Analytical and clinical validation of pairwise microRNA expression analysis to identify medullary thyroid cancer in thyroid fine-needle aspiration samples

Cytologic risk stratification of medullary thyroid carcinoma: Does it make the grade?

Recent efforts to develop a histologic grading system for medullary thyroid carcinoma is gaining broad acceptance. How well do these grading parameters translate to cytology specimens?

New biomarkers: prospect for diagnosis and monitoring of thyroid disease

After the metabolic syndrome and its components, thyroid disorders represent the most common endocrine disorders, with increasing prevalence in the last two decades. Thyroid dysfunctions are distinguished by hyperthyroidism, hypothyroidism, or inflammation (thyroiditis) of the thyroid gland, in addition to the presence of thyroid nodules that can be benign or malignant. Thyroid cancer is typically detected via an ultrasound (US)-guided fine-needle aspiration biopsy (FNAB) and cytological examination of the specimen. This approach has significant limitations due to the small sample size and inability to characterize follicular lesions adequately. Due to the rapid advancement of high-throughput molecular biology techniques, it is now possible to identify new biomarkers for thyroid neoplasms that can supplement traditional imaging modalities in postoperative surveillance and aid in the preoperative cytology examination of indeterminate or follicular lesions. Here, we review current knowledge regarding biomarkers that have been reliable in detecting thyroid neoplasms, making them valuable tools for assessing the efficacy of surgical procedures or adjunctive treatment after surgery. We are particularly interested in providing an up-to-date and systematic review of emerging biomarkers, such as mRNA and non-coding RNAs, that can potentially detect thyroid neoplasms in clinical settings. We discuss evidence for miRNA, lncRNA and circRNA dysregulation in several thyroid neoplasms and assess their potential for use as diagnostic and prognostic biomarkers.

Update on Molecular Diagnostics in Thyroid Pathology: A Review

Thyroid nodules are quite common, and the determination of a nodule of concern is complex, involving serum testing, radiology and, in some cases, pathological evaluation. For those nodules that raise clinical concern of neoplasia, fine needle aspiration biopsy is the gold standard for evaluation; however, in up to 30% of cases, results are indeterminate for malignancy, and further testing is needed. Advances in molecular testing have shown it to be of benefit for both diagnostic and prognostic purposes, and its use has become an integral part of thyroid cancer management in the United States and in several global nations. After The Cancer Genome Atlas (TCGA) consortium published its molecular landscape of papillary thyroid carcinoma (PTC) and reduced the "black matter" in PTC from 25% to 3.5%, further work ensued to clarify the remaining fraction not neatly attributed to the BRAF^V600E-like or RAS-like phenotypes of the TCGA. Over the past decade, commercial molecular platforms have been refined as data accrues, and they increasingly cover most genetic variants of thyroid carcinomas. Molecular reporting focuses on the nodule tested, including related clinical information for that nodule (size of nodule, Bethesda category, etc.). This results in a comprehensive report to physicians that may also include patient-directed, clear language that facilitates conversations about nodule management. In cases of advanced or recurrent disease, molecular testing may become essential for devising an individual therapeutic plan. In this review, we focus on the evolution of integrated molecular testing in thyroid nodules, and how our understanding of tumor genetics, combined with histopathology, is driving the next generation of rational patient management, particularly in the context of emerging small, targetable therapeutics.

New Opportunities for Preoperative Diagnosis of Medullary Thyroid Carcinoma

The preoperative diagnostics of medullary thyroid carcinoma (MTC), including the measuring of the blood calcitonin level, has a number of limitations. Particular focus has recently been placed on the role of miRNAs in the development of various malignant tumors; a comparative analysis of accuracy of the existing methods for MTC diagnosis with a novel diagnosis method, evaluation of the miRNA-375 expression level, was performed in this study. The expression level of miRNA-375 in cytology samples from 555 patients with the known histological diagnosis, including 41 patients with confirmed postoperative diagnosis of MTC, was assessed. The diagnostic parameters of the basal calcitonin level, calcitonin in wash-out fluid from the FNAB needle, and miRNA-375 were compared. An assessment of the miRNA-375 expression level made it possible to detect all the MTC samples with a 100% accuracy among all the 555 cytology specimens, as well as in non-informative FNAB specimens, and specimens from the ipsilateral thyroid lobe. Parameters such as sensitivity, specificity, PPV, and NPV were 100%. The miRNA-375 level, unlike calcitonin, does not correlate with tumor volume, so it does not have the so-called "gray zone". An assessment of the miRNA-375 expression allows one to accurately distinguish MTC from other malignant and benign thyroid tumors.

