Cell block is a valuable adjunct to conventional smear for thyroid fine needle aspiration: 2395 cases with histological correlation

Diagnostic Value and Challenges of BRAF V600E Molecular Testing and Thyroid Fine-Needle Aspiration Cytology: A Retrospective Study from a Tertiary Institution in Southern Hunan Province, China

INTRODUCTION

Combined thyroid fine-needle aspiration (FNA) cytology and valine-to-glutamate substitution at codon 600 of B-Raf proto-oncogene, serine/threonine kinase (BRAF V600E) mutation detection are procedures used for diagnosing thyroid nodules in many Chinese tertiary institutions. This retrospective study at our institution aimed to explore the effectiveness and challenges of the combined approach in diagnosing thyroid nodules and the correlation between BRAF V600E mutation status and behavior of papillary thyroid carcinoma.

METHODS

Thyroid FNA cytology and BRAF V600E mutation detection results were reviewed between November 2020 and July 2022. A total of 623 patients, each of whom underwent thyroidectomy and final pathological examination after FNA cytology diagnosis, were included in the study. The relationship between the BRAF V600E mutational status and pathological parameters was analyzed using the χ2 test. The effectiveness and challenges of FNA cytology alone and the combined procedure were also evaluated based on the final pathology.

RESULTS

Of 623 patients, 591 were diagnosed with papillary thyroid carcinoma (PTC), of which 456 were positive for the BRAF V600E mutation. It demonstrated near-perfect specificity for identifying PTC, and its incidence rate showed an age-specific curve with an inverted U-shaped distribution. The final pathological examination showed that the combined procedure had a higher sensitivity (83.91%) than FNA cytology alone (63.45%) for distinguishing PTC from other lesions (p < 0.001). Mutational status was associated with a larger maximum tumor diameter (p = 0.003) and a tendency of capsular invasion (p = 0.0542) but possibly unrelated to central lymph node metastasis (p = 0.1846). Nodular goiters accounted for most benign entities initially designated as Bethesda categories III-V.

CONCLUSION

BRAF V600E mutational analysis complements cytopathology and improves the PTC detection rate in FNA cytology samples due to the high prevalence of the mutation in China. BRAF V600E mutation does not show a statistical correlation with tumor aggressiveness. Morphological pitfalls such as histocyte aggregation, cystic-lining cells in nodular goiters, and oncocytes in Hashimoto's thyroiditis, were overwhelmingly found in BRAF V600E-negative specimens.

Preoperative evaluation of thyroid nodules - Diagnosis and management strategies

Thyroid cancer is the most common endocrine malignancy, with increasing incidence over the past few decades. Fine needle aspiration (FNA) biopsy is the gold standard for preoperative diagnosis of thyroid malignancies. Nevertheless, this method renders indeterminate results in up to 30% of the cases. Therefore, these patients are often referred to unnecessary surgery to establish the diagnosis. To improve the accuracy of preoperative diagnosis, several other ways, such as ultrasonography, elastography, immunohistochemical analysis, genetic testing, and core needle biopsy, have been developed and can be used either in association with or as an alternative to FNA. This review aims to evaluate all these diagnostic tools to determine the most appropriate way of managing thyroid nodules and subsequently improve the selection of cases referred to surgery.

The diagnostic value of add-on thyroid cell block in the evaluation of thyroid lesions

Objectives

Fine-needle aspiration (FNA) cytology plays a pivotal role in diagnosing thyroid nodules. Imaging assessment, followed by thyroid lesion sampling, is a widely applied clinical practice. Tissue fragments remnants are retrieved in cell-block providing an adjunct diagnostic tool for histopathology visualization and use of ancillary testing. This study aimed to evaluate whether the auxiliary application of cell-block adds to the diagnostic accuracy of the thyroid FNA.

Material and Methods

A total of 252 thyroid FNA cases between (2020 and 2021) were reviewed from patients aged 18-76. Of those, 150 cell-blocks were recovered and examined to assess their utility. Following categories were plotted during cell-blocks revision: (A) Inadequate material retrieved; (B) cell-block shows similar features along with their accompanying smears; and (C) value added to cytology diagnosis when using cell-block.

