RET/PTC rearrangement is prevalent in follicular Hürthle cell carcinomas

Uncommon molecular alterations in follicular-derived thyroid carcinoma: A single institution study

Thyroid carcinomas are the most common endocrine malignancy and commonly have alterations in the mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3 kinase (PI3K)/AKT signaling pathways in well-differentiated tumors. Alternative molecular alterations driving thyroid carcinomas have been identified rarely in the literature and are more likely to occur in poorly differentiated or anaplastic cases. In this study, uncommon genetic alterations such as MLH1, MSH2, NSD3::NUTM1, RET::SPECC1L, and G3BP2::FGFR2 were identified in patients with papillary thyroid carcinoma, poorly differentiated thyroid carcinoma, and differentiated high-grade thyroid carcinoma. Most of these tumors demonstrated an aggressive biological behavior. Atypical driver mutations in thyroid carcinomas can occur in patients with cancer predisposition syndromes as demonstrated by an NTRK1::TPM3 fusion in a patient with Li Fraumeni syndrome. In these settings of more aggressive disease, molecular testing targeting actionable fusions and mutations is important. As demonstrated in our case cohort, 100% of cases diagnosed as high-grade follicular-derived thyroid carcinoma had a mutation or fusion that is associated with worse prognosis, has a germline syndrome association requiring further work up, or an actionable mutation. This high yield seen in this cohort for molecular testing in patients with high-grade follicular-derived thyroid carcinoma suggests more routine molecular testing in this population would be a beneficial clinical practice.

Predictive molecular pathology in metastatic thyroid cancer: the role of RET fusions

BACKGROUND

Rearranged during transfection (RET) gene fusions are detected in 10-20% of thyroid cancer patients. Recently, RET fusion-positive metastatic thyroid cancers have attracted much attention owing to the FDA approval of two highly selective anti-RET tyrosine kinase inhibitors, namely, selpercatinib, and pralsetinib.

AREAS COVERED

This review summarizes the available evidence on the biological and predictive role of RET gene fusions in thyroid carcinoma patients and the latest screening assays currently used to detect these genomic alterations in histological and cytological specimens.

EXPERT OPINION

Management of advanced thyroid carcinoma has significantly evolved over the last decade thanks to the approval of three multikinase inhibitors, i.e. sorafenib, lenvatinib, cabozantinib, and of two selective RET-tyrosine inhibitors, i.e. selpercatinib and pralsetinib. In this setting, the detection of RET-fusions in advanced thyroid cancer specimens through the use of next-generation sequencing has become a commonly used strategy in clinical practice to select the best treatment options.

Pralsetinib for patients with advanced or metastatic RET-altered thyroid cancer (ARROW): a multi-cohort, open-label, registrational, phase 1/2 study

BACKGROUND

Oncogenic alterations in RET represent important therapeutic targets in thyroid cancer. We aimed to assess the safety and antitumour activity of pralsetinib, a highly potent, selective RET inhibitor, in patients with RET-altered thyroid cancers.

METHODS

ARROW, a phase 1/2, open-label study done in 13 countries across 71 sites in community and hospital settings, enrolled patients 18 years or older with RET-altered locally advanced or metastatic solid tumours, including RET-mutant medullary thyroid and RET fusion-positive thyroid cancers, and an Eastern Co-operative Oncology Group performance status of 0-2 (later limited to 0-1 in a protocol amendment). Phase 2 primary endpoints assessed for patients who received 400 mg once-daily oral pralsetinib until disease progression, intolerance, withdrawal of consent, or investigator decision, were overall response rate (Response Evaluation Criteria in Solid Tumours version 1.1; masked independent central review) and safety. Tumour response was assessed for patients with RET-mutant medullary thyroid cancer who had received previous cabozantinib or vandetanib, or both, or were ineligible for standard therapy and patients with previously treated RET fusion-positive thyroid cancer; safety was assessed for all patients with RET-altered thyroid cancer. This ongoing study is registered with clinicaltrials.gov, NCT03037385, and enrolment of patients with RET fusion-positive thyroid cancer was ongoing at the time of this interim analysis.