Molecular diagnostics in the evaluation of thyroid nodules: Current use and prospective opportunities

Thyroid cancer is the most common endocrine malignancy with an estimated 43,800 new cases to be diagnosed in 2022 and representing the 7th most common cancer in women. While thyroid nodules are very common, being identified in over 60% of randomly selected adults, only 5-15% of thyroid nodules harbor thyroid malignancy. Therefore, it is incumbent upon physicians to detect and treat thyroid malignancies as is clinically appropriate and avoid unnecessary invasive procedures in patients with benign asymptomatic lesions. Over the last 15-20 years, rapid advances have been made in cytomolecular testing to aid in thyroid nodule management. Initially, indeterminate thyroid nodules, those with Bethesda III or IV cytology and approximately a 10-40% risk of malignancy, were studied to assess benignity or malignancy. More recently, next generation sequencing and micro-RNA technology platforms have refined the diagnostic capacity of thyroid nodule molecular testing and have introduced opportunities to glean prognostic information from both cytologically indeterminate and malignant thyroid nodules. Therefore, clinicians can move beyond determination of malignancy, and utilize contemporary molecular information to aid in decisions such as extent of surgery and post-therapy monitoring plans. Future opportunities include molecularly derived information about tumor behavior, neo-adjuvant treatment opportunities and response to thyroid cancer therapies.

Follicular Neoplasm of Thyroid Revisited: Current Differential Diagnosis and the Impact of Molecular Testing

The diagnosis of "follicular neoplasm" (FN) in thyroid cytopathology has a long history that originated not long after the practice of fine-needle aspiration (FNA) of thyroid nodules. From the outset, this interpretive category was intended to convey a set of differential diagnoses rather than a precise diagnosis, as key diagnostic features, such as capsular and vascular invasion, were not detectable on cytology preparations. Cytologic-histologic correlation studies over the past several decades have shown that FN interpretation can be applied to the spectrum of nonneoplastic tumors to carcinomas. Most tumors classified as FN include follicular adenoma, follicular carcinoma, noninvasive follicular thyroid tumor with papillary-like nuclear features, and follicular variant of papillary thyroid carcinoma. Less common entities that may be classified as FN on FNA include hyalinizing trabecular tumor (HTT), poorly differentiated thyroid carcinoma, medullary carcinoma, and nonthyroidal lesions such as parathyroid tissue, paraganglioma, and metastatic tumors. Advances in our ability to detect characteristic molecular alterations (eg, GLIS gene rearrangements for hyalinizing trabecular tumor) in FNA samples may assist in the identification of some of these entities. In this review, we summarize the pathophysiology, history, and evolution of the terminology and the current differential diagnosis according to the recently published 2022 World Health Organization classification, molecular testing, and management of nodules classified as FN.

A Retrospective Evaluation of the Diagnostic Performance of an Interdependent Pairwise MicroRNA Expression Analysis with a Mutation Panel in Indeterminate Thyroid Nodules

Background: The addition of genetic analysis to the evaluation of thyroid nodule fine-needle aspiration biopsy samples improves diagnostic accuracy of cytologically indeterminate thyroid nodules (ITNs) with Bethesda III or IV cytopathology. We previously reported the performance of a multiplatform molecular test, referred to in this study as MPTXv1, that includes a mutation panel (ThyGeNEXT^®) plus an algorithmic microRNA (miRNA) risk classifier (ThyraMIR^®). Complex interactions of growth-promoting and -suppressing miRNAs affect the phenotype. We previously demonstrated that accounting for these interactions with pairwise miRNA expression analysis improves the diagnosis of medullary thyroid carcinoma. In this study, we assess the impact of pairwise miRNA expression analysis on risk stratification of ITNs. Methods: Pairwise expression analysis of 11 miRNAs was performed on a training cohort of histopathology-proven benign nodules (n = 50) to define the mean and standard deviation of each pairwise analysis and create a Benign/Malignant Profiler (MPTXv2), deviations from which predicted the malignancy risk. Clinical validation of MPTXv2 was assessed using a cohort of 178 ITN (Bethesda III and IV) samples from a multicentered, blinded retrospective study, previously evaluated by MPTXv1. Results: Compared with MPTXv1, MPTXv2 significantly improved the test performance. The receiver operating characteristic (ROC) areas under the curve (AUC) increased from 0.85 to 0.97 (p < 0.001), and the diagnostic accuracy at the positive threshold increased significantly (p < 0.05) from 83% [95% confidence interval (CI) = 76-88] to 93% [CI = 89-96]. The significant improvement in the ROC AUC and the diagnostic accuracy was due to a strong statistical trend for improvement in specificity at the positive threshold. At the positive threshold, the specificity for MPTXv1 was 90% [CI = 84-95] and improved to 98% [CI = 94-99] for MPTXv2. Using the MPTXv2, the Moderate-Risk cohort decreased from 50 samples (28% of the cohort) to 24 samples (13% of the cohort). This 52% decrease is statistically significant (p < 0.001) and clinically meaningful. Conclusion: As compared with MPTXv1, pairwise miRNA expression analysis used in MPTXv2 significantly improved the diagnostic accuracy of ITN risk stratification and reduced the size of the Moderate-Risk group. Prospective trials are indicated to confirm these findings in a clinical practice setting.

