Triage of the indeterminate thyroid aspirate: What are the options for the practicing cytopathologist?

Comparison of the diagnostic effectiveness of ultrasound imaging coupled with three mathematical models for discriminating thyroid nodules

BACKGROUND

The overlapping nature of thyroid lesions visualized on ultrasound (US) images could result in misdiagnosis and missed diagnoses in clinical practice.

PURPOSE

To compare the diagnostic effectiveness of US coupled with three mathematical models, namely logistic regression (Logistics), partial least-squares discriminant analysis (PLS-DA), and support vector machine (SVM), in discriminating between malignant and benign thyroid nodules.

MATERIAL AND METHODS

A total of 588 thyroid nodules (287 benign and 301 malignant) were collected, among which 80% were utilized for constructing the mathematical models and the remaining 20% were used for internal validation. In addition, an external validation cohort comprising 160 nodules (80 benign and 80 malignant) was employed to validate the accuracy of these mathematical models.

RESULTS

Our study demonstrated that all three models exhibited effective predictive capabilities for distinguishing between benign and malignant nodules, whose diagnostic effectiveness surpassed that of the TI-RADS classification, particularly in terms of true negative diagnoses. SVM achieved a higher diagnostic rate for malignant thyroid nodules (93.8%) compared to Logistics (91.5%) and PLS-DA (91.6%). PLS-DA exhibited higher diagnostic rates for benign thyroid nodules (91.9%) compared to Logistics (86.7%) and SVM (88.7%). Both the area under the receiver operating characteristic curve (AUC) values of PLS-DA (0.917) and SVM (0.913) were higher than that of Logistics (0.891).

CONCLUSION

Our findings indicate that SVM had significantly higher rates of true positive diagnoses and PLS-DA exhibited significantly higher rates of true negative diagnoses. All three models outperformed the TI-RADS classification in discriminating between malignant and benign thyroid nodules.

Emerging Biomarkers in Thyroid Practice and Research

Simple Summary

Tumor biomarkers are molecules at genetic or protein level, or certain evaluable characteristics. These help in perfecting patient management. Over the past decade, advanced and more sensitive techniques have led to the identification of many new biomarkers in the field of oncology. A knowledge of the recent developments is essential for their application to clinical practice, and furthering research. This review provides a comprehensive account of such various markers identified in thyroid carcinoma, the most common endocrine malignancy. While some of these have been brought into use in routine patient management, others are novel and need more research before clinical application.

Abstract

Thyroid cancer is the most common endocrine malignancy. Recent developments in molecular biological techniques have led to a better understanding of the pathogenesis and clinical behavior of thyroid neoplasms. This has culminated in the updating of thyroid tumor classification, including the re-categorization of existing and introduction of new entities. In this review, we discuss various molecular biomarkers possessing diagnostic, prognostic, predictive and therapeutic roles in thyroid cancer. A comprehensive account of epigenetic dysregulation, including DNA methylation, the function of various microRNAs and long non-coding RNAs, germline mutations determining familial occurrence of medullary and non-medullary thyroid carcinoma, and single nucleotide polymorphisms predisposed to thyroid tumorigenesis has been provided. In addition to novel immunohistochemical markers, including those for neuroendocrine differentiation, and next-generation immunohistochemistry (BRAF V600E, RAS, TRK, and ALK), the relevance of well-established markers, such as Ki-67, in current clinical practice has also been discussed. A tumor microenvironment (PD-L1, CD markers) and its influence in predicting responses to immunotherapy in thyroid cancer and the expanding arena of techniques, including liquid biopsy based on circulating nucleic acids and plasma-derived exosomes as a non-invasive technique for patient management, are also summarized.