FINDINGS

Between Mar 17, 2017, and May 22, 2020, 122 patients with RET-mutant medullary and 20 with RET fusion-positive thyroid cancers were enrolled. Among patients with baseline measurable disease who received pralsetinib by July 11, 2019 (enrolment cutoff for efficacy analysis), overall response rates were 15 (71%) of 21 (95% CI 48-89) in patients with treatment-naive RET-mutant medullary thyroid cancer and 33 (60%) of 55 (95% CI 46-73) in patients who had previously received cabozantinib or vandetanib, or both, and eight (89%) of nine (95% CI 52-100) in patients with RET fusion-positive thyroid cancer (all responses confirmed for each group). Common (≥10%) grade 3 and above treatment-related adverse events among patients with RET-altered thyroid cancer enrolled by May 22, 2020, were hypertension (24 patients [17%] of 142), neutropenia (19 [13%]), lymphopenia (17 [12%]), and anaemia (14 [10%]). Serious treatment-related adverse events were reported in 21 patients (15%), the most frequent (≥2%) of which was pneumonitis (five patients [4%]). Five patients [4%] discontinued owing to treatment-related events. One (1%) patient died owing to a treatment-related adverse event.

INTERPRETATION

Pralsetinib is a new, well-tolerated, potent once-daily oral treatment option for patients with RET-altered thyroid cancer.

FUNDING

Blueprint Medicines.

Diagnostic and prognostic value of a 7-panel mutation testing in thyroid nodules with indeterminate cytology: the SWEETMAC study

PURPOSE

The aim of this prospective study (ClinicalTrials.gov: NCT01880203) was to evaluate the diagnostic and prognostic value of a 7-panel mutation testing in the aspirates of thyroid nodules with indeterminate cytology (IC).

METHODS

Eligible patients had a thyroid nodule ≥15 mm with IC (Bethesda III-V) for which surgery had been recommended. Detection of BRAF and RAS mutations was performed using pyrosequencing and RET/PTC and PAX8/PPARγ rearrangements using Real-Time quantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Among 131 nodules with IC, 21 (16%) were malignant including 20 differentiated cancers and one thyroid lymphoma. Molecular abnormalities were identified in 15 nodules with IC corresponding to 10 malignant and 5 benign tumours. BRAF mutation was detected in 4 nodules all corresponding to classic PTC, and PAX8/PPARγ rearrangement in 2 HCC. In contrast, RAS mutation was identified in eight nodules, of which four were malignant, and one RET/PTC3 rearrangement in a follicular adenoma. This data resulted in an accuracy of 88%, sensitivity of 48%, specificity of 95%, positive-predictive value of 67%, and negative-predictive value of 91%. After a 56 month's follow-up, the proportion of excellent response was similar in patients with molecular alterations (67%) and those without (60%).

CONCLUSIONS

By increasing the overall risk of cancer from 16 to 67% in mutated nodules and by diminishing it to 9% in wild-type, this study confirms the relevance of the 7-panel mutation testing in the diagnostic of nodules with IC. Genetic testing, however, did not predict outcome in the cancer patient subgroup.

Challenges in Cytology Specimens With Hürthle Cells

In fine-needle aspirations (FNA) of thyroid, Hürthle cells can be found in a broad spectrum of lesions, ranging from non-neoplastic conditions to aggressive malignant tumors. Recognize them morphologically, frequently represents a challenging for an adequately diagnosis and are associated with a significant interobserver variability. Although the limitations of the morphologic diagnosis still exist, the interpretation of the context where the cells appear and the recent advances in the molecular knowledge of Hürthle cells tumors are contributing for a more precise diagnosis. This review aims to describe the cytology aspects of all Hürthle cells neoplastic and non-neoplastic thyroid lesions, focusing on the differential diagnosis and reporting according to The Bethesda System for Reporting Thyroid Cytology (TBSRTC). New entities according to the latest World Health Organization (WHO) classification are included, as well as an update of the current molecular data.