Results

The distribution of cell-blocks according to the aforementioned classification are as follows: A - non-diagnostic 63%, B - similar observation seen in both preparations 35%, and C - value added to the rendered diagnosis 2%. Hence, the use of cell-block improved cytology diagnosis in only 2% of total cases. Mostly were of immunostains application for diagnosis confirmation.

Conclusion

The non-diagnostic and atypical cytology cases have not been upgraded to a more meaningful category by the incorporation of cell-block performed with the routine non-enhancement random method. On the other hand, cell-blocks contributed generously toward immunostaining application in malignant scenarios.

Utility of cell block as an adjunct to liquid-based cytology for diagnosing papillary thyroid carcinoma

Background

Although liquid-based cytology (LBC) has gained popularity among clinical laboratories, it is unclear whether it is equivalent to conventional smears for making a definite diagnosis of papillary thyroid carcinoma (PTC). The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) suggests a definite diagnosis of PTC is preferred when there are at least one of three features (papillary architecture, psammomatous calcifications, and frequent pseudonuclear inclusions) plus other typical cytomorphological findings. This study evaluated whether an additional cell block (CB), prepared from the residual LBC material, could help improve the diagnosis of PTC.

Materials and Methods

A total of 62 cases with both ThinPrep LBC and CB preparations and histopathological follow-up of PTC were retrieved between November 2016 and March 2019. The ThinPrep LBC and CB slides were reviewed separately to identify any papillary architecture, psammomatous calcifications, or pseudonuclear inclusions for diagnosing PTC.

Results

Among the 51 cases with cytological diagnosis of PTC in the LBC+CB slides, the CB provided additional diagnostic information in 15 cases, which were initially diagnosed as suspicious for PTC based on the LBC slides alone. This information included papillary architecture (n=11), psammomatous calcification (n=1) and pseudonuclear inclusions (n=5). The number of specimens in the 51 cases containing at least one of the three features increased from 42 (LBC) to 51 (LBC+CB). The accuracy for diagnosing PTC increased from 58.1% for LBC alone to 82.3% for the LBC+CB examination.

Conclusion

An adjunctive CB preparation may improve the LBC technique for diagnosing PTC.

The KWAK TI-RADS and 2015 ATA guidelines for medullary thyroid carcinoma: Combined with cell block-assisted ultrasound-guided thyroid fine-needle aspiration

OBJECTIVE

To compare the value of the thyroid imaging reporting and data system proposed by Kwak (KWAK TI-RADS) and the 2015 American Thyroid Association (ATA) guidelines for diagnosis of medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC). To confirm the role of cell block (CB)-assisted fine-needle aspiration (FNA) in final diagnosis of MTC.

DESIGN

Retrospective hospital-based cohort study.

PATIENTS

Ninety-three patients with 29 MTCs, 31 PTCs and 33 thyroid adenomas (TAs) who underwent thyroidectomy from January 2010 to May 2019 were retrospectively reviewed. The KWAK TI-RADS and ATA guidelines were used to assess each thyroid nodule. FNA, CB-assisted FNA and core needle biopsy (CNB) were performed in final diagnosis.

RESULTS

Age and ultrasound features (composition, echogenicity and shape) were significantly different between MTC and PTC. Sex and ultrasound features (echogenicity, margin and calcification) were significantly different between MTC and TA. The KWAK TI-RADS and ATA guidelines showed no significant difference for MTC (area under the curve [AUC]: 0.812 and 0.808; P = .37-.85) or PTC (AUC: 0.883 and 0.885; P = .25-.96). The KWAK TI-RADS and ATA guidelines showed high specificity and sensitivity for MTC (93.9% and 62.1%, 87.9% and 65.5%) and PTC (93.9% and 67.7%, 87.9% and 77.4%), respectively. For suspicious MTC (7 cases), CB-assisted FNA provide accuracy preoperative diagnosis.

CONCLUSIONS

Although the diagnostic performance of the TI-RADS and ATA guidelines is worse for MTC than PTC, the difference is not statistically significant. CB-assisted FNA should be performed in thyroid nodules with 4a or lower suspicion to avoid misdiagnosis of MTC.

