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

Welcoming the new, revisiting the old: a brief glance at cytopathology reporting systems for lung, pancreas, and thyroid

This review addresses new reporting systems for lung and pancreatobiliary cytopathology as well as the most recent edition of The Bethesda Reporting System for Thyroid Cytopathology. The review spans past, present, and future aspects within the context of the intricate interplay between traditional morphological assessments and cutting-edge molecular diagnostics. For lung and pancreas, the authors discuss the evolution of reporting systems, emphasizing the bridge between past directives and more recent collaborative efforts of the International Academy of Cytology and the World Health Organization in shaping universal reporting systems. The review offers a brief overview of the structure of these novel systems, highlighting their strengths and pinpointing areas that require further refinement. For thyroid, the authors primarily focus on the third edition of The Bethesda System for Reporting Thyroid Cytopathology, also considering the two preceding editions. This review serves as an invaluable resource for cytopathologists, offering a panoramic view of the evolving landscape of cytopathology reporting and pointing out the integrative role of the cytopathologist in an era of rapid diagnostic and therapeutic advancements.

The risk of malignancy in the atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) category subgroups: a Thai institute experience

INTRODUCTION

This study investigated the rate of reporting and the risk of malignancy (ROM) for atypia of undetermined significance (AUS) subgroups in a Thai population. AUS, which is category III of the Bethesda System for Reporting Thyroid Cytopathology, is a problematic diagnosis for thyroid nodule management because the risks of malignancy are diverse.

MATERIALS AND METHODS

Patients who underwent thyroid fine needle aspirations between January 2015 and December 2019 were included in this retrospective study. Gender, age, and nodule features were described, and all slides were re-evaluated and categorized into 2 subgroups: AUS-Nuclear (including cytology atypia and cytologic and architectural atypia) and AUS-Other (including architectural atypia, oncocytic atypia, and atypia not otherwise specified). The lower and upper limits of ROM were calculated for each subgroup.

RESULTS

Of total, 258 out of 2995 fine needle aspirations (8.6%) were diagnosed as AUS. The patients were predominantly female (88.9%), with a mean age of 54.1 years. The average nodule size was 2.5 cm. Of the 258 AUS patients, 81 (38.9%) had histological correlations. The ROM for the AUS category was 9.1% to 23.5%. The ROM of the AUS-Nuclear and AUS-Other were 11.1% to 27.3% and 2.2% to 6.7%, respectively. Features of pseudonuclear inclusions had the highest ROM (33.3%-42.9%), followed by pale chromatin (28.57%-47.06%).

CONCLUSIONS

Less than ten percent of our interpretations were AUS, which is acceptable in our practice. Cytological atypia harbored the highest ROM. Studies of associations between cytology and histology may aid in improving diagnostic criteria for this population.

The Asian Thyroid Working Group, from 2017 to 2023

The Asian Thyroid Working Group was founded in 2017 at the 12th Asia Oceania Thyroid Association (AOTA) Congress in Busan, Korea. This group activity aims to characterize Asian thyroid nodule practice and establish strict diagnostic criteria for thyroid carcinomas, a reporting system for thyroid fine needle aspiration cytology without the aid of gene panel tests, and new clinical guidelines appropriate to conservative Asian thyroid nodule practice based on scientific evidence obtained from Asian patient cohorts. Asian thyroid nodule practice is usually designed for patient-centered clinical practice, which is based on the Hippocratic Oath, "First do not harm patients," and an oriental filial piety "Do not harm one's own body because it is a precious gift from parents," which is remote from defensive medical practice in the West where physicians, including pathologists, suffer from severe malpractice climate. Furthermore, Asian practice emphasizes the importance of resource management in navigating the overdiagnosis of low-risk thyroid carcinomas. This article summarizes the Asian Thyroid Working Group activities in the past 7 years, from 2017 to 2023, highlighting the diversity of thyroid nodule practice between Asia and the West and the background reasons why Asian clinicians and pathologists modified Western systems significantly.

Interobserver variability in inconclusive diagnostic categories of thyroid fine needle aspiration cytology: An urban-based tertiary hospital experience

INTRODUCTION

Thyroid nodules are typical lesions, usually non-malignant, and surgery is unnecessary in most patients. However, distinguishing between benign and malignant is challenging. Fine needle aspiration cytology (FNAC) is considered a primary diagnostic and prognostic tool with an effective cost for evaluating thyroid enlargement. Unfortunately, using FNAC to diagnose inconclusive lesions in the category III-Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance (AUS/FLUS) based on TBSRTC classification is a problematic issue. This study aimed to evaluate the interobserver variability of AUS/FLUS interpretation among pathologists.

METHODS

A retro-observational study: previous 127 AUS/FLUS cases were enrolled. Seventy-two cases met inclusion criteria and were then reclassified by different anatomical pathologists under blinded-design assignments. The concordance among pathologists and the percent alteration of the risk of malignancy (ROM) were compared to the original reports and histological diagnosis.