Genetics, Diagnosis, and Management of Hürthle Cell Thyroid Neoplasms

Hürthle cell lesions have been a diagnostic conundrum in pathology since they were first recognized over a century ago. Controversy as to the name of the cell, the origin of the cell, and even which cells in particular may be designated as such still challenge pathologists and confound those treating patients with a diagnosis of "Hürthle cell" anything within the diagnosis, especially if that anything is a sizable mass lesion. The diagnosis of Hürthle cell adenoma (HCA) or Hürthle cell carcinoma (HCC) has typically relied on a judgement call by pathologists as to the presence or absence of capsular and/or vascular invasion of the adjacent thyroid parenchyma, easy to note in widely invasive disease and a somewhat subjective diagnosis for minimally invasive or borderline invasive disease. Diagnostic specificity, which has incorporated a sharp increase in molecular genetic studies of thyroid tumor subtypes and the integration of molecular testing into preoperative management protocols, continues to be challenged by Hürthle cell neoplasia. Here, we provide the improving yet still murky state of what is known about Hürthle cell tumor genetics, clinical management, and based upon what we are learning about the genetics of other thyroid tumors, how to manage expectations, by pathologists, clinicians, and patients, for more actionable, precise classifications of Hürthle cell tumors of the thyroid.

Comprehensive Assessment of TERT mRNA Expression across a Large Cohort of Benign and Malignant Thyroid Tumours

The presence of TERT promoter (TERTp) mutations in thyroid cancer have been associated with worse prognosis features, whereas the extent and meaning of the expression and activation of TERT in thyroid tumours is still largely unknown. We analysed frozen samples from a series of benign and malignant thyroid tumours, displaying non-aggressive features and low mutational burden in order to evaluate the presence of TERTp mutations and TERT mRNA expression in these settings. In this series, TERTp mutations were found in 2%, only in malignant cases, in larger cancers, and from older patients. TERT mRNA expression was detected in both benign and malignant tumours, with increased frequencies in the malignant tumours with aggressive histotypes, larger tumours, and from older patients. In benign tumours, TERT mRNA expression was found in 17% of the follicular thyroid adenoma (FTA) with increased levels of expression in smaller tumours and associated with the presence of thyroiditis. TERTp mutations and TERT mRNA expression are correlated with worse prognosis features in malignant thyroid tumours, whereas TERT mRNA expression in the benign tumours is associated with the presence of thyroiditis.

Hürthle-cell neoplasms of the thyroid: An algorithmic approach to pathologic diagnosis in light of molecular advances

Our understanding of neoplasia is evolving at a rapid pace in these exciting times, where recent molecular pathology advances are reinforcing and fine tuning morphological divisions and classification. Thyroid gland neoplasia in general, and Hürthle-cell neoplasms in particular, are no exception in the current era of histopathology-molecular biology paradigm. In this review paper, we discuss the rationale that led pathologists in the past to separate Hürthle-cell neoplasms into its own dedicated diagnostic category, and provide an algorithmic approach to the differential diagnosis of oncocytic lesions of the thyroid. This review will also shed light on the current WHO classification of Hürthle-cell neoplasms in light of molecular advances that justify histopathologic distinctions.

Prognostic significance of TERT promoter and BRAF mutations in TIR-4 and TIR-5 thyroid cytology

OBJECTIVE

Follicular-derived thyroid cancers generally have a good prognosis, but in a minority of cases, they have an aggressive behavior and develop distant metastases, with an increase in the associated mortality. None of the prognostic markers currently available prior to surgery can identify such cases.

METHODS

TERT promoter and BRAF gene mutations were examined in a series of 436 consecutive TIR-4 and TIR-5 nodes referred for surgery. Follow-up (median: 59 months, range: 7-293 months) was available for 384/423 patients with malignant nodes.

RESULTS

TERT promoter and BRAF mutations were detected in 20/436 (4.6%) and 257/434 thyroid nodules (59.2%), respectively. At the end of the follow-up, 318/384 patients (82.8%) had an excellent outcome, 48/384 (12.5%) had indeterminate response or biochemical persistence, 18/384 (4.7%) had a structural persistence or died from thyroid cancer. TERT promoter mutations correlated with older age (P < 0.0001), larger tumor size (P = 0.0002), oxyntic and aggressive PTC variants (P = 0.01), higher tumor stages (P < 0.0001), distant metastases (<0.0001) and disease outcome (P < 0.0001). At multivariate analysis, TERT promoter mutation was not an independent predictor of disease outcome. TERT promoter mutation- (OR: 40.58; 95% CI: 3.06-539.04), and N1b lymph node metastases (OR: 40.16, 95% CI: 3.48-463.04) were independent predictors of distant metastases. BRAF mutation did not predict the outcome, and it correlated with a lower incidence of distant metastases (P = 0.0201).

