Diagnostic Frequency Ratios Are Insufficient to Measure Laboratory Precision with The Bethesda System for Reporting Thyroid Cytopathology

Thyroid fine-needle aspiration cytology: malignancy rate in the category of indeterminate significant atypia/indeterminate significant follicular lesion

BACKGROUND

Fine needle aspiration cytology (FNAC) is a standard preoperative diagnostic modality for thyroid nodules. The Bethesda Thyroid Cytopathology Reporting System (TBSRTC) defines the FNAC atypia group as atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS).

OBJECTIVES

Determine the risk of malignancy after surgical resection in patients with AUS/FLUS.

DESIGN

Retrospective.

SETTING

Pathology department of a tertiary care center.

PATIENTS AND METHODS

All thyroid FNACs between 2015 and 2023 that were diagnosed as AUS/FLUS in Turkey. Patient demographics, preoperative ultrasonographic features, and follow-up data were collected.

MAIN OUTCOME MEASURES

Relationship between AUS/FLUS diagnosis and final histopathological diagnosis.

SAMPLE SIZE

562.

RESULTS

In total, 562 thyroid nodules were diagnosed as AUS/FLUS, and 267 (47.5%) were surgically excised. A malignant histopathological diagnosis was given in 28 cases (10.4%). Malignancy risk sensitivity of AUS/FLUS diagnosis was 75.68% (95% CI=58.80-88.23%), specificity was 55.24% (95% CI=50.91-59.52%), positive predictive value was 10.49% (95% CI=8.71-12.58%), and negative predictive value was 97.04% (95% CI=94.86-98.31%). In the ultrasonographic data, having symptomatic nodules, nodule calcification, and irregular nodule borders were all statistically significant signs of cancer in a one-variable analysis (P<.01). The presence of a family history emerged as a statistically significant prognostic marker for malignancy (P=.012). Although not statistically significant, the malignancy rate for nodules with nuclear atypia was 11.9%, significantly higher than the rate of 8.3% for nodules with architectural atypia only (P=0.32).

CONCLUSIONS

The diagnosis of AUS/FLUS has a high rate of predicting the risk of malignancy and should continue to be offered. In addition to cytopathological features, ultrasound data and family history should be taken into consideration when evaluating the case.

LIMITATIONS

Retrospective design and no molecular studies.

Accuracy of Thyroid Fine-Needle Aspiration Cytology: A Cyto-Histologic Correlation Study in an Integrated Canadian Health Care Region with Centralized Pathology Service

INTRODUCTION

The reported ROM within TBSRTC categories varies widely and depends on several factors in the clinical care pathway for thyroid nodules, including sonographic risk stratification, cytology expertise, selection criteria for surgical resection, and definitions of malignancy used.

METHODS

We present 5,867 consecutive thyroid FNAC and corresponding surgical pathology in the context of a comprehensive, single-payer health care system with centralized cytology and surgical pathology services for over 1.5 million inhabitants.

RESULTS

We report higher usage of ND and AUS/FLUS categories than the literature (19% vs. <10% and 15% vs. <10%, respectively). Our surgical resection rate for malignant cytology is substantially higher than the literature (94% vs. 50%, respectively). The ROM by the TBSRTC category in our cohort was similar to the literature. The overall diagnostic accuracy of thyroid FNAC was 92%, which is similar to other studies. Inclusion of incidental PMC as histologically malignant raised the ROM in the ND, benign, and AUS/FLUS categories.

DISCUSSION

The diagnostic performance of thyroid FNAC in our study is similar to the reported literature. Differences in TBSRTC category usage likely arise from cytologist variability and expertise. Our higher surgical resection rate in the malignant cytology category reflects the greater capture of surgical follow-up within our healthcare region with centralized pathology and a single EMR system. Keeping in mind the method of calculation of ROM, the malignancy rate by TBSRTC is similar to previous reports.

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

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

Atypia of Undetermined Significance in Thyroid Fine-Needle Aspirations: Follow-Up and Outcome Experience in Newfoundland, Canada

INTRODUCTION

The rates of atypia of undetermined significance (AUS) by fine-needle aspiration (FNA) and malignant outcomes have been estimated at < 7% and 5-15%, respectively. Initial AUS diagnosis is followed up clinically with serial ultrasounds, repeat FNA, molecular testing, or direct surgery. We investigated the incidence, follow-up modalities, and final outcomes of AUS in Newfoundland.

