients from surgery. The cytopathologists' recommendations for histological verification in category III were associated with an insignificant increase in malignancy rate, but the total neoplasia rate reached 57.5%.

CONCLUSIONS

At our institution, the application of the TBSRTC did not improve the diagnostic accuracy for the detection of malignancy compared with current practice. In selected cases with cytological results falling into category III (according to clinical data and cytopathologists' opinions), direct lobectomy seems to be justified.

Introducing the reporting system for thyroid fine-needle aspiration cytology according to the new guidelines of the Japan Thyroid Association

The Japan Thyroid Association (JTA) recently published new guidelines for clinical management of thyroid nodules. This paper introduces their diagnostic system for reporting thyroid fine-needle aspiration cytology. There are two points where the new reporting system that differs from existing internationally-accepted ones. The first is the subclassification of the so-called indeterminate category, which is divided into 'follicular neoplasm' and 'others'. The second is the subclassification of follicular neoplasm into 'favor benign', 'borderline' and 'favor malignant'. It is characterized by self-explanatory terminologies as to histological type and probability of malignancy to establish further risk stratification as well as to facilitate communication between clinicians and cytopathologists. The different treatment strategies adopted for thyroid nodules is deeply influenced by the particular diagnostic system used for thyroid cytology. In Western countries all patients with follicular neoplasms are advised to have immediate diagnostic surgery while patients in Japan often undergo further risk stratification without immediate surgery. The JTA diagnostic system of reporting thyroid cytology is designed for further risk stratification of patients with indeterminate cytology. If a surgeon applies diagnostic lobectomy to all patients with follicular neoplasm unselectively, this subclassification of follicular neoplasm has no practical meaning and is unnecessary. Cytological risk stratification of follicular neoplasms is optional and cytopathologists can choose either a simple 6-tier system without stratification of follicular neoplasm or a complicated 8-tier system depending on their experience in thyroid cytology and clinical management.

Subclassification of "atypia of undetermined significance" in thyroid fine-needle aspirates

To identify the subtypes of atypia of undetermined significance (AUS) that confers a different magnitude for the risk of malignancy (RM), thyroid fine-needle aspiration (FNA) cases carrying a diagnosis of "atypical follicular cells" or "follicular lesion" with surgical pathology followup were included in this study. The direct smears of the aspirates were rereviewed and subclassified into four subgroups based on cytomorphology: AUS cannot exclude follicular neoplasm (AUS-FN), AUS cannot exclude Hürthle cell neoplasm (AUS-HCN), AUS cannot exclude papillary carcinoma (AUS-PTC) and AUS, not otherwise specified (AUS-NOS). Based on the followup histopathologic findings, RM not including papillary microcarcinoma (PMC), RM including PMC and the risk of neoplasm (RN) were calculated for each of the four AUS subgroups. A total of 138 AUS cases were subclassified into AUS-NOS (48), AUS-PTC (41), AUS-FN (32), and AUS-HCN (17). RM not including PMC was 32% for AUS-PTC (P < 0.001), 25% for AUS-FN, 8% for AUS-NOS, 0% for AUS-HCN, and 18% for all AUS cases. RM including PMC was 54% for AUS-PTC (P < 0.001), 34% for AUS-FN, 19% for AUS-NOS, 18% for AUS-HCN, and 33% for all AUS cases. RN was 63% for AUS-PTC (P = 0.05), 81% for AUS-FN (P < 0.01), AUS-HCN 53%, AUS-NOS 44% and 59% for all cases. In our study, subclassification enabled us to further divide AUS cases into high- and low-risk groups. The high-risk group includes AUS-PTC with a significantly higher risk of malignancy and AUS-FN with a significantly higher risks of neoplasm. AUS-HCN and AUS-NOS subgroups demonstrate a lower risk of malignancy of <10%.

