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

Improved diagnostic accuracy of thyroid fine-needle aspiration cytology with artificial intelligence technology

BACKGROUND

Artificial intelligence (AI) is increasingly being applied in pathology and cytology, showing promising results. We collected a large dataset of whole slide image of thyroid fine needle aspiration cytology (FNA), incorporating z-stacking, from institutions across the nation to develop an AI model.

METHODS

We conducted a multi-center retrospective diagnostic accuracy study using thyroid FNA dataset from the Open AI Dataset Project that consists of digitalized images samples collected from three university hospitals and 215 Korean institutions through extensive quality check during the case selection, scanning, labeling, and reviewing process. Multiple z-layer images were captured using three different scanners and image patches were extracted from whole slide images and resized after focus-fusion and color normalization. We pre-tested six AI models, determining Inception ResNet v2 as the best model using a subset of dataset, and subsequently tested the final model with total datasets. Additionally, we compared the performance of AI and cytopathologists using randomly selected 1,031 image patches and reevaluated the cytopathologists' performance after reference to AI results.

RESULTS

A total of 10,332 image patches from 306 thyroid FNAs, comprising 78 malignant (Papillary thyroid carcinoma) and 228 benign from 86 institutions were used for the AI training. Inception ResNet v2 achieved highest accuracy of 99.7%, 97.7%, and 94.9% for training, validation, and test dataset, respectively (Sensitivity 99.9%, 99.6%, and 100% and specificity 99.6%, 96.4%, and 90.4% for training, validation, and test dataset, respectively). In the comparison between AI and human, AI model showed higher accuracy and specificity than the average expert cytopathologists beyond the two-standard deviation (Accuracy 99.71% (95% CI, 99.38-100.00%) vs. 88.91% (95% CI, 86.99-90.83%), sensitivity 99.81% (95% CI, 99.54-100.00% ) vs. 87.26% (95% CI, 85.22-89.30%), and specificity 99.61% (95% CI, 99.23-99.99%) vs. 90.58% (95% CI, 88.80-92.36%). Moreover, after referring to the AI results, all the performance of the experts increased (Accuracy 96%, 95%, and 96%, respectively) as well as diagnostic agreement (from 0.64 to 0.84).

CONCLUSIONS

These results suggest that the application of AI technology to thyroid FNA cytology may improve the diagnostic accuracy as well as intra- and inter-observer variability among pathologists. Further confirmatory research is needed.

Malignancy rates in thyroid nodules: a long-term cohort study of 17,592 patients

Objectives

Ultrasound diagnosis of thyroid nodules has greatly increased their detection rate. Their risk for malignancy is estimated between 7 and 15% in data from specialized centers which are used for guidelines recommendations. This high rate causes considerable anxiety to patients upon first diagnosis. Here, we retrospectively analyzed the malignancy rate of sonographically diagnosed nodules larger than 1 cm from a primary/secondary care center when long-term longitudinal follow-up was included.

Patients/methods

In the study, 17,592 patients were diagnosed with a thyroid nodule larger than 1 cm, of whom 7776 were assessed by fine-needle aspiration cytology (FNAC) and 9816 by sonography alone. 9568 patients were initially discharged due to innocent results of FNAC and/or ultrasound. In 1904 patients, definitive histology was obtained, and 6731 cases were included in the long-term follow-up (up to 23 years, median 5 years).

Results

Malignancy was histologically confirmed in 189 patients (1.1% of all) when excluding accidentally diagnosed papillary microcarcinomas. 155 were diagnosed during the first year of management, 25 in years 2-5 of follow-up, 9 in years 6-10 and nil in 1165 patients followed beyond 10 years.

Conclusions

The malignancy rate of thyroid nodules from primary/secondary care was much lower than that previously reported. During follow-up for more than 5 years, their rate rapidly dropped to less than 1/1000 cases. This low malignancy rate may help to reassure patients first confronted with the diagnosis of a thyroid nodule, substantially reduce their anxiety and avoid unwarranted diagnostic and therapeutic procedures.

