The Role of CD56 in Thyroid Fine Needle Aspiration Cytology: A Pilot Study Performed on Liquid Based Cytology

Paving the path toward multi-omics approaches in the diagnostic challenges faced in thyroid pathology

INTRODUCTION

Despite advancements in diagnostic methods, the classification of indeterminate thyroid nodules still poses diagnostic challenges not only in pre-surgical evaluation but even after histological evaluation of surgical specimens. Proteomics, aided by mass spectrometry and integrated with artificial intelligence and machine learning algorithms, shows great promise in identifying diagnostic markers for thyroid lesions.

AREAS COVERED

This review provides in-depth exploration of how proteomics has contributed to the understanding of thyroid pathology. It discusses the technical advancements related to immunohistochemistry, genetic and proteomic techniques, such as mass spectrometry, which have greatly improved sensitivity and spatial resolution up to single-cell level. These improvements allowed the identification of specific protein signatures associated with different types of thyroid lesions.

EXPERT COMMENTARY

Among all the proteomics approaches, spatial proteomics stands out due to its unique ability to capture the spatial context of proteins in both cytological and tissue thyroid samples. The integration of multi-layers of molecular information combining spatial proteomics, genomics, immunohistochemistry or metabolomics and the implementation of artificial intelligence and machine learning approaches, represent hugely promising steps forward toward the possibility to uncover intricate relationships and interactions among various molecular components, providing a complete picture of the biological landscape whilst fostering thyroid nodule diagnosis.

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.

Systematic Review and Meta-Analysis to Identify the Immunocytochemical Markers Effective in Delineating Benign from Malignant Thyroid Lesions in FNAC Samples

Conventional cytology-based diagnosis for thyroid cancer is limited with more than 30-45% of nodules categorized as indeterminate, necessitating surgery for confirming or refuting the diagnosis. This systematic review and meta-analysis were aimed at identifying immunocytochemical markers effective in delineating benign from malignant thyroid lesions in fine needle aspiration cytology (FNAC) samples, thereby improving the accuracy of cytology diagnosis. A systematic review of relevant articles (2000-2021) from online databases was carried out and the search protocol registered in PROSPERO database (CRD42021229121). The quality of studies was assessed using QUADAS-2. Review Manager 5.4.1 from Cochrane collaboration and MetaDisc Version 1.4 was used to conduct the meta-analysis. Bias in the studies were visually analyzed using funnel plots, and statistical significance was evaluated by Egger's test. Systematic review identified 64 original articles, while meta-analysis in eligible articles (n = 41) identified a panel of 5 markers, Galectin-3, HBME-1, CK-19, CD-56, and TPO. Assessment of the diagnostic performance revealed that Gal-3 (sensitivity: 0.81; CI: 0.79-0.83; specificity: 0.84; CI: 0.82-0.85) and HBME-1 (sensitivity: 0.83; Cl: 0.81-0.86; specificity: 0.85; CI: 0.83-0.86) showed high accuracy in delineating benign from malignant thyroid nodules. Efficacy analysis in indeterminate nodules showed Gal-3 and HBME-1 have high specificity of 0.86 (CI 0.84-0.89) and 0.82 (CI 0.78-0.86), respectively, and low sensitivity of 0.76 (CI 0.72-0.80) and 0.75 (CI 0.70-0.80), respectively. Diagnostic odds ratio (DOR) of Galectin-3 and HBME-1 were 39.18 (CI 23.38-65.65) and 24.44 (CI 11.16-53.54), respectively. Significant publication bias was observed for the markers Galectin-3 and CK-19 (p < 0.05). The panel of 5 markers identified from this meta-analysis are high-confidence candidates that need to be validated in thyroid cytology to establish their efficacy and enable clinical applicability.

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.

To Obtain More With Less: Cytologic Samples With Ancillary Molecular Techniques-The Useful Role of Liquid-Based Cytology

CONTEXT

- Fine-needle aspiration cytology has been increasingly used as the first tool in the evaluation of several diseases. Although cytology has a relevant role in the discrimination between benign and malignant lesions, conventional slides cannot lead to 100% conclusive results. It was hoped that the introduction of liquid-based cytology (LBC) would improve the efficacy of cytology through standardization, quality improvement, and the possibility of carrying out ancillary techniques on the residual stored material. In recent decades, the application of genomic alterations has been studied on cytologic samples with feasible and reliable results. The molecular analysis offers a powerful aid to define the best clinical or surgical approaches and follow-up for patients. In recent years, the application of different ancillary techniques has been carried out on conventional slides even though LBC represents a useful additional and alternative method for molecular testing.

OBJECTIVE

- To demonstrate the relevance of LBC as a valid aid to overcoming the difficulties encountered in the application of ancillary techniques on conventional slides.