Follicular lesion of undetermined significance in thyroid FNA revisited

Controversy exists regarding the validity of follicular lesion of undetermined significance (FLUS), an indeterminate diagnostic category of The Bethesda System for Reporting Thyroid Cytopathology (BSRTC). According to BSRTC, FLUS carries a 5-15% risk of cancer. This study was designed to determine if cytomorphology could stratify FLUS into subgroups with different risks of malignancy. Reports of 127 consecutive FNAs reported as FLUS with subsequent tissue diagnoses were evaluated for the presence of various cytologic features and the results were correlated with histological diagnoses. FLUS cases with focal nuclear atypia (nuclear overlap/crowding, nuclear grooves/membrane irregularities, nuclear enlargement, and/or nuclear pseudoinclusions) were more frequently malignant on excision whereas those with architectural atypia (microfollicles) were more often benign on excision (P < 0.05). The presence of any one or more of these nuclear features increased the risk of carcinoma in subsequent thyroid resection. Papillary carcinomas predominated in excised FLUS cases with focal nuclear atypia whereas most FLUS with architectural atypia were adenomas or hyperplastic nodules on histological evaluation. BSRTC recommends that thyroid aspirates containing follicular cell nuclear and/or architectural atypia insufficient for a diagnosis of suspicious for follicular neoplasm, suspicious for malignancy or malignant be classified as FLUS. Our findings indicate that FLUS cases with focal nuclear atypia carry a risk for malignancy that is substantially higher than that assigned to FLUS and are best classified as suspicious. FLUS cases lacking these atypical nuclear features have a risk for malignancy that approximates the risk BSRTC has assigned to FLUS.

Assessment of malignancy for atypia of undetermined significance in thyroid fine-needle aspiration biopsy evaluated by whole-slide image analysis

Atypia of undetermined significance (AUS) in thyroid fine-needle aspiration (FNA) has a low to intermediate incidence of malignancy, and objective criteria could allow for improved assessment of malignancy. Consecutive thyroid FNA AUS cases with surgical excision were selected. Whole-slide images (WSIs) were evaluated for basic criteria by image analysis, including total groups and nuclear/cytoplasmic (N/C) ratio. The 44 cases encompassed 23 benign and 21 malignant entities. Seventeen (81%) of 21 malignant cases and 11 (48%) of 23 benign cases had an N/C ratio of 0.50 or less. An N/C ratio of 0.50 or less had an odds ratio for malignancy of 4.64 (P = .03). A combined category of an N/C ratio of 0.50 or less and greater than 20 cell groups had an odds ratio for malignancy of 7.0 (P = .04). Establishing defined objective WSI criteria has the potential to provide an assessment of malignancy for AUS thyroid FNA cases.

Low malignancy risk of thyroid follicular lesion of undetermined significance in patients from post-endemic areas

OBJECTIVE

New classification of the thyroid fine-needle aspiration biopsy (FNAB) results tries to stratify the risk of malignancy of thyroid follicular lesions using 'follicular lesion of undetermined significance' (FLUS) subcategory. Clinical significance of this category in the endemic (or post-endemic) areas has not been clearly established.

DESIGN

The aim of the study was to determine the risk of malignancy for FLUS as well as to evaluate ultrasound (US) malignancy risk features (MRF) in such nodules in comparison with 'suspicious for neoplasm' (SFN) and 'benign lesions' (BL).

METHODS

The US images and cytological diagnoses of 589 thyroid follicular lesions were analysed from January 2010 to July 2012. Cytological follow-up was assessed in 110 cases and surgical one in 100 cases.

RESULTS

FLUS was diagnosed in 340 cases (3.8% of all cytological diagnoses and 57% of thyroid follicular lesions). Altogether, clinical and/or surgical follow-up revealed thyroid cancer in 3.2% patients with FLUS nodules. Repeat FNAB led to more specific diagnosis in 74.4% of FLUS (3.5%, papillary cancers or their suspicion; 2.3%, SFN; 68.6%, BL). The histopathological examination showed thyroid cancer in 6.4% cases of FLUS and 7.0% of SFN and follicular adenoma in 8.5% of FLUS and 11.6% of SFN (NS, FLUS vs SFN). FLUS showed MRF of intermediate values between BL and SFN; SFN more often than FLUS showed at least two MRF (53 vs 30%, P<0.0001).

CONCLUSIONS

The risk of cancer in FLUS in areas with recently corrected iodine supply is low. In such areas, repeated biopsy leads to more precise cytological diagnosis in about 3/4 cases.

Fine needle aspiration cytology of thyroid follicular neoplasm: cytohistologic correlation and accuracy

BACKGROUND

This study evaluated the accuracy of fine needle aspiration cytology (FNAC) in cases of follicular neoplasm (FN) on the basis of histologic diagnosis, and reviewed the cytologic findings of FN according to the FNAC.