CD56 Expression in Papillary Thyroid Carcinoma Is Highly Dependent on the Histologic Subtype: A Potential Diagnostic Pitfall

Loss of CD56 expression has been regarded as a diagnostic marker of papillary thyroid carcinoma (PTC). However, certain variants of PTC can aberrantly express CD56. Using a digital image analysis tool, we evaluated H-scores of CD56 immunostaining in 216 thyroid tumors. The H-score of the CD56 of all PTCs was lower than that of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) (P<0.001). The H-scores of CD56 were lower in classic PTC, the infiltrative follicular variant, and the diffuse sclerosing variant than in other PTC variants (P<0.001), whereas the H-scores were higher in tall cell variant, Warthin-like variant, and cribriform-morular variant than in classic PTC (P<0.001). The optimal cutoff value of H-scores for the CD56 expression was 180 for differentiating the NIFTP from the follicular adenoma and 30 for the differential diagnosis of NIFTP and infiltrative follicular variant PTC. CD56 expression is predominantly lost in classic and infiltrative follicular variants of PTCs and more preserved in the other histologic subtypes of PTC and NIFTP. CD56 is particularly useful for differentiating PTC from follicular-pattern thyroid neoplasms, but the aberrant expression in uncommon variants of PTC could be a diagnostic pitfall.

Risk stratification of indeterminate thyroid nodules by novel multigene testing: a study of Asians with a high risk of malignancy

Molecular testing of indeterminate thyroid nodules informs about the presence of point mutations, insertions/deletions, copy number variants, RNA fusions, transcript alterations and miRNA expression. American Thyroid Association (ATA) guidelines suggest molecular testing of indeterminate thyroid nodules may be considered to supplement risk of malignancy (ROM). Although these recommendations have been incorporated in clinical practices in the US, molecular testing of indeterminate thyroid nodules isn't common practice in Asia. Here, we performed molecular testing of 140 indeterminate nodules from Chinese patients using a novel molecular platform composed of RNA and DNA-RNA classifiers, which is similar to Afirma GEC and ThyroSeq v3. Compared with reports from North America, the new RNA and DNA-RNA classifiers had a higher positive predictive value (p1=0.000, p2=0.020) but a lower negative predictive value (p1=0.004, p2=0.098), with no significant differences in sensitivity (p1=0.625, p2=0.179) or specificity (p1=0.391, p2=0.264). Out of 58 resected nodules, 10 were borderline and 33 malignant, indicating a 74.1% ROM, which was higher than reports in North America (10-40% ROM). Our findings emphasize molecular testing with the newly-reported RNA and DNA-RNA classifiers can be used as a "rule-in" test when ROM is high.

Predictors of Malignancy in Thyroid Nodules Classified as Bethesda Category III

OBJECTIVE

To determine predictors of malignancy in surgically treated Bethesda category III nodules.

METHODS

Patients with surgically treated thyroid nodules classified as Bethesda category III were retrospectively enrolled. The association between clinical/sonographic features and postoperative pathology was evaluated using univariate and multivariate analyses.

RESULTS

A total of 188 nodules from 184 patients were included. The overall malignancy rate was 54.3%. In univariate analysis, male sex, aspect ratio >1, microcalcification, unclear boundary, BRAF^V600E mutation, and nuclear atypia were significantly associated with malignant disease in Bethesda category III nodules. Multivariate analysis confirmed that male sex, aspect ratio >1, microcalcification, and BRAF^V600E mutation were independent predictors of malignant disease.

CONCLUSIONS

Malignant disease was common in Bethesda category III nodules, and surgical treatment was strongly indicated in the presence of male sex, aspect ratio>1, microcalcification, and BRAF^V600E mutation.

Effect of the Noninvasive Follicular Thyroid Neoplasm With Papillary-Like Nuclear Features (NIFTP) Nomenclature Revision on Indian Thyroid Fine-Needle Aspiration Practice

OBJECTIVES

To analyze risk of malignancy (ROM) in Bethesda categories (BCs) and the impact of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) reclassification on malignancy risk and surgical outcome.

METHODS

In this retrospective study based on fine-needle aspiration samples with histologic follow-up, ROM was analyzed in BCs. Possible cases of NIFTP were reviewed, followed by the analysis of impact of this reclassification on ROM in BCs.