Immunocytochemistry for diagnostic cytopathology-A practical guide

Cytological specimens, which are obtained by minimally invasive methods, are an excellent source of diagnostic material. Sometimes they are the only material available for diagnosis as well as for prognostic/predictive markers. When cytomorphology is not straightforward, ancillary tests may be required for a definitive diagnosis to guide clinical management. Immunocytochemistry (ICC) is the most common and practical ancillary tool used to reach a diagnosis when cytomorphology is equivocal, to differentiate entities with overlapping morphological features, and to determine the cell lineage and the site of origin of a metastatic neoplasm. Numerous immunomarkers are available, and some are expressed in multiple neoplasms. To rule out entities within a differential diagnosis, the use of more than one marker, sometimes panels, is necessary. ICC panels for diagnostic purposes should be customised based on the clinical context and cytomorphology, and the markers should be used judiciously to preserve material for additional tests for targeted therapies in the appropriate setting. This review offers a practical guide for the use of ICC for diagnostic cytopathology, covering the most commonly encountered non-hematolymphoid diagnostic scenarios in various body sites.

Extra-Thyroid Extension Prediction by Ultrasound Quantitative Method Based on Thyroid Capsule Response Evaluation

Background

The aim of this study was to assess the interaction between thyroid malignancies and thyroid anterior capsule by ultrasound quantification to determine extra-capsular invasion.

Material/Methods

A total of 145 patients preoperatively diagnosed with malignant nodules under the thyroid anterior capsule were selected and routinely examined by ultrasound. The length of the nodules (from the junction of the nodule capsule to the deepest point of the nodule, vertical diameter, V) and the distance between the nodule protruding from thyroid capsule and the highest protruding (ledge length, L) nodule were used to obtain the L/V ratio. These parameters where then used to compare the efficacy of predicting extra-thyroid extension (ETE) between L/V, the aspect ratio of the tumor, and manual judgment.

Results

Out of 145 nodules, there were 63 ETEs and 82 non-ETEs determined by ultrasound. Extra-capsular invasion was associated with L//V ratio, but there was no significant correlation between capsular invasion and AR (aspect ratio), age, location, or presence of clustered calcification. The ability of the ratio of L/V to predict extra-capsular invasion was superior to the predictive ability of the AR ratio. With a Youden index of 0.593, the L/V ratio was 0.2325. The use of the L/V ratio to determine the presence of ETE was superior to subjective visual judgment.

Conclusions

The calculation of L/V ratio by ultrasound could more precisely predict the ETE compared with manual judgment, which indirectly reflects the interaction between thyroid capsule and malignant nodules. The above conclusions need to be confirmed by a range of cases.

Risk Stratification Study of Indeterminate Thyroid Nodules with a next-generation Sequencing Assay with Residual ThinPrep® Material

Objective: The management of indeterminate thyroid nodules is challenging. Molecular testing has emerged as a promising method for stratifying this gray area of fine-needle aspiration (FNA) cytology. Next-generation sequencing (NGS) can be used to test a large variety of genetic changes with very small amounts of nucleic acids obtained from FNA samples.

Methods: Thyroid FNA assays were classified according to the Bethesda System for Reporting Thyroid Cytopathology after routine ThinPrep® slide preparation. Indeterminate nodules with surgical outcomes were assayed with an 18-gene NGS panel with the residual ThinPrep® material, including nodules categorized as atypia of undetermined significance (AUS)/follicular lesions of undetermined significance (FLUS) or follicular neoplasm (FN)/suspicious for a follicular neoplasm (SFN). We evaluated the diagnostic efficacy of the 18-gene panel for thyroid malignancies and potential malignancies and compared it with a well-accepted examination, ThyroSeq v2 testing.

Results: A total of 36 indeterminate nodules were assayed, seven were categorized as AUS/FLUS and 29 as FN/SFN. All of them had adequate DNA for the NGS procedure. When noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was considered malignant, the risk of malignancy was 71.4% for AUS/FLUS nodules, and 69.0%for FN/SFN nodules. The 18-gene panel showed 72.0% sensitivity, 72.7% specificity, 85.7% positive predictive value (PPV), and 53.3% negative predictive value (NPV) in identifying malignancies and potential malignancies in the indeterminate nodules. Compared with a multicenter report from ThyroSeq v2 testing, 18-gene panel showed a lower NPV (p=0.005), but a higher PPV (p=0.02).