RESULTS

About 72 % of AUS/FLUS cases were changed after the reclassification. Approximately 46 % were changed to benign while 12.5 % were reclassified as carcinoma. Moreover, 30 % of those original AUS/FLUS were histologically diagnosed as malignant or carcinoma lesions. The concordances among consensus diagnosis and results from each pathologist are acceptable, Kappa(s) were 0.674 to 0.898 (p < 0.001) and Spearman correlations were 0.820 to 0.957 (p < 0.0001).

CONCLUSION

There are substantial interobserver differences and changes in cytological diagnosis when re-evaluation is performed by multiple pathologists using TBSRTC. A second or third opinion should be sought routinely to establish a consensus diagnosis as a supplement to the initial diagnosis of AUS/FLUS. The reclassification reduces medical expenses and the rate of unnecessary surgery, especially in patients with cytologically confirmed benign thyroid nodules. Preoperative molecular evaluation is a promising method for assisting in the diagnosis of thyroid nodules, but additional research is necessary.

Molecular Testing for Thyroid Nodules: The Experience at McGill University Teaching Hospitals in Canada

In the past few decades, molecular characterization of thyroid cancer has made significant progress and is able to identify thyroid-cancer-related molecular markers that can then be applied clinically for improved decision making. The aim of this review is to provide a general overview about the molecular markers (mutations and alterations) of thyroid cancers, present several molecular tests, and discuss the clinical applications of identifying these markers supported by the clinical experience of several high-volume thyroid cancer specialists at the McGill university hospitals in Montreal, Canada. Our group experience showed that molecular testing can reclassify more than half of the patients with indeterminate thyroid nodules (Bethesda III and IV) into benign and spare these patients from unnecessary diagnostic surgery. Furthermore, it can help optimize the initial management in thyroid cancers with no evidence of high risk of recurrence of disease preoperatively. While routine molecular testing is not firmly established for thyroid FNA specimens that are suspicious or positive for malignancy (Bethesda V and VI), knowledge of a thyroid nodule’s molecular risk group profile in such cases, together with its clinical and radiologic features, can help select the optimal surgical options (lobectomy versus upfront total thyroidectomy and central neck dissection), as demonstrated by our studies.

Multi-institutional validation of a modified scheme for subcategorizing salivary gland neoplasm of uncertain malignant potential (SUMP)

BACKGROUND

The salivary gland neoplasm of uncertain malignant potential (SUMP) category in the Milan System is diagnostically challenging. This study aims to validate a modified scheme for subcategorizing SUMP in a large multi-institutional cohort.

METHODS

Retrospective review of salivary gland fine-needle aspirations (FNAs) from 10 institutions were classified based on the Milan System. Cases diagnosed as SUMP with available cytology slides and surgical follow-up were retrieved for review and subcategorized based on a modified scheme as follows: basaloid SUMP (B1: absent/scant nonfibrillary matrix; B2: presence of nonfibrillary/mixed-type matrix), oncocytic/oncocytoid SUMP (O1: with mucinous background; O2: without mucinous background), and SUMP not otherwise specified (NOS).

RESULTS

A total of 742 (7.5%) cases from 9938 consecutive salivary gland FNAs were classified as SUMP. Among them, 525 (70.8%) had surgical follow-up and 329 (62.7%) were available for review. The overall risk of malignancy (ROM) of SUMP was 40.4%. There were 156 cases (47.4%) subcategorized as basaloid SUMP with a ROM of 36.5%, 101 (30.7%) as oncocytic/oncocytoid SUMP with a ROM of 52.5%, and 72 (21.9%) as SUMP NOS with a ROM of 31.9%. The ROM of oncocytic/oncocytoid SUMP was significantly higher than basaloid SUMP (P = .0142) and SUMP NOS (P = .0084). No significant differences in ROM were noted between B1 and B2 (36.7% vs 36.4%, P = 1.0000) and O1 and O2 (65.2% vs 48.7%, P = .2349).

CONCLUSIONS

The ROM of oncocytic/oncocytoid SUMP was 52.5% and significantly higher than that of basaloid SUMP (36.5%, P = .0142) and SUMP NOS (31.9%, P = .0084), whereas no significant differences in ROM were noted for cases with different types of extracellular matrix or background material.

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.

The predictive value of hematologic parameters in the risk of thyroid malignancy in cases with atypia/follicular lesion of undetermined significance

BACKGROUND

Atypia/follicular lesion of undetermined significance (AUS/FLUS) is still the most challenging category in the Bethesda System for Reporting Thyroid Cytopathology. Therefore, the aim of the current study was to investigate the value of the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and mean platelet volume (MPV) in predicting malignancy in cases with AUS/FLUS nodules.

METHODS

A total of 200 patients with AUS/FLUS nodules who underwent thyroidectomy were included in this study. Preoperative hemogram parameters, ultrasonographic findings, fine-needle aspiration results, and postoperative final histopathological diagnoses of the patients were recorded retrospectively.