RESULTS

The incidence of NIFTP was 6.9% among excised thyroid nodules and 16.8% among all resected neoplastic lesions. ROM for BCs I to VI was 37.5%, 9.6%, 40.0%, 46.5%, 88.8%, and 96.8%, respectively. Risk of neoplasia was 50.0%, 13.8%, 55.0%, 71.2%, 88.8%, and 96.8% respectively. When NIFTPs were considered nonmalignant lesions, ROM decreased by 6.3%, 4.3%, 20%, 19.1%, 22.5%, and 1.5% in each Bethesda category (I-VI), respectively. Inability to diagnose NIFTP preoperatively led to overtreatment in 16.2%.

CONCLUSIONS

Prevalence of NIFTP in Asian countries may be higher than expected. Substantial cases of NIFTP have a benign preoperative cytology; hence, cases of follicular adenoma and adenomatous colloid nodule should be included in the review. NIFTP reclassification has significantly reduced the ROM in indeterminate BCs, suggesting diagnostic lobectomy rather than total thyroidectomy. Countries should establish their own malignancy risk range and parameters.

Subclassification of the Bethesda Category III (AUS/FLUS): A study of thyroid FNA cytology based on ThinPrep slides from the National Cancer Center in China

BACKGROUND

The atypia of an undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) category in the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) is a heterogeneous category, which includes various cell patterns. The subclassification of AUS/FLUS was suggested in the 2017 TBSRTC. However, the risk of malignancy (ROM) associated with different subgroups remains unresolved. Herein, AUS/FLUS aspirates were subclassified, from which the ROM of each subgroup was determined.

METHODS

All cases undergoing fine-needle aspiration (FNA) from July 2013 to December 2018 were reviewed. Of 12,913 thyroid FNAs, 1053 (8.2%) were AUS/FLUS. The slides of 222 patients with AUS/FLUS with surgical follow-up were reviewed and subclassified according to the recommendations of the 2017 TBSRTC. There were 195 aspirates consistently diagnosed as AUS/FLUS and subclassified as cytologic atypia 1 (AUS-C1); cytologic atypia 2 (AUS-C2); architectural atypia (AUS-A); cytologic and architectural atypia (AUS-C&A); Hürthle cell aspirates (AUS-H); atypia, not otherwise specified (AUS-NOS); and atypical lymphoid cells, rule out lymphoma (AUS-L).

RESULTS

Malignancy was identified in 83.3% (185 of 222) of the AUS/FLUS nodules. The AUS-C1 group was the most common (62.1%), followed by the AUS-C&A (12.8%), AUS-C2 (10.8%), AUS-H (6.7%), AUS-NOS (5.6%), AUS-L (1.5%), and AUS-A (0.5%) groups. AUS-C1 had the highest ROM (92.6%) among the groups and varied significantly from that of the AUS-C&A (P = .171), AUS-C2 (P = .001), AUS-H (P = .001), and AUS-NOS (P < .001) groups.

CONCLUSIONS

As a heterogeneous category of TBSRTC, the ROM for AUS/FLUS varies greatly among medical centers. Subclassification of AUS/FLUS might be helpful in identifying nodules with a high ROM in this category and improving the management of such nodules.

Preoperative diagnostic categories of fine needle aspiration cytology for histologically proven thyroid follicular adenoma and carcinoma, and Hurthle cell adenoma and carcinoma: Analysis of cause of under- or misdiagnoses