Update on the Diagnosis and Management of Medullary Thyroid Cancer: What Has Changed in Recent Years?

Medullary thyroid carcinoma (MTC) is a neoplasm originating from parafollicular C cells. MTC is a rare disease, but its prognosis is less favorable than that of well-differentiated thyroid cancers. To improve the prognosis of patients with MTC, early diagnosis and prompt therapeutic management are crucial. In the following paper, recent advances in laboratory and imaging diagnostics and also pharmacological and surgical therapies of MTC are discussed. Currently, a thriving direction of development for laboratory diagnostics is immunohistochemistry. The primary imaging modality in the diagnosis of MTC is the ultrasound, but opportunities for development are seen primarily in nuclear medicine techniques. Surgical management is the primary method of treating MTCs. There are numerous publications concerning the stratification of particular lymph node compartments for removal. With the introduction of more effective methods of intraoperative parathyroid identification, the complication rate of surgical treatment may be reduced. The currently used pharmacotherapy is characterized by high toxicity. Moreover, the main limitation of current pharmacotherapy is the development of drug resistance. Currently, there is ongoing research on the use of tyrosine kinase inhibitors (TKIs), highly specific RET inhibitors, radiotherapy and immunotherapy. These new therapies may improve the prognosis of patients with MTCs.

Circulating Plasma MicroRNA in Patients With Active Acromegaly

CONTEXT

Excessive production of growth hormone causes marked multiorgan changes in patients with acromegaly, which may involve epigenetic mechanisms.

OBJECTIVE

To evaluate differences in circulating microRNAs (miRNAs) associated with chronic growth hormone overproduction in adults.

DESIGN AND SETTING

A cross-sectional case-control study was conducted at a tertiary medical center.

PARTICIPANTS

We enrolled 12 consecutive patients with acromegaly along with 12 age- and sex-matched controls in the discovery phase of the study and then extended this cohort to 47 patients with acromegaly and 28 healthy controls for the validation study.

MAIN OUTCOME MEASURES

Plasma miRNAs were quantified by next-generation sequencing (NGS) in the discovery phase. Levels of selected miRNAs were validated on extended cohorts using reverse transcription quantitative polymerase chain reaction (RT-qPCR), compared between groups, and correlated with clinical parameters.

RESULTS

Based on NGS data, we selected 3 plasma miRNAs downregulated in patients with acromegaly compared to healthy controls: miR-4446-3p -1.317 (P = 0.001), miR-215-5p -3.040 (P = 0.005), and miR-342-5p -1.875 (P = 0.013) without multiplicity correction for all 3 miRNAs. These results were confirmed by RT-qPCR in the validation phase for 2 miRNAs out of 3: miR-4446-3p (P < 0.001, Padjusted < 0.001), area under the receiver-operator curve (AUC) 0.862 (95% CI 0.723-0.936; P < 0.001) and miR-215-5p (P < 0.001, Padjusted < 0.001), AUC 0.829 (95% CI 0.698-0.907; P < 0.001) to differentiate patients with acromegaly from healthy controls.

CONCLUSIONS

In a 2-phase experiment using 2 different techniques we found and validated the downregulation of plasma miR-4446-3p and miR-215-5p in patients with acromegaly compared to healthy subjects, which makes them promising biomarkers for further research.

RAS mutation and associated risk of malignancy in the thyroid gland: An FNA study with cytology-histology correlation

BACKGROUND

Activating point mutations of the RAS gene (NRAS, HRAS, and KRAS) can be seen in benign and malignant thyroid tumors; among these, NRAS mutations are more commonly seen. This study was conducted to evaluate the thyroid risk of malignancy (ROM) associated with RAS mutations in thyroid fine-needle aspiration (FNA) at the authors' institution.

METHODS

The authors searched their electronic database system between January 2015 and May 2021 for thyroid FNA cases with any type of RAS mutation. Molecular alterations were identified with the ThyroSeq Genomic Classifier, ThyGeNEXT (thyroid oncogene panel)/ThyraMIR (miRNA classifier), or ThyroSure gene panel.