RESULTS

Thyroid malignancies were detected in 122 of the patients (61.0%). Patients in the benign group (BG) were older than those in the malignancy group (MG) (52.0 ± 11.3 vs. 45.9 ± 12.3 years, p  < 0.001). The median TSH values of the two groups were comparable. Statistically significant differences were obtained between the two groups in respect of mean WBC of 7.53 ± 1.44 in MG and 6.87 ± 1.35 (10³/mm³) in BG, mean neutrophil of 4.65 ± 1.12 in MG and 3.95 ± 0.99 (10³/mm³) in BG, and median NLR of 2.18 (0.71-4.57) in MG and 1.75 (0.80-3.42) in BG (p  < 0.001). The median PLR and MPV values of the two groups were similar. When NLR cut-off point was designated as 2.24, the accuracy of NLR in distinguishing malignancy from the benign condition was 0.65 in ROC analysis (area under the curve, 0.665; specificity, 0.808; sensitivity, 0.492).

CONCLUSION

High NLR values may provide limited help in predicting thyroid malignancy in the AUS/FLUS nodule population, while PLR and MPV are not reliable parameters.

The Risk Stratification of Papillary Thyroid Cancer With Bethesda Category III (Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance) by Thyroid Fine-Needle Aspiration Could Be Assisted by Tumor Size for Precision Treatment

PURPOSE

To investigate the clinical characteristics of papillary thyroid cancer (PTC) classified as Bethesda category III [atypia of undetermined significance (AUS)/follicular lesion of undetermined significance (FLUS)] by fine-needle aspiration (FNA) for precision treatment.

METHODS

A total of 1,739 patients diagnosed with Bethesda category III (AUS/FLUS) by FNA were investigated, and 290 patients diagnosed with PTC were analyzed.

RESULTS

The rate of papillary thyroid microcarcinoma (PTMC) was 82.1% (238/290). The rates of lymph node metastases were 44.9% (22/49) and 25.2% (56/222) for PTC and PTMC, respectively (p = 0.006). The rates of extra-thyroid extension were 46.2% (24/52) and 19.8% (47/237) (p < 0.001). Compared with PTMC, PTC had significantly higher odds ratios (ORs) of 3.41 (1.81-6.44, p < 0.001), 2.19 (1.16-4.13, p = 0.016), and 2.51 (1.29-4.88, p = 0.007) for extra-thyroid extension, multifocality, and lymph node metastases, respectively, after adjustment for age and gender. The larger size and BRAF V600E mutation had a robust synergistic effect for invasive features. The rates of lymph node metastases, multifocality, and extra-thyroid extension were significantly increased with larger sizes harboring BRAF V600E mutation. Compared with PTMC harboring wild type (WT)-BRAF, PTC harboring BRAF V600E mutation had adjusted higher ORs of 3.01 (1.26-8.68, p = 0.015), 3.20 (1.22-8.42, p = 0.018), and 5.62 (2.25-14.01, p < 0.001) for lymph node metastases, multifocality, and extra-thyroid extension, respectively.

CONCLUSIONS

In this study, risk stratification was recommended for patients with Bethesda category III (AUS/FLUS) nodules with a size under 1 cm harboring WT-BRAF being regarded as low risk and should be recommended for active surveillance. Nodules with a size over 1 cm harboring WT-BRAF or those under 1 cm harboring BRAF V600E mutation could be regarded as moderate risk, and molecular testing should be recommended. However, those with a size over 1 cm harboring BRAF V600E mutation should be regarded as high risk, and a diagnostic surgery should be recommended.

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.

Comparison of Korean vs. American Thyroid Imaging Reporting and Data System in Malignancy Risk Assessment of Indeterminate Thyroid Nodules

BACKGROUND

The management of cytologically indeterminate thyroid nodules is challenging for clinicians. This study aimed to compare the diagnostic performance of the Korean Thyroid Imaging Reporting and Data Systems (K-TIRADS) with that of the American College of Radiology (ACR)-TIRADS for predicting the malignancy risk of indeterminate thyroid nodules.

METHODS

Thyroid nodules diagnosed by fine-needle aspiration (FNA) followed by surgery or core needle biopsy at a single referral hospital were enrolled.

RESULTS

Among 200 thyroid nodules, 78 (39.0%) nodules were classified as indeterminate by FNA (Bethesda category III, IV, and V), and 114 (57.0%) nodules were finally diagnosed as malignancy by surgery or core needle biopsy. The area under the curve (AUC) was higher for FNA than for either TIRADS system in all nodules, while all three methods showed similar AUCs for indeterminate nodules. However, for Bethesda category III nodules, applying K-TIRADS 5 significantly increased the risk of malignancy compared to a cytological examination alone (50.0% vs. 26.5%, P=0.028), whereas applying ACR-TIRADS did not lead to a change.

CONCLUSION

K-TIRADS and ACR-TIRADS showed similar diagnostic performance in assessing indeterminate thyroid nodules, and K-TIRADS had beneficial effects for malignancy prediction in Bethesda category III nodules.