Cytologic diagnosis of thyroid follicular adenoma and carcinoma, and Hurthle cell adenoma and carcinoma (FACHAC) is challenging due to cytomorphologic features that overlap with other follicular-patterned lesions. This study was designed to analyze diagnostic categories (DCs) of preoperative fine needle aspiration cytology (FNAC) of histologically proven thyroid FACHACs to evaluate under- or misdiagnoses in FNAC and elucidate potential causes for such phenomena. A total of 104 thyroid nodules with preoperative FNAC which were diagnosed as FACHAC in resection specimens were included in this study. Of these, 66 cases had also undergone thyroid core needle biopsy (CNB); FNAC and CNB DCs were compared in these cases. Various cytologic and histologic parameters were compared between the nodules with different FNAC DCs. After a review of FNAC slides, DCs were re-assigned in 20 (19.2%) out of the 104 cases. Of the 66 cases with CNB diagnoses which were mostly classified as lower DCs in FNAC, 31 (47.0%) were diagnosed as suspicious for a follicular neoplasm in CNB. Cases which were underdiagnosed in FNACs were associated with lower cellularity, predominant macrofollicular pattern, absence of microfollicles arranged in trabecular pattern, and absence of transgressing vessels in cytology smears. High cellularity, microfollicles arranged in trabecular pattern, nucleolar prominence, and large cell dysplasia were more frequently found in malignancy than in benign neoplasm. In conclusion, thyroid FACHACs seem to be under- and misdiagnosed in preoperative FNAC. Innate characteristics of the nodules were associated with under-diagnosis as well as the quality of the FNAC specimens. Certain cytomorphologic features can be helpful in differentiating malignancy among FACHACs.

Indian experience of AUS/FLUS diagnosis: is it different from rest of Asia and the West?-A systematic review and meta-analysis

Background

Atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) is the most heterogeneous subcategory of the Bethesda system for thyroid cytopathology with laid down permissible limits of frequency and risk of malignancy (ROM). Due to differences in thyroid clinical practice worldwide, variations have been found in frequency, resection rates (RR) and ROM. Therefore, this systematic review and meta-analysis of AUS/FLUS across different regions was conducted and comparison of data from India was done with the rest of Asia and the West.

Methods

We searched PubMed and Google search engines from January 2009-Dec 2019 using terms "AUS Thyroid" and "FLUS Thyroid". Meta-analysis was performed using DerSimonian-Laird method and 95% confidence intervals were calculated using random effects model. Independent samples t-test was used to compare frequency, RR, and ROM of AUS/FLUS between India, rest of Asia and the West.

Results

Out of 15,000 studies on internet, 60 (18 Indian, 12 Asian and 30 Western) were included. Total aspirates were 201,657; 14,279 Indian, 62,448 Asian, 124,930 Western. Pooled estimates were: frequency 7.3% (6.3-8.3%), RR 41.9% (37.4-46.6%), ROM 33.3% (26.8-39.9%). Pooled prevalence of rate did not vary significantly across the three regions. Pooled prevalence of RR was highest in India (52.9%) and lowest in rest of Asia (26.5%); of ROM was highest in Asia (45.9%), lowest in the West (26.3%) (P<0.01). Statistical analysis demonstrated publication bias, limited to Indian and Western studies. Papillary thyroid carcinoma was the most common surgical diagnosis (87.9%; 1,082/1,231).

Conclusions

This meta-analysis showed differences in thyroid clinical practice followed in India, rest of Asia and the West. Although pooled prevalence of rate of AUS/FLUS was similar across the three, pooled RR and ROM varied. AUS/FLUS nodules were more frequently resected in Indian and Western studies than in rest of Asia. ROM was higher than recommended values in all three areas, being intermediate for India.

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

Background

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

Methods

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

Results

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

Conclusions

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

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

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

Thyroid cancer among patients with thyroid nodules in Yemen: a three-year retrospective study in a tertiary center and a specialty clinic

Background

The prevalence of thyroid cancer is increasing worldwide. No previous data are available on the prevalence of thyroid cancer in Yemen. We performed this study to determine the prevalence of thyroid cancer among patients with thyroid nodules in Yemen.

Methods

A retrospective chart review was performed for 550 patients with thyroid nodules who underwent fine needle aspiration and/or thyroid surgery at a private endocrine clinic and at an endocrine clinic in a tertiary hospital in Yemen over a 3 -year period from October 2016–2019. The prevalence of thyroid cancer; the sonographic findings, Bethesda classification, age, sex, thyroid stimulating hormone (TSH) levels of the patients; and the nodule size and number were reviewed.