Conclusions: NGS assays are feasible on residual ThinPrep® material, with the advantage of not requiring additional FNA procedure. The 18-gene panel testing can be used as a 'rule in' test for surgical management based on indeterminate nodules and showed a lower NPV but a higher PPV compared to ThyroSeq v2 testing.

Molecular testing in diagnosis of indeterminate thyroid cytology: Trends and drivers

Fine needle aspiration (FNA), the cornerstone of diagnosis in thyroid swellings, fails to render a definitive diagnosis in about 20% to 30% of cases that are reported as indeterminate on cytology. Since the clinical management in thyroid rests on the risk of malignancy (ROM) in a given nodule, this distinction between "benign" and "possibly malignant" assumes paramount clinical importance. Over the last two decades, tremendous progress has been achieved in our understanding of the molecular basis of thyroid pathologies leading to identification of several genetic alterations that could potentially be exploited for diagnostic, prognostic and therapeutic purposes. An array of molecular tests has hit the markets aiming to predict the ROM in thyroid nodules. A deeper understanding of the strengths and limitations of these tests is imperative to be able to judiciously choose the right molecular test in a given case for maximum clinical benefit. This narrative review provides an overview of current status of molecular testing in the evaluation of thyroid nodules encompassing the current status and applications of these tests in diagnostic, prognostic and therapeutic areas along with a brief insight into the future developments in this field.

High-risk and intermediate-high-risk results from the ThyroSeq v2 and v3 thyroid genomic classifier are associated with neoplasia: Independent performance assessment at an academic institution

BACKGROUND

The ThyroSeq panel tests for genetic alterations to risk-stratify cytologically indeterminate nodules. The authors assessed the test performance of the tests, including the latest version (v3), at an academic center.

METHODS

Results from ThyroSeq testing (v2 and v3) were reviewed over 2 years, and patient demographics, cytology diagnoses, results of ThyroSeq testing, and histopathologic diagnoses on resection (if available) were collected.

RESULTS

One hundred eighty-five nodules were tested from 178 patients, including 94 nodules tested with v2 and 91 nodules tested with v3. Overall, 28 of 185 nodules (15%) yielded a high-risk or intermediate-high-risk mutation (HRM). Of the patients with these nodules, 19 of 25 (76%) had neoplastic nodules, and 11 of 25 (44%) had a malignancy or a noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). Only 16 of 147 nodules (11%) that were negative or had low-risk genetic alterations underwent resection, with 1 false-negative result (a papillary thyroid carcinoma tested with v2). No false-negative results were identified with v3. Two nodules had TP53 mutations identified, both of which were benign on resection. Nodules with HRM that were tested with v2 and v3 had a positive predictive value (PPV) for malignancy of 57% and 39%, respectively, and a PPV for neoplasm of 86% and 72%, respectively. The negative predictive values for v2 and v3 were 92% and 100%, respectively.

CONCLUSIONS

The PPV of an HRM result on ThyroSeq v3 was low for malignancy or NIFTP, and the PPV for neoplasm was higher. RAS-type mutations were the most commonly identified in both benign and malignant nodules. Thyroseq v3 had a lower PPV for both malignancy/NIFTP and neoplasm than v2 but did not produce any false-negative results.

Diagnostic accuracy of molecular testing with three molecular markers on thyroid fine-needle aspiration cytology with abnormal category

BACKGROUND

Cases with abnormal category, determined by thyroid fine-needle aspiration (FNA), frequently undergo surgical resection, despite the majority of cases being identified as benign after resection. Additional diagnostic markers are needed to guide the management of patients with abnormal thyroid nodules.

MATERIALS AND METHODS

The retrospective study enrolled 150 cases diagnosed abnormal by FNA cytology that had undergone molecular testing with three markers (BRAF V600E, NRAS, and KRAS) on the cell block. Seventy-one cases had a surgical follow-up.