DATA SOURCES

- We examined and reviewed our experience with the application of ancillary techniques on LBC performed on different body sites.

CONCLUSIONS

- We emphasize that LBC achieves significant and accurate results. It represents a valid method for cytologic evaluation and it provides highly reproducible and informative molecular yields.

Update on: proteome analysis in thyroid pathology - part II: overview of technical and clinical enhancement of proteomic investigation of the thyroid lesions

INTRODUCTION

An accurate diagnostic classification of thyroid lesions remains an important clinical aspect that needs to be addressed in order to avoid 'diagnostic' thyroidectomies. Among the several 'omics' techniques, proteomics is playing a pivotal role in the search for diagnostic markers. In recent years, different approaches have been used, taking advantage of the technical improvements related to mass spectrometry that have occurred. Areas covered: The review provides an update of the recent findings in diagnostic classification, in genetic definition and in the investigation of thyroid lesions based on different proteomics approaches and on different type of specimens: cytological, surgical and biofluid samples. A brief section will discuss how these findings can be integrated with those obtained by metabolomics investigations. Expert commentary: Among the several proteomics approaches able to deepen our knowledge of the molecular alterations of the different thyroid lesions, MALDI-MSI is strongly emerging above all. In fact, MS-imaging has also been demonstrated to be capable of distinguishing thyroid lesions, based on their different molecular signatures, using cytological specimens. The possibility to use the material obtained by the fine needle aspiration makes MALDI-MSI a highly promising technology that could be implemented into the clinical and pathological units.

Current methodologies for molecular screening of thyroid nodules

Several molecular tests have been developed for thyroid cytology with the main purpose to define the nature of indeterminate nodules in presurgical phase thus overcoming the limitations of cytological analysis. Molecular tests currently available for thyroid nodules are based on a variety of methodologies and display peculiar strengths and limitations: in this review of the literature they are summarized and critically discussed. The use of molecular diagnostics for thyroid cytology is increasingly widespread and accepted, however large, prospective validation studies are still needed to ultimately demonstrate the clinical efficacy of a wide incorporation of molecular tests into clinical practice.

Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features: Can Cytology Face the Challenge of Diagnosis in the Light of the New Classification?

OBJECTIVES

To assess the cytological findings of noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP), conventional papillary thyroid carcinomas (C-PTC), and invasive follicular variants of papillary thyroid carcinomas (IFV-PTC) to determine if there are cytological differences between groups.

STUDY DESIGN

We have reviewed all thyroid fine-needle aspiration cytology samples diagnosed between 2000 and 2017. We have included all NIFTP cases (n = 6) and randomly selected cases of C-PTC (n = 14) and IFV-PTC (n = 8).

RESULTS

Comparing NIFTP and C-PTC cases, NIFTP cases showed significantly less papillary or pseudopapillary architecture, more bidimensional groups and microfollicles, and less tridimensionality, giant cells, and nuclear folds. We observed a trend towards significance for smear cellularity and amount of cytoplasm. Presence of nuclear folds was the only significant difference between NIFTP and IFV-PTC cases. The differences between groups in percent papillary or pseudopapillary architecture, cellularity, and tridimensionality showed a trend towards significance. Amount of colloid, dirty background, pleomorphism or atypia, nuclear pseudoinclusions, type of chromatin, and nucleolus were not significant.

CONCLUSIONS

No cytopathological feature can differentiate between invasive and encapsulated IFV-PTC. In accordance with the recently accepted category, PTC smears with cells arranged in a predominantly follicular architecture should be reported as Bethesda IV category with descriptive terms to avoid false-positive cases.

Diagnostic importance of CD56 with fine-needle aspiration cytology in suspected papillary thyroid carcinoma cases

Background

Palpable thyroid nodules can be found in 4%-7% of the adult population; however, <5% of thyroid nodules are malignant. Immunohistochemical markers, such as CD56, can be used to make a differential diagnosis between benign and malignant lesions. To increase the accuracy of the diagnosis and distinguish the malignant aspirates from the benign ones, chose to evaluate CD56, which is normally found in benign thyroid tissue.

Methods

A total of 53 fine-needle aspirate samples from patients diagnosed with suspected papillary thyroid carcinoma (PTC) were included prospectively. These aspirates were immunocytochemically stained for CD56.

Results

In histopathological examination, the fine-needle aspiration cytopathology specimens suspicious for PTC (after undergoing surgery) showed that 32 (60.4%) were benign and 21 (39.6%) were malignant. Thirty-one of the benign cases (96.87%) were CD56-positive, whereas the last case (3.13%) was CD56-negative. Staining was not seen in any of the malignant cases.

Conclusions

We believe that CD56 is an important marker in the definitive diagnosis of suspected PTC cases, with CD56-positivity being interpreted in favor of benignity.