Results

A total of 550 charts were reviewed [501 females (91.1%) and 49 males (8.9%)]. The thyroid cancer prevalence among the patients was 13.8% (CI = 10.9–16.7), and the mean age of the patients was 38.5 years (SD = 12.2). The TSH level and the rate of cancer were significantly related (P = 0.01), but no significant difference in the prevalence of thyroid cancer was found between females (13.4%) and males (18.4%) (P = 0.334). When correlating the rate of cancer with the ultrasound guided fine needle aspiration (UG-FNA) result, those with Bethesda system category III and IV, V and VI had malignancy rates of 20.8, 27.2, 52.4 and 69.2%, respectively. Thyroid nodules highly suspicious for malignancy on ultrasound had a 70% cancer diagnosis rate. The most common thyroid cancer was papillary cancer (71%), followed by follicular cancer (23.7%). Among those undergoing surgery, 44.2% had thyroid cancer, and 5.2% had a premalignant diagnosis.

Conclusion

Thyroid cancer has a higher prevalence in Yemen than in other middle eastern countries. Our study also reports a higher rate of follicular thyroid cancer than that in other published data, which has to be confirmed by further studies. The malignancy and premalignant diagnosis rate was ~ 50% in our patients who underwent surgery. Many centers in Yemen still do not perform FNA before thyroid surgery. It is important that other centers in the country start emphasizing the need for FNA before surgery. This will decrease the number of unnecessary surgeries and associated complications.

Comprehensive DNA Methylation Profiling Identifies Novel Diagnostic Biomarkers for Thyroid Cancer

Background: There are no reliable biomarkers to accurately differentiate indolent thyroid tumors from more aggressive thyroid cancers. This study aimed to develop new DNA methylation markers for diagnosis and recurrence risk stratification of papillary thyroid carcinoma (PTC). Methods: Thyroid tumor-specific DNA methylation profiling was investigated in 34 fresh frozen tissues, which included nontumor (n = 7), noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP, n = 6) and PTC (n = 21), using the Illumina HumanMethylation EPIC array. We performed a genome-wide assessment of thyroid tumor-specific differentially methylated CpG sites in the discovery set, then validated the top candidate markers in an independent set of 293 paraffin tissue samples comprised of follicular adenoma (FA, n = 61), Hürthle cell adenoma (HA, n = 24), NIFTP (n = 56), PTC (n = 120), follicular thyroid carcinoma (n = 27), and Hürthle cell carcinoma (n = 5), by pyrosequencing. Results: Three selected markers (cg10705422, cg17707274, and cg26849382) differentiated nonmalignant (FA, HA, and NIFTP) tumors from differentiated thyroid cancers with area under the receiver operating characteristic curve of 0.83, 0.83, and 0.80, respectively. Low DNA methylation levels for three markers were significantly associated with recurrent or persistent disease (odds ratio (OR) = 3.860 [95% confidence interval (CI) 1.194-12.475]) and distant metastasis (OR = 4.009 [CI 1.098-14.632]) in patients with differentiated thyroid cancer. A subgroup analysis for the validation set showed that PTC patients with low DNA methylation levels more frequently had aggressive histology, extrathyroidal extension, lymph node metastasis, BRAF^V600E mutations, and recurrent or persistent disease than those with high levels of methylation markers. All PTC patients who developed disease recurrence had low DNA methylation levels for three markers. Conclusions: DNA methylation levels of three markers can be useful for differentiating differentiated thyroid cancer from nonmalignant follicular thyroid lesions, and may serve as prognostic biomarkers for predicting recurrent or persistent disease after surgery for differentiated thyroid cancer.

Differences in surgical resection rate and risk of malignancy in thyroid cytopathology practice between Western and Asian countries: A systematic review and meta-analysis