RESULTS

When NIFTP is not considered as malignant, positive predictive values (PPVs) of cytology and combined cytology and molecular testing (CC-MT) were 67.6% (95% CI: 0.555-0.782) and 89.2% (95% CI: 0.746-0.970) (P = .004), respectively. The sensitivity of the CC-MT was 68.8%, specificity was 82.5%, and the false-positive rate was 17.4%. When NIFTP is considered as malignant, PPVs of cytology and CC-MT were 83.1% (95% CI: 0.743-0.918) and 94.6% (95% CI: 0.873-1.018) (P = .047), respectively. The sensitivity of the CC-MT was 59.3%, specificity was 83.3%, and the false-positive rate was 16.7%.

CONCLUSION

The addition of molecular testing with a small panel to FNA cytology may increase the PPV of cytology in abnormal categories. Small panel (BRAF V600E, KRAS, and NRAS) with high specificity and high PPVs may be used particularly for the detection of thyroid malignancy. Cell blocks can be an especially useful and straightforward method for molecular diagnostic studies.

Performance of a Genomic Sequencing Classifier for the Preoperative Diagnosis of Cytologically Indeterminate Thyroid Nodules

Importance

Use of next-generation sequencing of RNA and machine learning algorithms can classify the risk of malignancy in cytologically indeterminate thyroid nodules to limit unnecessary diagnostic surgery.

Objective

To measure the performance of a genomic sequencing classifier for cytologically indeterminate thyroid nodules.

Design, Setting, and Participants

A blinded validation study was conducted on a set of cytologically indeterminate thyroid nodules collected by fine-needle aspiration biopsy between June 2009 and December 2010 from 49 academic and community centers in the United States. All patients underwent surgery without genomic information and were assigned a histopathology diagnosis by an expert panel blinded to all genomic information. There were 210 potentially eligible thyroid biopsy samples with Bethesda III or IV indeterminate cytopathology that constituted a cohort previously used to validate the gene expression classifier. Of these, 191 samples (91.0%) had adequate residual RNA for validation of the genomic sequencing classifier. Algorithm development and independent validation occurred between August 2016 and May 2017.

Exposures

Thyroid nodule surgical histopathology diagnosis by an expert panel blinded to all genomic data.

Main Outcomes and Measures

The primary end point was measurement of genomic sequencing classifier sensitivity, specificity, and negative and positive predictive values in biopsies from Bethesda III and IV nodules. The secondary end point was measurement of classifier performance in biopsies from Bethesda II, V, and VI nodules.

Results

Of the 183 included patients, 142 (77.6%) were women, and the mean (range) age was 51.7 (22.0-85.0) years. The genomic sequencing classifier had a sensitivity of 91% (95% CI, 79-98) and a specificity of 68% (95% CI, 60-76). At 24% cancer prevalence, the negative predictive value was 96% (95% CI, 90-99) and the positive predictive value was 47% (95% CI, 36-58).

Conclusions and Relevance

The genomic sequencing classifier demonstrates high sensitivity and accuracy for identifying benign nodules. Its 36% increase in specificity compared with the gene expression classifier potentially increases the number of patients with benign nodules who can safely avoid unnecessary diagnostic surgery.

The impact of non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) on the diagnosis of thyroid nodules

More than 70 years ago, Prof. Pierre Masson, a renowned French-Canadian pathologist (1880-1959), advised us that "No classification is more difficult to establish than that of thyroid carcinomas…Of all cancers, they teach, perhaps, the greatest lessons of humility to histopathologists." Almost 70 years later, the recent evidence-based reclassification of the non-invasive encapsulated follicular variant of papillary thyroid carcinoma (FVPTC) as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), has demonstrated that this problematic is still ongoing. For about 30 years, it was wrongly assumed that the encapsulated FVPTC behaved and spread like its classical counterpart and, therefore, that it should be treated likewise. As such, the renaming of a malignant entity as a nonmalignant (albeit not benign) neoplasm has contributed to optimizing patient care by deescalating treatment and follow-up for an indolent neoplasm, decreasing medical expense and complications possibly caused by further treatment including radioactive iodine, and reassuring patients with this diagnosis. At the same time, NIFTP has significant implications not only for the practice of thyroid cytopathology but also for surgical pathology and for molecular tests, creating significant new challenges. NIFTP has rigorous histopathologic diagnostic criteria, including papillary-like nuclear features, and submission of the entire tumor capsule and content is required to exclude both invasion and presence of papillary structures. Cytologically, because of the morphological overlap with other follicular neoplasms and with papillary thyroid carcinoma (PTC), most NIFTP are diagnosed into one of the indeterminate Bethesda categories (III-V) and can be adequately triaged for surgery. From a molecular view, NIFTP are most often characterized by RAS-type mutations, similar to other follicular-patterned lesions, and molecular testing can be helpful to suggest NIFTP preoperatively. In this review, we focus on the impact of NIFTP on the diagnosis of thyroid nodules.

