Thyroid Nodule Diagnostic Markers in the Face of the New NIFTP Category: Time for a Reset?

Malignancy Risk of Follicular Neoplasm (Bethesda IV) With Variable Cutoffs of Tumor Size: A Systemic Review and Meta-Analysis

CONTEXT

The decision on diagnostic lobectomy for follicular neoplasms (FN) is challenging.

OBJECTIVE

This meta-analysis investigates whether an appropriate size cutoff exists for recommending surgery for thyroid nodules diagnosed as FN by fine needle aspiration.

METHODS

The Ovid-Medline, EMBASE, Cochrane, and KoreaMed databases were searched for studies reporting the malignancy rate of FN/suspicious for FN (FN/SFN) according to tumor size, using search terms "fine needle aspiration," "follicular neoplasm," "lobectomy," "surgery," and "thyroidectomy."

RESULTS

Fourteen observational studies comprising 2016 FN/SFN nodules with postsurgical pathologic reports were included, and 2 studies included malignancy rates with various tumor sizes. The pooled malignancy risk of FN/SFN nodules according to size was: odds ratio (OR) 2.29 (95% CI, 1.68-3.11) with cutoff of 4 cm (9 studies), OR 2.39 (95% CI, 1.45-3.95) with cutoff of 3 cm (3 studies), and OR 1.81 (95% CI, 0.94-3.50) with cutoff of 2 cm (5 studies). However, tumors ≥2 cm also showed a higher risk (OR 2.43; 95% CI, 1.54-3.82) based on the leave-one-out meta-analysis after removal of 1 influence study. When each cutoff size was evaluated by summary receiver operating characteristic (sROC) curves, the cutoff of 4 cm showed the highest summary area under the curve (sAUC, 0.645) compared to other cutoffs (sAUC, 0.58 with 2 cm, and 0.62 with 3 cm), although there was no significant difference.

CONCLUSION

Although the risk of malignancy increases with increasing tumor size, the risk remains significant at all tumor sizes and no cutoff limit can be recommended as a decision-making parameter for diagnostic surgery in Bethesda IV thyroid nodules.

A retrospective analysis of molecular testing in cytologically indeterminate thyroid nodules with histologic correlation: Experience at a heterogenous multihospital system

INTRODUCTION

Thyroid malignancy is one of the most common types of cancer in developed nations. Currently, fine-needle aspiration cytology (FNAC) is the most practical screening test for thyroid nodules. However, cytologically indeterminate samples comprise approximately 15%-30% of cases. These include cases classified as atypia of undetermined significance (AUS), follicular neoplasm (FN), and suspicious for malignancy (SFM). Indeterminate cases can be sent for molecular testing for more definitive classification to help guide management and prevent overtreatment of benign thyroid nodules. We conducted a retrospective review on molecular testing of indeterminate thyroid FNAC and reviewed subsequent histologic diagnoses in resection specimens to assess how molecular testing supported a diagnosis and its effect on clinical management of patients at our institution.

METHODS

A retrospective chart review was performed on all thyroid FNAC specimens, corresponding molecular testing, and subsequent surgical resection specimens over a 6-year period.

RESULTS

A total of 10,253 thyroid FNAC were performed in our hospital system during our study period, of which 10% (n = 1102/10,253) had indeterminate FNAC results. Molecular testing was performed in 16% (n = 178/1102) of indeterminate cytology cases. Genetic alterations were identified in 39% (n = 69/178) of the cases sent for molecular testing. The majority of cytologically indeterminate cases sent for molecular testing were follicular-patterned lesions and their corresponding resection specimens revealed mostly low grade follicular derived neoplasms (i.e., follicular adenoma, non-invasive follicular thyroid neoplasm with papillary-like nuclear features, and follicular variant of papillary thyroid carcinoma). Of the cases with identified genetic alterations, 75% (n = 52/69) were treated surgically. In cases with no genetic alterations identified, only 18% (n = 20/109) were treated surgically.

DISCUSSION/CONCLUSION

Molecular testing on cytologically indeterminate thyroid nodules can help provide a more accurate risk of malignancy assessment in patients with lesions that are difficult to diagnosis based solely on FNAC morphology. The types of genetic alterations identified in the resected thyroid lesions were consistent with what has been previously described in the literature. Additionally, we found that in the patients with indeterminate thyroid FNAC with adjunct molecular testing, more than half did not undergo surgical resection. This finding emphasizes the value of adding molecular testing in patients, particularly when attempting to reduce unnecessary surgical intervention.