There is increasing evidence showing that clinicians employ different management strategies in their use of The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC). In this meta-analysis, we investigated the differences in diagnosis frequency, resection rate (RR), and risk of malignancy (ROM) between Western (ie, American and European) and Asian cytopathology practices. We searched PubMed and Web of Science from January 2010 to January 2019. Proportion and 95% CIs were calculated using a random-effect model. We used independent sample t tests to compare frequencies, RR, and ROM between Western and Asian practices. We analyzed a total of 38 studies with 145,066 fine-needle aspirations. Compared with Asian practice, Western series had a significantly lower ROM in most of TBSRTC categories, whereas the RR was not statistically different. Focusing on indeterminate nodules, the RR in Western series was significantly higher (51.3% vs 37.6%; P = .048), whereas the ROM was significantly lower (25.4% vs 41.9%; P = .002) compared with those in Asian series. The addition of Asian cohorts increased ROM for most of diagnostic categories compared with the original TBSRTC. In conclusion, this study demonstrates a difference in Western and Asian thyroid cytology practice, especially regarding the indeterminate categories. Lower RR and higher ROM suggest that Asian clinicians adopt a more conservative approach, whereas immediate diagnostic surgery is favored in Western practice for indeterminate nodules. The addition of Asian series into a meta-analysis of TBSRTC altered ROM for several categories, which should be considered in future revisions of TBSRTC.

Comparison between ultrasonographic findings and fine needle aspiration cytology in differentiating malignant and benign thyroid nodules

The purpose of research was comparing the ultrasound (US) features and fine-needle aspiration cytology (FNAC) in detecting the thyroid nodules in clinical practice. A cross-sectional analytical study retrospectively reviewed the US and FNAC findings for a total of 170 thyroid nodules. The US features that we compared included echogenicity, calcifications, shape, halo and Doppler, between 2017 and 2018. Totally, 170 nodules of thyroid were studied, which contained 72 (42.4%) benign and 98 (57.6%) malignant thyroid nodules. The sonographic features were significantly associated with malignancy such as microcalcification (97.0%), hyperechogenicity (91.5%), wider than taller shape (98.0%), absent halo (90.9%) and positive Doppler (78.0%) (P < 0.01). The altogether accuracies of calcification, echogenicity, shape, halo, and Doppler were 0.96, 0.92, 0.97,0.82 and 0.82, respectively. Our data suggest that US features could be a good sonographic criterion for recommending FNA cytology with follow‐up thyroid sonography and FNA.

Nuclear features of papillary thyroid carcinoma: Comparison of Core needle biopsy and thyroidectomy specimens

BACKGROUND

Core needle biopsy (CNB) has been used as an alternative or a complementary method for diagnosis of thyroid nodules. However, morphological analysis of the nuclear features of papillary thyroid carcinoma (PTC) cells obtained via CNB remains unclear. Hence, we examined the differences between the PTC nuclear features in CNB and thyroidectomy specimens.

METHODS

Ten PTC patients, who underwent both CNB and thyroidectomy, were selected. Microscopic photographs of three representative areas of the PTC and adjacent parenchyma were taken. Ten cells per photograph were chosen, and 1200 cells were evaluated (300 PTC and 300 follicular cells in the CNB and thyroidectomy specimens, respectively). The area, circumference, major axis, and minor axis were measured using an image analyzer. Detailed nuclear features (size and shape, membrane irregularity, chromatin characteristics) were scored using a 3-point scale.

RESULTS

The mean nuclear area, circumference, major axis, and minor axis of PTC cells in the CNB specimen were 1.76, 1.34, 1.34, and 1.29 times larger than those of the follicular cells (p<0.001); similar results were seen in the thyroidectomy specimens (2.04, 1.41, 1.37, and 1.37: p<0.001). Comparative analysis revealed that these parameters were significantly smaller in the CNB specimens than those in the thyroidectomy specimens (p<0.001). Nuclear grades were also lower in the former owing to poor chromatin characteristics (clearing and margination) (p<0.01).

CONCLUSION

Considering that the PTC nuclei in CNB specimens are smaller with fewer irregularities and less clear than those in thyroidectomy specimens, we need to emphasize caution when using CNB specimens for diagnosis.

