Are we ready to modify the Bethesda thyroid fine-needle aspiration classification scheme?

Revised Bethesda System for Reporting Thyroid Cytology: Lessons learned from an appraisal of 5 years of experience in a central hospital

OBJECTIVE

The Bethesda System for Reporting Thyroid Cytology (BSFRTC) is widely adopted in the management of thyroid nodules. The system was updated in 2017, and its impact is the subject of this paper.

METHODS

All thyroid fine needle aspirations from 2016-2020 using the BSFRTC, with follow-up surgical pathology, were reviewed. The risk of neoplasia (RON), risk of malignancy (ROM), RON/ROM ratio, and surgical follow-up rate were determined for each diagnostic category with cytohistological correlation. ROM was calculated in two separate manners, with non-invasive follicular tumours with papillary-like nuclear features (NIFTP) counted as malignant or non-malignant. Sensitivity, specificity, negative and positive predictive values were determined for indeterminate categories: atypia of undetermined significance (AUS), suspicious for follicular neoplasm (SFN), and suspicious for malignancy (SFM).

RESULTS

RON, ROM, and the surgical follow-up rate increased steadily from the benign through intermediate to malignant categories. The omission of NIFTP from malignant lesions reduced the calculated ROM in indeterminate categories and improved the stratification between AUS and SFN. ROM in AUS was distinct from SFN. AUS has a well-balanced sensitivity and specificity favouring a screening rather than a diagnostic category. The calculated RON/ROM was significantly higher in AUS (1.56), compared to SFN (1.03) and SM (1.05), in agreement with current BSRTC management recommendations.

CONCLUSIONS

AUS is an important screening category and should remain with the addition of subcategorisation. RON and surgical follow-up rates are essential quality indicators. The RON/ROM ratio could be utilised to determine appropriate management for each diagnostic category on an institutional basis.

Cytopathology of Follicular Cell Nodules

The detection of thyroid nodules, consisting of different diseases, represents a common finding in population. Their evaluation and diagnosis are mostly achieved with fine-needle aspiration cytology (FNAC). Even though the majority of thyroid nodules are correctly diagnosed, a total of 25% to 30% of them are classified "indeterminate" comprising lesions with varying risk of malignancy and different types of management. Although the number of thyroid FNACs, including small lesions, is increasing due to the reliance upon sonographic and cytologic interpretations, there are issues concerning cytomorphologic interpretation and interobserver reproducibility. Different classification systems have tried to better define the criteria for inclusion in specific categories and to therefore reduce the rate of indeterminate diagnoses such as atypia of undetermined significance, follicular neoplasms, and suspicious for malignancy. However, the support of ancillary techniques (eg, immunocytochemistry and molecular analysis) are reshaping morphologic diagnoses made on materials obtained from FNAC.

The cytological diagnosis of a 'benign thyroid lesion': is it a real safe diagnosis for the patient?

OBJECTIVE

In fine needle aspiration cytology (FNAC), the category of benign thyroid lesions (BTL), which constitutes 65-70% of all thyroid FNAC, and can be correctly diagnosed by morphology alone, is an important entity. A diagnosis of BTL denotes a lesion managed with follow-up unless found in conjunction with compressive symptoms. Although this diagnosis can be quite simple, there are cases in which the scant cellular or colloid component may pose diagnostic issues. Herein, we describe the experiences of evaluating BTL at two large academic institutions. We evaluated the clinical importance of a correct diagnosis of BTL to define the exact inherent risk of a false-negative result (FNR).

METHODS

From January 2008 through to June 2013, 506 (3.6%) out of 15 850 patients with BTL underwent surgery. All nodules were sampled under sonographic guidance (US) and processed either with liquid-based cytology (LBC), Diff-Quik® smears or alcohol-Papanicolaou staining methods.

RESULTS

The histological follow-up of 506 BTL series included 493 benign and 13 malignant lesions. The latter group included four follicular carcinomas (FC), two classic variants of papillary thyroid carcinoma (PTC), one macrofollicular PTC and six follicular variants of PTC (FVPC). The malignancy rate for the BTL category was 2.5%.

CONCLUSIONS

When diagnosed by expert cytopathologists, BTL represents a robust diagnosis and might reduce the number of FNR. Additional diagnostic experience and a large case series could enable cytopathologists to recognise all the morphological entities of BTL. An important additional aid is the extensive sampling of the lesions to reduce issues related to a low cellularity.

The nightmare of indeterminate follicular proliferations: when liquid-based cytology and ancillary techniques are not a moon landing but a realistic plan

OBJECTIVE

Thyroid nodules are a common finding in the general population, including both nonneoplastic and neoplastic entities. Fine-needle aspiration cytology (FNAC) is the first tool for evaluating thyroid nodules. In spite of its high diagnostic accuracy, 25% of nodules result in the category of follicular neoplasms (FN), with varying risk of malignancy and different management strategies.

STUDY DESIGN

The use of ancillary techniques is reshaping the practice of FNAC. These tools can significantly empower the morphological diagnosis and prognosis of thyroid nodules, allowing a more accurate prediction of the nature of the lesion. Several studies have underlined the role of single or multiple testing for the category of FN as strong indicators of cancer. Every cytological preparation can be used for the application of ancillary techniques but the introduction of liquid-based cytology (LBC) might facilitate the application.

RESULTS

Our experience involving an immunocytochemical panel made up of HBME-1 and galectin-3 pointed to an 81% overall diagnostic accuracy in discriminating between low and high risk of malignancy in FN.

CONCLUSIONS

The application of these techniques on LBC represents an adjunct to the morphological evaluation of FN. They represent a critical and challenging, but also a feasible, tool in the preoperative diagnoses, allowing specific prognostic and predictive details regardless of the cytological preparation. © 2014 S. Karger AG, Basel.