METHODS

All cases of AUS diagnosed at the Eastern Health Cytology Laboratory between 1 January 2010 and 31 December 2013 were identified. Electronic medical records were examined for follow-up modalities and final histologic diagnosis. The final outcomes were reported as benign, malignant, or undetermined.

RESULTS

Out of 3,285 thyroid FNAs, 181 (5.5%) were AUS. Fifty-seven (31.5%) had repeat FNA diagnosed as benign (38.6%), AUS (29.8%), or suspicious/malignant (8.8%). Eighty-four (46.4%) had surgery after the first AUS diagnosis, 39 (46.4%) of which were malignant. Twenty-four patients (13.3%) were followed up by serial ultrasound only, 2 (1.1%) by molecular testing, and 1 (0.6%) died of unrelated disease. Thirteen (7.2%) had no follow-up record. Our malignancy rate (MR) was 29.8%.

CONCLUSION

The MR in our population was higher than the rate proposed by The Bethesda System for Reporting Thyroid Cytopathology. Repeat FNA can reduce the rate of unnecessary surgeries, but practice guidelines should consider individual and institutional circumstances. The ratio MR:ADR (AUS diagnostic rate) may be a better indicator of performance.

Reproducibility of "The Bethesda System for Reporting Thyroid Cytopathology:" A Retrospective Analysis of 107 Patients

Objectives:

Fine-needle aspiration cytology (FNAC) has emerged as an indispensable tool to discriminate thyroid lesions into benign or malignant for appropriate management. The need for simplicity of communication and standardization of terminology for thyroid FNAC reporting led to introduction of “The Bethesda system for reporting Thyroid Cytopathology” (TBSRTC) in a conference held at the National Cancer Institute in 2007. This study aims at establishing the reproducibility of TBSRTC for diagnosing thyroid lesions.

Materials and Methods:

The present study comprised thyroid FNAC from 107 patients retrospectively over a period of 1.5 year (June 2013 to December 2014), which were reviewed by two trained cytopathologists and re-categorized according to TBSRTC. The interobserver variation and reproducibility of the reporting system was statistically assessed using Cohen's kappa.

Results:

The cytopathologists were in agreement in 98 out of 107 cases (91.5%). Maximum concordance was noted in benign category (91 of 96 cases; 92.85%), followed by 2 cases each in nondiagnostic/unsatisfactory (ND/US) and follicular neoplasm/suspicious for follicular neoplasm (FN/SFN) category (2.04% each) and 1 case each in atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS), suspicious for malignancy (SUS), and malignant category (1.02% each). The highest diagnostic disagreement was noted among ND/US and benign and benign and FN/SFN categories.

Conclusion:

The utilization of TBSRTC for reporting thyroid cytology should be promoted in our country because it provides a homogeneous, standardized, and unanimous terminology for cytological diagnosis of thyroid lesions. The present study could substantiate the diagnostic reproducibility of this system.

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.

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.

Cytotechnologist Performance for Screening Hürthle Cell Atypia in Indeterminate Thyroid Fine-Needle Aspirates

OBJECTIVES

We have previously shown that specimens diagnosed as containing Hürthle cells have a 12% chance of being malignant if they are classified as atypia of undetermined significance (AUS-HC). The identification of Hürthle cells by cytotechnologists (CTs) during screening can improve cytopathologist efficiency and may prevent diagnostic errors due to the oversights of focal findings. Here, we examine the performance of our institutional CTs when screening for Hürthle cell atypia in thyroid fine-needle aspiration (FNA) specimens.

STUDY DESIGN

Information on 8,814 thyroid cytopathology specimens was retrieved for a 10-year period. Specimens were screened by 1 of 11 CTs. A subsample of cases was categorized either as AUS-HC or suspicious for Hürthle cell neoplasm.

RESULTS

AUS-HC screening diagnoses were more likely to be downgraded to benign but less likely to be upgraded compared to AUS diagnoses with nuclear or microfollicular atypia. AUS-HC represents almost all papillary thyroid carcinoma (PTC) screening diagnoses downgraded to the AUS category, which suggests that even low levels of Hürthle cell atypia can result in PTC being included in the differential diagnosis.

CONCLUSION

Overall, there are few major discrepancies between CT and pathologist diagnoses for specimens containing Hürthle cell atypia.