An update on the management of thyroid nodules: rationalising the guidelines

BACKGROUND

Guidance for the management of thyroid nodules has evolved over time, from initial evaluation based predominantly on clinical grounds to now including the established role of ultrasound and fine needle aspiration cytology in their assessment. There is, however, significant variation in the management of thyroid nodules depending on which national guidelines are followed. In addition, there are certain clinical situations such as pregnancy and paediatric thyroid nodules that have differing evaluation priorities.

OBJECTIVES

This review aimed to provide an overview of currently accepted practices for the initial investigation and subsequent management of patients with thyroid nodules for the non-specialist. The review also addresses areas of variance between the systems in common clinical use, as well as newer, evolving technologies, including molecular testing in the evaluation of malignancy in thyroid nodules.

Retrospective analysis of cancer-specific gene expression panel for thyroid fine needle aspiration specimens

BACKGROUND

While molecular testing is a promising strategy for preoperative assessment of cytologically indeterminate thyroid nodules, thyroid fine needle aspiration biopsy (FNA) presents unique challenges for molecular assays, including contaminating peripheral blood mononuclear cells (PBMC) and variable numbers of evaluable epithelial thyroid cells. Moreover, the newly recognized entity, noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), has added an additional challenge to the currently available molecular diagnostic platforms. New diagnostic tools are still needed to correctly distinguish benign and malignant thyroid nodules preoperatively.

METHODS

Twenty-two transcript splice variants from 12 genes we previously identified as discriminating benign from malignant thyroid nodules were characterized in 80 frozen thyroid tumors from 8 histological subtypes. Isoforms detectable in PBMC were excluded, and the 5 most discriminating isoforms were further validated by real-time quantitative PCR (qPCR) on intraoperative FNA samples from 59 malignant tumors, 55 benign nodules, and 23 NIFTP samples. The qPCR threshold cycle values for each transcript were normalized to the thyrocyte-specific thyroid peroxidase isoform 1 (TPO1) and z-transformed. Receiver operating characteristic (ROC) analyses of the composite transcript scores were used to evaluate classification of thyroid FNAs by the 5-gene isoform expression panel.

RESULTS

A molecular signature was developed by combining expression levels of specific isoforms of CDH3, FNDC4, HMGA2, KLK7, and PLAG1. FNAs containing at least 12-36 thyrocytes were sufficient for this assay. The 5-gene composite score achieved an area under the ROC curve (AUC) of 0.86 for distinguishing malignant from benign nodules, with a specificity of 91%, sensitivity of 75%, negative predictive value of 91%, and positive predictive value of 74%.

CONCLUSION

Our newly developed 5-gene isoform expression panel distinguishes benign from malignant thyroid tumors and, may help distinguish benign from malignant thyroid nodules in the context of the new NIFTP subtype.

Thyroseq v3, Afirma GSC, and microRNA Panels Versus Previous Molecular Tests in the Preoperative Diagnosis of Indeterminate Thyroid Nodules: A Systematic Review and Meta-Analysis

BACKGROUND

Molecular tests are being used increasingly as an auxiliary diagnostic tool so as to avoid a diagnostic surgery approach for cytologically indeterminate thyroid nodules (ITNs). Previous test versions, Thyroseq v2 and Afirma Gene Expression Classifier (GEC), have proven shortcomings in malignancy detection performance.

OBJECTIVE

This study aimed to evaluate the diagnostic performance of the established Thyroseq v3, Afirma Gene Sequencing Classifier (GSC), and microRNA-based assays versus prior iterations in ITNs, in light of "rule-in" and "rule-out" concepts. It further analyzed the impact of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) reclassification and Bethesda cytological subtypes on the performance of molecular tests.

METHODS

Pubmed, Scopus, and Web of Science were the databases used for the present research, a process that lasted until September 2020. A random-effects bivariate model was used to estimate the summary sensitivity, specificity, positive (PLR) and negative likelihood ratios (NLR), and area under the curve (AUC) for each panel. The conducted sensitivity analyses addressed different Bethesda categories and NIFTP thresholds.