CONCLUSIONS

TERT promoter mutation proved an independent predictor of distant metastases, giving clinicians the chance to identify many of the patients who warranted more aggressive initial treatment and closer follow-up.

mTOR Pathway in Papillary Thyroid Carcinoma: Different Contributions of mTORC1 and mTORC2 Complexes for Tumor Behavior and SLC5A5 mRNA Expression

The mammalian target of rapamycin (mTOR) pathway is overactivated in thyroid cancer (TC). We previously demonstrated that phospho-mTOR expression is associated with tumor aggressiveness, therapy resistance, and lower mRNA expression of SLC5A5 in papillary thyroid carcinoma (PTC), while phospho-S6 (mTORC1 effector) expression was associated with less aggressive clinicopathological features. The distinct behavior of the two markers led us to hypothesize that mTOR activation may be contributing to a preferential activation of the mTORC2 complex. To approach this question, we performed immunohistochemistry for phospho-AKT Ser473 (mTORC2 effector) in a series of 182 PTCs previously characterized for phospho-mTOR and phospho-S6 expression. We evaluated the impact of each mTOR complex on SLC5A5 mRNA expression by treating cell lines with RAD001 (mTORC1 blocker) and Torin2 (mTORC1 and mTORC2 blocker). Phospho-AKT Ser473 expression was positively correlated with phospho-mTOR expression. Nuclear expression of phospho-AKT Ser473 was significantly associated with the presence of distant metastases. Treatment of cell lines with RAD001 did not increase SLC5A5 mRNA levels, whereas Torin2 caused a ~6 fold increase in SLC5A5 mRNA expression in the TPC1 cell line. In PTC, phospho-mTOR activation may lead to the activation of the mTORC2 complex. Its downstream effector, phospho-AKT Ser473, may be implicated in distant metastization, therapy resistance, and downregulation of SLC5A5 mRNA expression.

Metabolic Reprogramming in Thyroid Carcinoma

Among all the adaptations of cancer cells, their ability to change metabolism from the oxidative to the glycolytic phenotype is a hallmark called the Warburg effect. Studies on tumor metabolism show that improved glycolysis and glutaminolysis are necessary to maintain rapid cell proliferation, tumor progression, and resistance to cell death. Thyroid neoplasms are common endocrine tumors that are more prevalent in women and elderly individuals. The incidence of thyroid cancer has increased in the Past decades, and recent findings describing the metabolic profiles of thyroid tumors have emerged. Currently, several drugs are in development or clinical trials that target the altered metabolic pathways of tumors are undergoing. We present a review of the metabolic reprogramming in cancerous thyroid tissues with a focus on the factors that promote enhanced glycolysis and the possible identification of promising metabolic targets in thyroid cancer.

ROS-induced near-homozygous genomes in thyroid cancer

A near-homozygous genome (NHG) is especially seen in a subset of follicular thyroid cancer of the oncocytic type (FTC-OV). An NHG was also observed in the metabolically relatively quiescent cell lines XTC.UC1, a model for FTC-OV, and in FTC-133, -236 and -238, the latter three derived from one single patient with follicular thyroid cancer. FTC-236 subclones showed subtle whole-chromosome differences indicative of sustained reciprocal mitotic missegregations. Reactive oxygen species (ROS) scavenger experiments reduced the number of chromosomal missegregations in XTC.UC1 and FTC-236, while pCHK2 was downregulated in these cells. Treatment with antimycin A increased ROS indicated by enhanced MitoSOX Red and pCHK2 fluorescence in metaphase cells. In a selected set of oncocytic follicular thyroid tumors, increasing numbers of whole-chromosome losses were observed toward an aggressive phenotype, but with retention of chromosome 7. Together, ROS activates CHK2 and links to the stepwise loss of whole chromosomes during tumor progression in these lesions. We postulate that sequential loss of whole chromosomes is a dominant driver of the oncogenesis of a subset of follicular thyroid tumors.