Diagnostic significance of CK19, galectin-3, CD56, TPO and Ki67 expression and BRAF mutation in papillary thyroid carcinoma

The aim of the present study was to examine the rate of BRAF mutation and the expression profiles of CK19, galectin-3, CD56, thyroid peroxidase (TPO) and Ki67 in papillary thyroid carcinoma (PTC) and papillary thyroid micro-carcinoma (PTMC). A total of 246 cases of thyroid disease were collected, including PTC, PTMC, nodular goiter (NG) and Hashimoto thyroiditis (HT). The results revealed that CK19 expression was 116/120 in PTC, 61/64 in PTMC, 2/34 in NG and 1/28 in HT. Galectin-3 positive expression was 115/120 in PTC, 60/64 in PTMC, 6/34 in NG and 4/28 in HT. TPO positive expression was 8/120 in PTC, 1/64 in PTMC, 30/34 in NG and 25/28 in HT. CD56-positive expression was 12/120 in PTC, 3/64 in PTMC, 33/34 in NG and 26/28 in HT. Ki67 labeling index was 2.52±0.46% in PTC (120 cases), 2.62±0.52% in PTMC (64 cases), 2.55±0.44% in NG (34 cases) and 2.58±0.48% in HT (28 cases). BRAF mutation rate was 93/120 in PTC, 47/64 in PTMC, 3/34 in NG and 2/28 in HT. These results suggested that expression patterns of CK19, galectin-3, CD56 and TPO and BRAF mutation exhibit diagnosis value in thyroid disease. However, Ki67-positive rate exhibits no notable diagnosis value in thyroid disease.

BRAFK601E Mutation in a Follicular Thyroid Adenoma: A Case Report

BRAF mutations represent the most common genetic alteration in papillary thyroid carcinoma (PTC). The p.V600E mutation is specific for the classic and tall-cell variants of PTC and has been associated with a more aggressive biologic behavior. On the other hand, the p.K601E mutation is peculiar to the follicular variant of PTC, and seems to be a favorable prognostic indicator. A 12-year-old boy presented with a 10-mm left-sided thyroid nodule. Fine-needle aspiration cytology reported the lesion as suspicious for a follicular neoplasm (Bethesda category IV). The patient underwent lobectomy, and histopathology revealed a follicular adenoma with normal surrounding tissue. The cytological smear was found to be positive for BRAF p.K601E mutation, and this was later confirmed on the corresponding paraffin block. This case was independently revised by 4 expert pathologists, all of whom confirmed the benign nature of the thyroid lesion. This article describes the presence of a BRAF mutation in a benign thyroid lesion. To the authors' knowledge, this is the fourth case of follicular adenoma carrying BRAF^K601E reported in literature to date. BRAF^K601E mutation can occur in benign thyroid lesions. This finding, in the context of the current literature and the recently proposed reclassification of the noninvasive encapsulated follicular variant of papillary thyroid carcinoma into a benign lesion, confirms the importance of preoperative BRAF p.K601E testing in offering patients a tailored treatment plan and avoiding overtreatment.

Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)

Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is a new term replacing what was previously known as non-invasive encapsulated follicular variant of papillary thyroid carcinoma (FVPTC). These tumors show benign/indolent clinical behavior when compared with invasive FVPTC, which led to their reclassification as a "non-malignant" neoplasm. NIFTP shares essentially similar cytomorphologic features as FVPTC, and can only be definitively diagnosed on surgical excision specimens. This article provides an update on morphologic characteristics of NIFTP, along with pertinent molecular studies and management algorithms.

The role of miRNAs in the evaluation of follicular thyroid neoplasms: an overview of literature

MicroRNA (miRNA) deregulation has been frequently associated with different human cancers. Not only have miRNAs been involved in almost every cellular function but they have also been linked with a significant number of cancers including thyroid carcinomas. Specifically, thyroid tumors encompass several different miRNA profiles based on the histotypes. Furthermore, thyroid lesions with their broad spectrum of neoplasms (from benign to malignant entities) offer the possibility of studying and recognizing specific subsets of different up-and downregulated miRNAs in each different entity. To date, the majority of authors completed their evaluation mostly by including histologic samples of thyroid tumors. Nonetheless, in the last years, a few studies are focusing on the role of miRNA expression in thyroid fine-needle aspiration cytology (FNAC) regardless of the cytologic preparation, including liquid-based cytology. This growing interest is driven by the possible role of miRNAs in the malignant risk stratification, especially for the indeterminate categories of follicular neoplasms (FNs). In this review we overview the reliability of analyzing miRNAs on thyroid lesions, including those diagnosed as FNs, to identify whether their profiles are likely to distinguish benign from malignant lesions, providing a predictive molecular diagnosis on FNAC.

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.