RESULTS

A total of 40 eligible studies were included with 7,831 ITNs from 7,565 patients. Thyroseq v3 showed the best overall performance (AUC 0.95; 95% confidence interval: 0.93-0.97), followed by Afirma GSC (AUC 0.90; 0.87-0.92) and Thyroseq v2 (AUC 0.88; 0.85-0.90). In terms of "rule-out" abilities Thyroseq v3 (NLR 0.02; 95%CI: 0.0-2.69) surpassed Afirma GEC (NLR 0.18; 95%CI: 0.10-0.33). Thyroseq v2 (PLR 3.5; 95%CI: 2.2-5.5) and Thyroseq v3 (PLR 2.8; 95%CI: 1.2-6.3) achieved superior "rule-in" properties compared to Afirma GSC (PLR 1.9; 95%CI: 1.3-2.8). Evidence for Thyroseq v3 seems to have higher quality, notwithstanding the paucity of studies. Both Afirma GEC and Thyroseq v2 performance have been affected by NIFTP reclassification. ThyGenNEXT/ThyraMIR and RosettaGX show prominent preliminary results.

CONCLUSION

The newly emerged tests, Thyroseq v3 and Afirma GSC, designed for a "rule-in" purpose, have been proved to outperform in abilities to rule out malignancy, thus surpassing previous tests no longer available, Thyroseq 2 and Afirma GEC. However, Thyroseq v2 still ranks as the best rule-in molecular test.

SYSTEMATIC REVIEW REGISTRATION

http://www.crd.york.ac.uk/PROSPERO, identifier CRD42020212531.

Molecular trait of follicular-patterned thyroid neoplasms defined by MALDI-imaging

In the field of thyroid neoplasms, the most interesting recent change regards the introduction of a new terminology for follicular-patterned thyroid tumors, named Noninvasive Thyroid Neoplasm with Papillary-like Nuclear Features (NIFTP). This pre-malignant tumor is considered to be the putative precursor of invasive carcinoma. However, given that several issues are still unresolved, the application of ancillary tools, based on omics-techniques, may improve the clinical management of these challenging cases. The present paper highlights the proteomic profiles of a series of NIFTPs submitted to Fine Needle Aspirations (FNAs) and analysed by MALDI-imaging in order to confirm the heterogeneous phenotype of nodules included in the present NIFTP terminology and to underline the necessity of more accurate biomarkers that can be used for their characterization. Ethical and economic implications in terms of healthcare costs, operative risks, morbidity, as well as the potential need for lifelong hormone replacement therapy, seem to be significant reasons to approach the characterization of NIFTPs using alternative tools such as MALDI-MSI.

Thyroid Nodule Molecular Testing: Is It Ready for Prime Time?

Cytologically indeterminate thyroid nodules remain a diagnostic and clinical challenge, and molecular testing has been advocated and advanced as a diagnostic modality to help guide treatment. While studies have expounded on the improved diagnostic certainty with these tests, data demonstrating meaningful clinical impact and supporting their routine use is still limited at best. In this review, we discuss the limitations regarding diagnostic accuracy, impact on surgical decision-making and outcomes, and cost-effectiveness of molecular testing. By highlighting the limitations of these tests, we aim to promote more thoughtful utilization of these tools in the management of thyroid nodules going forward.

Treatment of Differentiated Thyroid Carcinomas

Differentiated thyroid cancer (DTC) is the most common thyroid cancer and is frequently encountered in clinical practice. The incidence of DTC has increased significantly over the past three decades. Surgical resection, radioactive iodine (RAI), and levothyroxine suppression therapy remain the primary modalities for DTC treatment. Active surveillance for low-risk thyroid cancer may be an alternative to immediate surgery for appropriately selected patients. Patient characteristics influence treatment selection and intensity. In the subset of patients with progressive distant metastatic disease, not amenable to treatment with surgery or RAI, novel agents, including targeted therapies and immunotherapy, should be considered.

Revised criteria for diagnosis of NIFTP reveals a better correlation with tumor biological behavior

The recent reclassification of a follicular variant of papillary thyroid carcinoma (FVPTC), subset as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), aims to avoid overtreatment of patients with an indolent lesion. The diagnosis of NIFTP has recently been revisited using more rigid criteria. This study presents histological and molecular findings and a long clinical follow-up of 94 FVPTC, 40 cases of follicular adenoma (FTA) and 22 cases of follicular carcinoma (FTC) that were classified before the advent of the NIFTP reclassification. All slides were reviewed using these rigid criteria and analysis of numerous sections of paraffin blocks and reclassified as 7 NIFTPs, 2 EFVPTCs, 29 infiltrative FVPTC (IFVPTCs), 57 invasive EFVPTC (I-EFVPTCs), 39 FTAs and 22 FTCs. Remarkably, EFVPTC and NIFTP patients were all free of disease at the end of follow-up and showed no BRAF mutation. Only one NIFTP sample harbored mutations, an NRAS Q61R. PAX8/PPARG fusion was found in I-EFVPTCs and FTC. Although additional studies are needed to identify a specific molecular profile to aid in the diagnosis of lesions with borderline morphological characteristics, we confirmed that the BRAF V600E mutation is an important tool to exclude the diagnosis of NIFTP. We also show that rigorous histopathological criteria should be strongly followed to avoid missing lesions in which more aggressive behavior is present, mainly via the analysis of capsule or vascular invasion and the presence of papillary structures.