A comparative study of two liquid-based preparation methods: membrane-based and sedimentation in fine needle aspiration cytology diagnosis in thyroid nodules

Background

As thyroid fine needle aspiration (FNA) shows a certain limitation in the diagnosis of conventional smears, novel approaches like liquid-based cytology (LBC) have been gradually applied recently. Studies have shown the difference between the conventional smears (CSs) and liquid-based smears on fine needle aspiration cytology (FNAC) diagnosis, but the impacts of different liquid-based preparation (LBP) methods, including membrane-based and sedimentation, on diagnosis are still not clear. In this study, the effects of liquid-based smears prepared by different methods on the cytological interpretation were studied.

Methods

A total of 221 thyroid liquid-based FNAC cases from January 2017 to October 2018 were collected. We retrospectively studied and compared the effects of the membrane-based and sedimentation LBP methods through The Bethesda System for Reporting Thyroid Cytopathology (TBS) diagnosis and risk of malignancy assessment. Besides, we made an evaluation on the diagnostic differences in the effects of different preparation methods on the cell morphology and tissue structure of papillary thyroid carcinoma (PTC) for more accurate FNAC diagnosis.

Results

Among the 221 cases reviewed, membrane-based method was applied in 153 cases and sedimentation in 68 cases. According to the diagnostic criteria of 2017 TBS, TBSVI and TBSV thyroid could be cytologically diagnosed by membrane-based (49.0% (75/153) and 25.5% (39/153)) and sedimentation (52.9(36/68) and 25(17/68)) methods, and both were confirmed as PTC through histopathological diagnosis after operation, with the malignancy degree as high as 100%. In addition, of the 30 cases that were diagnosed as TBSIII thyroid nodules with the membrane-based method, 15 cases were pathologically malignant after an operation, with the malignancy degree of 50% (15/30), while that in 11 cases using the sedimentation method was 45.4% (5/11). PTC could be detected in both the TBSIV and TBSII thyroid nodules diagnosed by membrane-based method, with the sensitivity of 87.0% (114/131) lower than that by sedimentation method (91.4% (53/58)), showing the lower consistency with the histopathological result (K = 0.635 vs K = 0.757). Among the membrane-based smears, 23.5% (36/153) had fewer follicular epithelial cells, 55.6% (20/36) of which were considered to be suspicious for PTC from cell karyotype and tissue arrangement. While among the sedimentation smears, 16.2% (11/68) had fewer follicular epithelial cells, and 63.6% (7/11) was suspicious for PTC. In 72.5% (95/131) membrane-based smears of PTC, the papillary and swirling structures were not obvious, showing as crowded syncytial cell masses, while in 55.2% (32/58) sedimentation smears, both structures were visible with obvious three-dimensional papillary structure, and the fibrovascular axis still remained.

Conclusion

LBP technique is feasible for FNAC diagnosis, and the sedimentation shows more advantages, like higher PTC detection rate and good consistency with postoperative histopathological diagnosis. A clear understanding of the subtle differences in the effects of membrane-based and sedimentation methods on the cell morphology and tissue structure could be conducive to the definitive diagnosis of PTC before operation.

Diagnostic utility of cell block in fine needle aspiration cytology of thyroid gland

BACKGROUND

This study was conducted to evaluate the diagnostic utility of cell block material in fine needle aspiration (FNA) of thyroid nodules.

DESIGN

A total of 242 thyroid fine need aspirations (FNAs) were performed between January 2015 and December 2015. Of those, all consecutive thyroid FNA cases with cell blocks (n = 140) from 129 patients (age: 58.9 ± 12.8 years) are included in this study. Cytology slides and cell blocks are reviewed for adequacy assessment based on the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) and then categorizing them into TBSRTC diagnostic categories. These cases are divided into two groups, combined cytology and cell block (C + CB) and cytology without cell block (C).

RESULTS

In the first group (C + CB), a total 140 cases are categorized in TBSRTC as follows: I: 13 (9.3%) cases, II: 78 (55.7%) cases, III: 7 (5%), IV: 16 (11.4%), V: 3(2.2%) and VI: 23 (16.4%). In the second group (C), the cases are classified in TBSRTC as follows: I: 23 (16.4%) cases, II: 70 (50%), III: 7 (5%), IV: 16 (11.4%), V: 3 (2.2%) and VI: 21 (15%). Nondiagnostic rate was 7.1% lower in the first group (C + CB) as compared with second group (C) (First group: 9.3% vs second group: 16.4%, P = .0764).

CONCLUSIONS

Combined use of cytology slides and cell block decreases the nondiagnostic rate up to 7.1% as compared with cytology without cell block.