Educational Case: Cytology for Staging Neoplasia and Thyroid Neoplasms

The following fictional case is intended as a learning tool within the Pathology Competencies for Medical Education (PCME), a set of national standards for teaching pathology. These are divided into three basic competencies: Disease Mechanisms and Processes, Organ System Pathology, and Diagnostic Medicine and Therapeutic Pathology. For additional information, and a full list of learning objectives for all three competencies, seehttp://journals.sagepub.com/doi/10.1177/2374289517715040.

GDNF and the RET Receptor in Cancer: New Insights and Therapeutic Potential

The Glial cell line-derived neurotrophic Family Ligands (GFL) are soluble neurotrophic factors that are required for development of multiple human tissues, but which are also important contributors to human cancers. GFL signaling occurs through the transmembrane RET receptor tyrosine kinase, a well-characterized oncogene. GFL-independent RET activation, through rearrangement or point mutations occurs in thyroid and lung cancers. However, GFL-mediated activation of wildtype RET is an increasingly recognized mechanism promoting tumor growth and dissemination of a much broader group of cancers. RET and GFL expression have been implicated in metastasis or invasion in diverse human cancers including breast, pancreatic, and prostate tumors, where they are linked to poorer patient prognosis. In addition to directly inducing tumor growth in these diseases, GFL-RET signaling promotes changes in the tumor microenvironment that alter the surrounding stroma and cellular composition to enhance tumor invasion and metastasis. As such, GFL RET signaling is an important target for novel therapeutic approaches to limit tumor growth and spread and improve disease outcomes.

Determining the molecular test for indeterminate thyroid nodules best suited for our practice: A quality assurance study

INTRODUCTION

Currently, molecular studies are widely used as a guiding tool in further management of cytologically indeterminate thyroid nodules. At our institution, clinicians have recently expressed concern over receiving "less positive molecular results" upon switching from an extended 14 gene mutation panel (EGMP) to a 7 gene mutation panel (GMP). Our goal is to compare outcomes of these two tests in regards to the performance characteristics and clinical impact.

MATERIALS AND METHODS

All thyroid fine-needle aspiration (FNA) biopsy specimens sent for molecular studies from 2016 to 2017 were retrospectively studied. Cytopathology diagnosis, pertinent clinical findings, molecular results, and follow-up (F/U) surgical and cytology diagnoses were recorded.

RESULTS

Of the total 165 cases sent for molecular tests 86 (52%) were GMP and 79 (47%) EGMP. There were 21 (24%) and 40 (50%) cases with positive GMP and EGMP results, respectively. Within these positive cases (n = 61), there were a total of 33 (54%) patients who underwent surgical resection and 28 (45%) patients had no follow-up. The molecular findings and surgical pathologic diagnoses obtained are illustrated in Figures 1 through 4 for GMP and EGMP, respectively.

CONCLUSIONS

The selection of molecular testing should be directed toward optimizing patient care and facilitate clinical management. This quality assurance study helped in understanding the complexities associated with test selection best suited for our institution and in educating clinicians.