Comparison of Postmarketing Findings vs the Initial Clinical Validation Findings of a Thyroid Nodule Gene Expression Classifier: A Systematic Review and Meta-analysis

Importance

In the United States, the most used molecular test for the evaluation of cytologically indeterminate thyroid nodules is the Afirma gene expression classifier (GEC).

Objective

To evaluate the GEC's diagnostic performance through a novel approach to assess whether the findings of the initial validation study are consistent with the results of postmarketing studies.

Data Sources

PubMed was systematically searched from inception through October 26, 2017, using the terms gene expression classifier or Afirma or GEC and thyroid.

Study Selection

Studies included were those in which the GEC diagnostic performance could be calculated on consecutively resected cytologically indeterminate thyroid nodules.

Data Extraction and Synthesis

Two observers independently assessed study eligibility and risk of bias using the quality assessment tool for observational cohort and cross-sectional studies of the National Heart, Lung, and Blood Institute. Summary data were extracted by a reviewer and reviewed independently by another. Study authors were contacted if missing data were needed. Data were pooled using a random-effects model. PRISMA and MOOSE guidelines were followed.

Main Outcomes and Measures

Evaluation of the linear correlation between the benign call rate (BCR) and the positive predictive value (PPV).

Results

Of the 137 retrieved titles, 19 (13.9%) were included, comprising a total of 2568 thyroid nodules. Based on a simulation using the sensitivity and specificity reported in the initial validation study, the observed BCR and PPV values in postmarketing studies would have to be explained by different underlying prevalence rates of cancer (15% vs 30%), which is an impossible event. Furthermore, the overall correlation between BCR and PPV for independent studies fell outside the PPV 95% CI of the initial validation study (95% CI, 0.17-0.32) at the BCR of pooled independent studies (0.45) and was just at the limit of the BCR 95% CI of the initial validation study (95% CI, 0.32-0.45) at the PPV of pooled independent studies (0.45). The diagnostic performance was statistically significantly better for atypia or follicular lesions of undetermined significance (diagnostic odds ratio [DOR], 5.67; 95% CI, 4.23-7.60) compared with follicular neoplasms (DOR, 2.24; 95% CI, 1.45-3.47).

Conclusions and Relevance

The findings suggest that the initial validation study cohort was not representative of the populations in whom the GEC has been used, calling into question its reported diagnostic performance, including its negative predictive value.

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.

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP): a review for clinicians

Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is an encapsulated or clearly delimited, noninvasive neoplasm with a follicular growth pattern and nuclear features of papillary thyroid carcinoma (PTC). It is considered a 'pre-malignant' lesion of the RAS-like group. Ultrasonography (US), cytology and molecular tests are useful to suspect thyroid nodules that correspond to NIFTP but there is wide overlap of the results with the encapsulated follicular variant of PTC (E-FVPTC). In these nodules that possibly or likely correspond to NIFTP, if surgery is indicated, lobectomy is favored over total thyroidectomy. The diagnosis of NIFTP is made after complete resection of the lesion by observing well-defined criteria. In the case of patients who received the diagnosis of FVPTC and whose pathology report does not show findings of malignancy (lymph node metastasis, extrathyroidal invasion, vascular/capsular invasion), if the tumor was encapsulated or well delimited, the slides can be revised by an experienced pathologist to determine whether the diagnostic criteria of NIFTP are met, but special attention must be paid to the adequate representativeness of the capsule and tumor. Since NIFTP is not 'malignant', tumor staging is not necessary and patients are not submitted to thyroid cancer protocols or guidelines. We believe that patients with NIFTP without associated malignancy and without nodules detected by US of the remnant lobe (if submitted to lobectomy) can be managed like those with follicular adenoma.