Current Status of Thyroid Fine-Needle Aspiration Practice in Thailand

Thyroid carcinoma is one of the leading malignancies in Thailand increasingly prevalent in the female population. Fine-needle aspiration (FNA) cytology is a widely used diagnostic tool for evaluation of thyroid nodules and thyroid cancer. Thyroid FNA is a routine procedure universally performed in Thai hospitals by a variety of clinical specialists. Manual guidance is the first-line choice complemented by ultrasound assistance in selected cases. Despite national guidelines recommendations, the diagnostic criteria and terminology of the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) was slowly adopted in the local settings. Currently, the Bethesda system is actively promoted by the local professional societies as a uniform reporting system. Experience with thyroid FNA has been rarely reported to date-only a handful of publications are available in local journals. Our review, in addition to presenting various aspects of thyroid FNA in Thailand, established for the first time national references for a certain statistical outputs of TBSRTC based on the original multi-institutional cohort. The risk of malignancy in 2,017 operated thyroid nodules collected from three tertiary thyroid cancer centers was 21.7%, 14.7%, 35.9%, 44.4%, 76.7%, and 92.6% for categories I to VI, respectively. The malignancy risk in several diagnostic categories (II to IV) was higher than the risk estimated by TBSRTC and recent meta-analysis studies. We endorse the use of uniform terminology of the Bethesda system in Thailand, which will help facilitate communication among diverse medical professionals involved in the management of patients with thyroid nodules, to share local experience with the international audience.

Thyroid Fine-Needle Aspiration Cytology Practice in Korea

We reviewed the current status of thyroid fine-needle aspiration cytology (FNAC) in Korea. Thyroid aspiration biopsy was first introduced in Korea in 1977. Currently, radiologists aspirate the thyroid nodule under the guidance of ultrasonography, and cytologic interpretation is only legally approved when a cytopathologist makes the diagnosis. In 2008, eight thyroid-related societies came together to form the Korean Thyroid Association. The Korean Society for Cytopathology and the endocrine pathology study group of the Korean Society for Pathologists have been updating the cytologic diagnostic guidelines. The Bethesda System for Reporting Thyroid Cytopathology was first introduced in 2009, and has been used by up to 94% of institutions by 2016. The average diagnosis rates are as follows for each category: I (12.4%), II (57.9%), III (10.4%), IV (2.9%), V (3.7%), and VI (12.7%). The malignancy rates in surgical cases are as follows for each category: I (28.7%), II (27.8%), III (50.6%), IV (52.3%), V (90.7%), and VI (100.0%). Liquid-based cytology has been used since 2010, and it was utilized by 68% of institutions in 2016. The categorization of thyroid lesions into "atypia of undetermined significance" or "follicular lesion of undetermined significance" is necessary to draw consensus in our society. Immunocytochemistry for galectin-3 and BRAF is used. Additionally, a molecular test for BRAF in thyroid FNACs is actively used. Core biopsies were performed in only 44% of institutions. Even the institutions that perform core biopsies only perform them for less than 3% of all FNACs. However, only 5% of institutions performed core biopsies up to three times more than FNAC.

Malignancy Rates of Thyroid Cytology: Cyst Fluid Benign or Non-Diagnostic?

Background

We sought to investigate subgroup distribution using Bethesda classification and risks for malignancy. We also compared the malignancy risk of cases that were denoted as non-diagnostic due to cystic contents, with cases that were denoted as non-diagnostic due to presence of other features.

Material/Methods

The study included pathology test results of 1,440 thyroid nodule samples diagnosed using Bethesda classification. Results of 305 thyroidectomy excision specimens from these patients were also compared with cytology results to determine the frequency of malignancy. The non-diagnostic group was divided into two categories: those with cystic contents, and others. Malignancy rates were separately calculated for the two groups, and compared with the other classification groups.

Results

Distribution of malignancy rates by Bethesda classification were as follows: non-diagnostic 12.5% (6/48), benign 1.5% (3/198), atypia of undetermined significance/follicular lesion of undetermined significance (AFLUS) 9% (1/11), suspicious for follicular neoplasm (SFN) 37.5% (3/8), suspicious malignancy 70% (8/26), malignancy 100% (14/14).

Conclusions

Despite the limited number of cases, our study concluded that cystic content was closer to the benign category than the non-diagnostic category if the assessment was based on malignancy rates. In this group, similar to aspirations containing plenty of lymphocytes that indicates colloid or lymphocytic thyroiditis, it is still controversial whether criterion for adequacy of follicular epithelial cells should be sought, or if they should be regarded as benign in order to prevent unnecessarily performance of repeat aspirations.