RESULTS

A total of 127 cases (age, 51 ± 14 years; 100 females and 27 males) were identified, and 72 had histologic follow-up. The overall ROM associated with RAS mutations (with or without any other molecular alterations) was 29%, whereas the ROM was lower (18%) with RAS mutations only. Isolated NRAS, HRAS, and KRAS mutation-associated ROMs were 15%, 27%, and 14%, respectively. Among these RAS-mutated cases, the cases with a Bethesda category IV cytologic diagnosis had a higher ROM than the cases with a category III diagnosis (38% vs 17%). Twenty-one histologically confirmed malignant cases were mostly classified on cytology as category IV lesions (14 of 34; 41%), and the remainder were either category III (6 of 35; 17%) or V lesions (1 of 1; 100%).

CONCLUSIONS

This study demonstrated that the overall RAS mutation-associated ROM in thyroid FNA was intermediate (29%), and isolated HRAS mutations appeared to have a higher ROM (27%) than NRAS and KRAS mutations (15% and 14%, respectively).

Medullary thyroid carcinoma

PURPOSE OF REVIEW

To summarize recent developments in the diagnosis and management of patients with medullary thyroid cancer (MTC), with a focus on pathogenesis, systemic therapy, and future directions.

RECENT FINDINGS

The addition of mutational analysis to cytological assessment of thyroid nodules has improved the diagnostic accuracy of MTC. The discovery of new genomic alterations and overexpression of certain factors allows for improved prognostication in MTC and provides potentially new therapeutic agents. New data suggest that tumor environment may be more immunogenic than previously thought in a subset of MTCs with identification of a new MTC-specific antigen leading to a revival of investigating immune-based therapy for this disease. The newly approved selective rearranged during transfection (RET0-inhibitors, selpercatinib and pralsetinib, offer promising results, and tolerability for patients with RET-mutated MTC; however, the development of resistance mechanisms may be problematic.

SUMMARY

MTC has witnessed remarkable advancements in recent years. Our new understanding of some of the driver mutations in MTC allows for therapeutics with more tolerable adverse event profiles. However, there is still a need for more effective treatment strategies for subsets of patients without actionable mutations and for those who develop resistance to currently available therapies.

Molecular Tests for Risk-Stratifying Cytologically Indeterminate Thyroid Nodules: An Overview of Commercially Available Testing Platforms in the United States

The past decade has witnessed significant advances in the application of molecular diagnostics for the pre-operative risk-stratification of cytologically indeterminate thyroid nodules. The tests that are currently marketed in the United States for this purpose combine aspects of tumor genotyping with gene and/or microRNA expression profiling. This review compares the general methodology and clinical validation studies for the three tests currently offered in the United States: ThyroSeq v3, Afirma GSC and Xpression Atlas, and ThyGeNEXT/ThyraMIR.

Analytical and clinical validation of pairwise microRNA expression analysis to identify medullary thyroid cancer in thyroid fine-needle aspiration samples

Background

Medullary thyroid carcinoma (MTC) is an aggressive malignancy originating from the parafollicular C cells. Preoperatively, thyroid nodule fine‐needle aspiration cytology (FNAC) and pathogenic gene mutations are definitive in approximately one‐half of cases. MicroRNAs (miRNAs) are endogenous, noncoding, single‐stranded RNAs that regulate gene expression, a characteristic that confers the potential for identifying malignancy. In the current study, the authors hypothesized that differential pairwise (diff‐pair) analysis of miRNA expression levels would reliably identify MTC in FNA samples.

Methods

The relative abundance of 10 different miRNAs in total nucleic acids was obtained from ThyraMIR test results. Diff‐pair analysis was performed by subtracting the critical threshold value of one miRNA from the critical threshold values of other miRNAs. Next‐generation sequencing with the ThyGeNEXT panel identified oncogenic gene alterations. The discovery cohort consisted of 30 formalin‐fixed, paraffin‐embedded benign and malignant thyroid neoplasms, including 4 cases of MTC. After analytical validation, clinical validation was performed using 3 distinct cohorts (total of 7557 specimens).

Results

In the discovery cohort, 9 diff‐pairs were identified as having significant power using the Kruskal‐Wallis test (P < .0001) to distinguish MTC samples from non‐MTC samples. The assay correctly classified all MTC and non‐MTC samples in the analytical validation study and in the 3 clinical validation cohorts. The overall test accuracy was 100% (95% confidence interval, 99%‐100%). In indeterminate FNAC samples, the sensitivity of the diff‐pair analysis was greater than that of the MTC‐specific mutation analysis (100% vs 25%; P = .03).

Conclusions

Pairwise miRNA expression analysis of ThyraMIR results were found to accurately predict MTC in thyroid FNA samples, including those with indeterminate FNAC findings.

The authors have developed and validated a microRNA (miRNA) test for the detection of medullary thyroid cancer (MTC) in preoperative thyroid nodule samples. The method, based on differential pairwise analysis of miRNA expression data generated using the ThyraMIR Thyroid miRNA Classifier, accurately predicts MTC with 100% sensitivity and 100% specificity in thyroid fine‐needle aspiration biopsies.