Role of Ancillary Techniques in Thyroid Cytology Specimens

Ancillary molecular testing has emerged as a promising way to refine the preoperative risk stratification of thyroid nodules with indeterminate fine needle aspiration (FNA) biopsy results. Commercially available molecular tests for thyroid FNAs include those that analyze samples for mutations and gene fusions, gene expression alterations, microRNA expression alterations, chromosomal copy number alterations, or a combination thereof. This review summarizes the performance characteristics of the most current iterations of three tests currently marketed for cytologically indeterminate thyroid nodules: ThyroSeq v3, ThyGeNEXT/ThyraMIR, and Afirma Gene Sequencing Classifier.

Updates in Thyroid Cytology

Genomic, clinical, and pathologic studies have prompted a more risk-stratified approach to the management of patients with thyroid nodules. The recent nomenclature change concerning noninvasive follicular thyroid neoplasm with papillary-like nuclear features reflects the clinical trend toward conservative treatment choices for carefully selected low-risk thyroid neoplasms. These developments have occurred in parallel with a growing array of molecular tests intended to improve clinical triage for patients with indeterminate fine needle aspiration diagnoses. This review discusses the implications of the nomenclature revision on the interpretation of thyroid fine needle aspiration and updates available ancillary molecular tests for thyroid fine needle aspirations.

Papillary Thyroid Microcarcinoma: Reclassification to Non-Invasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP): a Retrospective Clinicopathologic Study

Papillary thyroid microcarcinoma (PTMC) accounts for nearly 50% of newly diagnosed PTC cases. There is considerable debate in literature about the clinicopathologic features and prognostic significance of PTMC and whether it should be treated as a separate entity. Due to lack of agreement and supportive data, the consensus study group that established the criteria for non-invasive thyroid neoplasm with papillary-like features (NIFTP) kept its size above 1 cm i.e., excluding PTMC from this new group. As a result, to date, some patients diagnosed with PTMC get aggressive treatments such as partial or total thyroidectomy and even radioactive iodine ablation. We retrospectively studied clinicopathologic features and long-term follow-up of 48 cases of papillary thyroid microcarcinoma. Of these, 7 cases (15%) had capsular invasion, 2 cases (4%) had extrathyroidal extension, 1 case (2%) had lymphovascular invasion, 5 cases (25%) had lymph node metastases, no case (0%) had any distant metastases, and 1 case had recurrence after long-term follow-up (mean 13.7 years, range 1-21 years). Upon slide review, 8 cases fulfilled the criteria for NIFTP and were sub-classified under this new category. These 8 cases had no recurrence after long-term follow-up (mean 12.1 years, range 7-19 years). In this study, we confirmed the previous published reports exhibiting indolent nature of PTMC and also suggested that PTMC cases that fulfill all the criteria for NIFTP can be sub-classified under this term in order to avoid unnecessary aggressive treatment.

Thyroid surgery for differentiated thyroid cancer - recent advances and future directions

Population-based studies have demonstrated that an increasing number of incidental thyroid nodules are being identified. The corresponding increase in thyroid-based diagnostic procedures, such as fine-needle aspiration biopsy, has in part led to an increase in the diagnoses of thyroid cancers and to more thyroid surgeries being performed. Small papillary thyroid cancers account for most of this increase in diagnoses. These cancers are considered to be low risk because of the excellent patient outcomes, with a 5-year disease-specific survival of >98%. As a result, controversy remains regarding the optimal management of newly diagnosed differentiated thyroid cancer, as the complications related to thyroidectomy (primarily recurrent laryngeal nerve injury and hypoparathyroidism) have considerable effects on patient quality of life. This Review highlights current debates, including undertaking active surveillance versus thyroid surgery for papillary thyroid microcarcinoma, the extent of thyroid surgery and lymphadenectomy for low-risk differentiated thyroid cancer, and the use of molecular testing to guide decision-making about whether surgery is required and the extent of the initial operation. This Review includes a discussion of current consensus guideline recommendations regarding these topics in patients with differentiated thyroid cancer. Additionally, innovative thyroidectomy techniques (including robotic and transoral approaches) are discussed, with an emphasis on patient preferences around decision-making and outcomes following thyroidectomy.

Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features in Asian Practice: Perspectives for Surgical Pathology and Cytopathology

The introduction of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was initiated and promoted by pathologists. Recent Asian studies added new knowledge to the existing literature to aid a better understanding of NIFTP. Our original data and the results of a meta-analysis suggest that the initial rate of NIFTP has been overestimated, averaging 9.1% (95% confidence interval [CI] 6.0-12.7%) of all papillary thyroid cancers worldwide. The incidence of NIFTP in the Asian population (1.6%, 95% CI 0.9-2.5%; 7 studies) is significantly lower than that reported in the non-Asian series (13.3%, 95% CI 9.0-18.3%; 18 studies). Such difference could be attributed to various perceptions of histological diagnostic thresholds, different nature of papillary thyroid carcinoma, and different approaches in the management of thyroid nodules. The active surveillance for indeterminate nodules and NIFTP, largely represented in the indeterminate cytologic categories, promoted by Japanese institutions establishes a new paradigm to reduce overtreatment of these patients. The lower prevalence of NIFTP in the Asian series indicates a low impact on the risk of malignancy in cytopathology, as it was demonstrated in our original multi-institutional cohort of thyroid nodules, and may predict a low impact on the performance of commercial molecular tests. Several Korean studies addressed the issue of BRAF mutation in NIFTP, which prompted the current refinement of the diagnostic criteria for NIFTP. Our survey of Asian pathologists found that the term NIFTP has not been universally adopted in the local practice. Endocrine pathologists must promote the new entity through provision of educational activities.

Gene Expression Classifier vs Targeted Next-Generation Sequencing in the Management of Indeterminate Thyroid Nodules

CONTEXT

Molecular testing has reduced the need for diagnostic hemithyroidectomy for indeterminate thyroid nodules. No studies have directly compared molecular testing techniques.

OBJECTIVE

Compare the diagnostic performance of Afirma Gene Expression Classifier (GEC) with that of ThyroSeq v2 next-generation sequencing assay.

DESIGN

Parallel randomized trial, monthly block randomization of patients with Bethesda III/IV cytology to GEC or ThyroSeq v2.

SETTING

University of California, Los Angeles.

PARTICIPANTS

Patients who underwent thyroid biopsy (April 2016 to June 2017).

INTERVENTION

Testing with GEC or ThyroSeq v2.

MAIN OUTCOME MEASURE

Molecular test performance.

RESULTS

Of 1372 thyroid nodules, 176 (13%) had indeterminate cytology and 149 of 157 eligible indeterminate nodules (95%) were included in the study. Of nodules tested with GEC, 49% were suspicious, 43% were benign, and 9% were insufficient. Of nodules tested with ThyroSeq v2, 19% were mutation positive, 77% were mutation negative, and 4% were insufficient. The specificities of GEC and ThyroSeq v2 were 66% and 91%, respectively (P = 0.002); the positive predictive values of GEC and ThyroSeq v2 were 39% and 57%, respectively. Diagnostic hemithyroidectomy was avoided in 28 patients tested with GEC (39%) and 49 patients tested with ThyroSeq v2 (62%). Surveillance ultrasonography was available for 46 nodules (45 remained stable).

CONCLUSIONS

ThyroSeq v2 had higher specificity than Afirma GEC and allowed more patients to avoid surgery. Long-term surveillance is necessary to assess the false-negative rate of these particular molecular tests. Further studies are required for comparison with other available molecular diagnostics and for newer tests as they are developed.

Preoperative Molecular Markers in Thyroid Nodules

The need for distinguishing benign from malignant thyroid nodules has led to the pursuit of differentiating molecular markers. The most common molecular tests in clinical use are Afirma^® Gene Expression Classifier (GEC) and Thyroseq^® V2. Despite the rapidly developing field of molecular markers, several limitations exist. These challenges include the recent introduction of the histopathological diagnosis "Non-Invasive Follicular Thyroid neoplasm with Papillary-like nuclear features", the correlation of genetic mutations within both benign and malignant pathologic diagnoses, the lack of follow-up of molecular marker negative nodules, and the cost-effectiveness of molecular markers. In this manuscript, we review the current published literature surrounding the diagnostic value of Afirma^® GEC and Thyroseq^® V2. Among Afirma^® GEC studies, sensitivity (Se), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV) ranged from 75 to 100%, 5 to 53%, 13 to 100%, and 20 to 100%, respectively. Among Thyroseq^® V2 studies, Se, Sp, PPV, and NPV ranged from 40 to 100%, 56 to 93%, 13 to 90%, and 48 to 97%, respectively. We also discuss current challenges to Afirma^® GEC and Thyroseq^® V2 utility and clinical application, and preview the future directions of these rapidly developing technologies.