METHODS

Among the 66 cases diagnosed with thyroid FN by FNAC during the 7-year period from 2003 to 2009, 36 cases that had undergone thyroid surgery were available for review. Cytologic diagnosis was compared with the histologic diagnosis of each case.

RESULTS

Among the 36 cases with a cytologic diagnosis of thyroid FN, histologic diagnosis was as follows: 20 follicular adenomas (55.6%), 3 Hurthle cell adenomas (8.3%), 2 follicular carcinomas (5.6%), 8 nodular goiters (22.2%), 2 papillary carcinomas (5.6%), and 1 Hashimoto's thyroiditis (2.8%), resulting in a diagnostic accuracy of FNAC for thyroid FN of 69.5%.

CONCLUSIONS

This study shows that FNAC for thyroid FN is a useful primary screening method because when FN is diagnosed by FNAC, the rate of FN histologic diagnosis is relatively high, however, adequate sampling and experience is a prerequisite for this procedure.

[Bethesda classification of fine needle punctures of the thyroid. Much ado about nothing really new?]

The Bethesda system for reporting thyroid cytopathology was published in 2008 (Baloch et al. 2008, Cytojournal 5:6; Baloch et al. 2008, Diagn Cytopathol 36:425-437) offering a classification system which is closely related to clinical data. The aim was to ensure adequate terminology without risk of errors in understanding, to advise clinicians concerning therapeutic options in relationship to cytological diagnoses as well as to facilitate the comparison of cytology data at national and international levels. However, mainly due to specific US American (both medical and legal) demands, this classification system is not yet fully appreciated in most European countries. The reasons are various: (a) Criteria for representative material are much more restrictive than those commonly used and in Germany a higher number of (unnecessary) repunctures would be the consequence. (b) It remains doubtful whether the introduction of a new and rather heterogeneous category of "atypia of undetermined significance or follicular lesion of undetermined significance" would contribute to a substantial decrease of findings classified as "follicular neoplasia". Furthermore it is unlikely that clinicians would be willing to accept the recommended conservative approach with repuncture if a new diagnostic category is associated with a calculated risk of malignancy in 5-15% cases. (c) Until now an integration of new developments in molecular markers into the Bethesda system is missing. Thus, for experienced cytologists the Bethesda system for reporting thyroid cytopathology offers very limited benefits in comparison to the currently used, established and highly accepted classification systems. However, a positive argument remains the fact that an internationally accepted classification system may improve the comparability of the results of national and international studies on thyroid findings.

Analysis of the bethesda system for reporting thyroid cytopathology and similar precursor thyroid cytopathology reporting schemes

The Bethesda System for Reporting Thyroid Cytopathology is a standardized reporting system for classifying thyroid fine-needle aspiration results comprising of 6 diagnostic categories with unique risks of malignancy and recommendations for clinical management. The majority of thyroid nodules are benign; however, up to 30% of fine-needle aspiration of thyroid nodule results are equivocal. Until 2007, various diagnostic terms were used to classify such cases, including "atypical," "indeterminate," and rule-out or cannot exclude malignancy. A literature review of 13 original studies was conducted to evaluate whether utilization of the Bethesda System for Reporting Thyroid Cytopathology nomenclature represent an improvement over thyroid cytopathology reporting schemes used before 2007 in diagnosing thyroid malignancy. The sensitivity and specificity of thyroid fine-needle aspiration was high in the studies that assessed the measures. However, a selection bias exists and most studies do not include indeterminate diagnosis in their calculations. Although the Bethesda System for Reporting Thyroid Cytopathology recommends a repeat fine-needle aspiration to follow-up nondiagnostic specimens, in the majority of studies, an appreciable number of cases underwent follow-up surgical biopsy or thyroidectomy. The diagnostic category of atypia/follicular lesion of undetermined significance remains heterogenous in terms of usage and clinical outcome. The majority of the studies that utilize the Bethesda System for Reporting Thyroid Cytopathology in this literature review retrospectively reclassified thyroid fine-needle aspiration into the Bethesda System for Reporting Thyroid Cytopathology nomenclature with reported malignancy rates that are similar between cases reclassified as atypia/follicular lesion of undetermined significance and follicular neoplasm/suspicious for follicular neoplasm.