A Different Perspective on Evaluating the Malignancy Rate of the Non-Diagnostic Category of the Bethesda System for Reporting Thyroid Cytopathology: A Single Institute Experience and Review of the Literature

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.

Diagnostic Value of Preparing Additional Liquid-Based Cytology Slides and Cell Blocks from Residue Material in Thyroid fine Needle Aspiration

Background and Aims

After liquid-based cytology (LBC) technique developed for cervical cytology, it has been used for nongynecological samples and has been very successful. It offers having extra slides of the samples for further examination and ancillary tests. Moreover, cell blocks can be formed from the residue material. The study aimed to evaluate the importance of preparing a second LBC slide or a cell block from the residue material of thyroid fine needle aspiration (FNA) samples to reach a definitive diagnosis in cases diagnosed as nondiagnostic (ND) after the first slide.

Material and Methods

Seventy five cases diagnosed as ND after the first slide were included in study. For 50 cases, the second LBC slides were prepared (LBC group); for 25 cases, cell block was performed from residue material (CB group). Two groups were compared in terms of reaching a definitive diagnosis.

Results

At the end of secondary procedures, a definitive diagnosis was reached in a total of 24 cases (32%). Twenty of 50 cases (40%) in LBC group reached a definitive diagnosis while four cases (16%) in the CB group reached a definitive diagnosis. Achieving a definitive diagnosis was found statistically higher in the LBC group in which the second slide was formed compared to the CB group (P =0.036).

Conclusion

Preparing a second slide with LBC method is more purposive than preparing a cell block from the residue material of thyroid FNA samples. Reducing the percentage of ND cases will protect patients from complications and morbidity that may arise from repeated FNA.

The Evaluation of Malignancy Rates of Nondiagnostic Cases in Thyroid Fine-Needle Aspirations

Aim: In this study, it was aimed to investigate the malignancy rates of nondiagnostic (ND) thyroid fine-needle aspiration cytology (FNAC) material by evaluating either the result of the second FNAC or resection/biopsy materials.Method: Among the 1165 thyroid FNAC cases evaluated in the Pathology Department of Başakşehir Çam and Sakura City Hospital within 9 months (October 2020-June 2021), 102 cases (8,7%) diagnosed with ND were included in the study. At the end of the 6-15 months follow-up period after the diagnosis of ND, the results of the second FNAC or resection (thyroidectomy, lobectomy)/biopsy of the cases were evaluated. Diameter and sonographic features of thyroid nodules (solid, cystic, mixed) were also noted.Results: 49% of the cases (n:50) had a second FNAC. Resection/biopsy was performed in only 12 (11,8%) cases. Of these 62 cases, 39 were diagnosed by second FNAC and 7 by resection/biopsy as benign (74,1%), and 5 cases were diagnosed as malignant by resection/biopsy. 7 cases were diagnosed as nondiagnostic again after the second FNAC. Final diagnosis (by resection) of the case whose second FNAC result was reported as suspicious for malignancy was papillary microcarcinoma. This case was included in the group ‘diagnosed as malignant only by resection/biopsy. In other words, malignancy was detected in 5 of 62 patients who underwent a second FNAC or resection/biopsy. The risk of malignancy was found to be 8% in the patient population included in the study with the diagnosis of ND.Conclusion: A low rate of NE results were found in this ultrasound-guided thyroid series (8,7%). After the second FNAC or resection, malignancy rates was found to be 8%. Although this result is compatible with the results of some studies, it is considerably lower than others. It would be appropriate to follow up on ND nodules with their clinical/sonographic features. Additional studies with large series will be more helpful in determining the malignancy rates of the ND group.

US-guided FNA techniques for thyroid nodules is the short axis better than the long axis?

BACKGROUND

Ultrasound-guided fine needle aspiration cytology (FNAC US) has been proven to be an accurate and efficient tool in thyroid nodule evaluation. Thyroid nodule aspiration can be acquired with either of two techniques: the short axis, in which only the tip of the needle is observed, and the long axis, in which the entire length of the needle is observed. Our retrospective study aimed to compare the adequacy of the two techniques.

METHODS

FNAC US was performed in 538 thyroid nodules between January 2019 and December 2021. Data on the technique and the diagnostic accuracy were collected.

RESULTS

A total of 273 nodules were aspirated using the long axis technique, and 265 nodules were aspirated using the short axis technique. The diagnostic adequacies of the long axis technique were significantly higher than those of the short axis technique (92 % versus 86 %, respectively, p < 0.025).

CONCLUSION

In our study, the long axis technique provided more accurate cytological evaluation than the short axis technique.

LEVEL OF EVIDENCE

level 3.

The Bethesda System for Reporting Thyroid Cytopathology: A Cytohistological Study

Introduction

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) is a significant step to standardize the reporting of thyroid fine needle aspiration (FNA). It has high predictive value, reproducibility, and improved clinical significance.

Aim

The study was aimed to evaluate the diagnostic utility and reproducibility of "TBSRTC" at our institute. Methods and Material. The study included 646 thyroid FNAs which were reviewed by three pathologists and classified according to TBSRTC. Cytohistological correlation was done for 100 cases with surgical follow-up and the sensitivity, specificity, positive predictive value, negative predictive value, diagnostic accuracy, and risk of malignancy (ROM) were calculated. The interobserver variation among three pathologists was also assessed.

Results

The distribution of cases in various TBSRTC categories is as follows: I-nondiagnostic 13.8%, II-benign 75.9%, III-atypia of undetermined significance (AUS)/follicular lesion of undetermined significance (FLUS) 1.2%, IV-follicular neoplasm (FN)/suspicious for follicular neoplasm (SFN) 3.7%, V-suspicious for malignancy (SM) 2.6%, and VI-malignant 2.8%. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy are 72.4%, 94.3%, 84%, 89.2%, and 87.9%, respectively. The ROM of various TBSRTC categories were II-8.5%; III-66.7%; IV-63.6%; and V and VI-100%. Cohen's Weighted Kappa score was 0.99 which indicates almost perfect agreement among the three pathologists.

Conclusions

Our study substantiates greater reproducibility among pathologists using TBSRTC to arrive at a precise diagnosis with an added advantage of predicting the risk of malignancy which enables the clinician to plan for follow-up or surgery and also the extent of surgery.

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.