Cytomorphologic, Imaging, Molecular Findings, and Outcome in Thyroid Follicular Lesion of Undetermined Significance/Atypical Cell of Undetermined Significance (AUS/FLUS): A Mini-Review

OBJECTIVES

Since the introduction of the entity of "Atypical cell of undetermined significance /follicular lesion of undetermined significance" (AUS/FLUS) by The Bethesda System for Reporting Thyroid Cytology (TBSRTC) in 2007, there have been many published studies about the cytomorphologic criteria, subclassification, outcome, and management of patients with the diagnosis of AUS/FLUS. There have been many studies in different aspects of this indeterminate category, i.e., cytologic and molecular findings, ultrasonographic findings, and in some instances even core-needle biopsy to address a better and safer way of the management of patients with this fine-needle aspiration cytology diagnosis. The second edition of TBSRTC and the 2015 American Thyroid Association guidelines provide an update on the follow-up and management of AUS/FLUS. A multidisciplinary team consisting of pathologists, endocrinologists, surgeons, and radiologists should be involved in the diagnosis and management of AUS/FLUS, and all of them should be aware of the heterogeneity of this lesion for the prediction of the treatment and outcome.

STUDY DESIGN

In this review, we consider different research platforms (2008-2017) to find the best and key reports for the above-mentioned challenging aspects of AUS/FLUS.

CONCLUSION

AUS/FLUS is now a well-defined group of thyroid lesions, which can be most accurately diagnosed and managed with cytomorphology, molecular, and ancillary studies.

Current controversies and future directions in the diagnosis and management of differentiated thyroid cancers

Despite the development of novel diagnostic, surgical, and chemotherapeutic approaches to differentiated thyroid cancers (DTCs), the diagnosis and management of these tumors remains controversial. The most recent American Thyroid Association (ATA) guidelines, released in 2015, reflect a recent shift towards less aggressive management for patients with DTCs. However, many clinicians have expressed concern that more conservative management will put patients at risk for disease recurrence and metastasis. In particular, the management of indeterminate nodules on fine needle aspiration (with special attention to genetic and epigenetic markers of malignancy), the extent of surgery for known differentiated cancers, the role of adjuvant radioactive iodine (RAI) therapy, and novel targeted treatments with tyrosine kinase inhibitors (TKIs) represent current areas of uncertainty and opportunities for future research. In this review, we examine the current state of the art in these areas, and address some of the questions that remain.

Utilization of direct smears of thyroid fine-needle aspirates for ancillary molecular testing: A comparison of two proprietary testing platforms

BACKGROUND

Ancillary molecular testing has been recommended for thyroid fine-needle aspirates (FNA) with indeterminate cytologic diagnoses. Rosetta Genomics and Interpace Diagnostics have developed assays that can utilize direct smears as the testing substrate.

METHODS

A retrospective study of indeterminate thyroid FNAs with known histologic follow-up was performed. One Diff-Quik-stained smear and one Papanicolaou-stained smear with similar cellularity (at least 60-100 lesional cells) from each case were sent to Rosetta and Interpace, respectively, for analysis. The results were directly compared and correlated with the final histopathology. Neither company was aware of the follow-up histologic findings in these cases.

RESULTS

A total of 10 thyroid FNAs were identified from our 2015 files. The cytologic diagnoses included follicular lesion of undetermined significance (FLUS, n = 5), follicular neoplasm/suspicious for follicular neoplasm (FN/SFN, n = 4), and suspicious for malignancy (SM, n = 1). Of the seven cases with benign histology, six smears were classified as benign by the RosettaGX microRNA classifier, and one case was designated as suspicious. Five cases were negative by both ThyGenX oncogene panel and ThyraMIR microRNA classifier. One case was negative by ThyGenX and positive on follow-up ThyraMIR, and one case was positive for KRAS mutation and positive on ThyraMIR. Both the RosettaGX and ThyGenX/ThyraMIR tests demonstrated positive results for the three histologically malignant cases.

CONCLUSION

This study demonstrates that two molecular testing platforms performed equally well using our stained direct smears. Both molecular tests revealed a 100% negative predictive rate. RosettaGX showed a 75% positive predictive value in comparison to 60% for ThyGenX/ThyraMIR.