Fluorescence in situ hybridization of thyroid fine-needle aspiration biopsy distinguishes between neoplastic and non-neoplastic Hürthle cell lesions

INTRODUCTION

Fine-needle aspiration (FNA) biopsy of Hürthle cell proliferations can be difficult to characterize based purely on morphologic features. Studies have shown Hürthle cell neoplasms often demonstrate gains in chromosomes 5, 7, and 12. This study examined fluorescence in situ hybridization (FISH) performance characteristics in non-neoplastic and neoplastic Hürthle cell proliferations sampled by FNA biopsy in order to assess chromosome patterns.

MATERIALS AND METHODS

FNA biopsies of Hürthle cell proliferations, including nodular hyperplasia (NH), Hürthle cell adenoma (HCA), and Hürthle cell carcinoma (HCC), that had subsequent surgical excision were selected. FISH was performed on an air-dried, modified Wright-Giemsa-stained, aspirate smear slide from each case using a 3-color panel consisting of 1 subtelomeric and 2 centromeric probes for chromosomes 5, 7, and 12. Chromosomal probe patterns were recorded in up to 50 cells. A positive result was considered when >15% of cells showed a polysomy in 2 or more chromosomes.

RESULTS

A total of 25 cases were included in the study. All cases of NH were negative, and 7 of 9 (78%) HCAs and 8 of 12 (67%) HCCs were positive. Of the positive cases, 2 of the 7 (29%) HCAs showed >50% of cells with polysomy, and 5 of the 8 (63%) HCCs showed >50% of the cells with polysomy.

CONCLUSION

Thyroid FNA biopsy can identify Hürthle cell proliferations; risk stratification based on morphology is difficult, however. FISH chromosomal evaluation of thyroid FNA biopsies is useful to distinguish neoplastic from non-neoplastic Hürthle cell proliferation.

Etiopathogenesis of oncocytomas

Oncocytomas are distinct tumors characterized by an abnormal accumulation of defective and (most probably) dysfunctional mitochondria in cell cytoplasm of such tumors. This particular phenotype has been studied for the last decades and the clarification of the etiopathogenic causes are still needed. Several mechanisms involved in the formation and maintenance of oncocytomas are accepted as reasonable causes, but the relevance and contribution of each one for oncocytic transformation may depend on different cancer etiopathogenic contexts. In this review, we describe the current knowledge of the etiopathogenic events that may lead to oncocytic transformation and discuss their contribution for tumor progression and mitochondrial accumulation.

EWSR1 rearrangement is a frequent event in papillary thyroid carcinoma and in carcinoma of the thyroid with Ewing family tumor elements (CEFTE)

Carcinomas of the thyroid with Ewing family tumor element (CEFTEs) are small-cell thyroid tumors with epithelial differentiation that disclose p63 expression and EWSR1-FLI1 rearrangement, carry a favorable prognosis and may co-exist with papillary thyroid carcinoma (PTC) foci. Two histogenetic hypotheses have been advanced regarding the origin of CEFTEs: arising in PTCs or in solid cell nests (SCN). A total of 3 CEFTEs, 54 PTCs, and 10 SCNs were reviewed, and fluorescence in situ hybridization (FISH) technique was performed in all cases to search for the presence of EWSR1 rearrangements. The three CEFTEs disclosed the EWSR1-FLI1 rearrangement both in the small cell and in the PTC component. Out of the 54 PTC cases, 28 (51.9%) were positive, 20 (37.0%) were negative, and 6 (11.1%) were inconclusive for EWSR1 rearrangement; in two of the positive PTC cases, the EWSR1-FLI1 rearrangement was detected. Classic PTC disclosed more often the EWSR1 rearrangement than other PTC variants (p = 0.031). PTCs with EWSR1 rearrangement disclosed a lower percentage of nuclei with EWSR1 polysomy than those without EWSR1 rearrangement (p = 0.001). Out of the 10 SCNs, 7 (70.0%) were negative and 3 (30.0%) were inconclusive for the EWSR1 rearrangement. Monosomic nuclei were more frequent (mean of 44.3%) in SCNs than in PTCs (p < 0.001). The presence of the EWSR1-FLI1 rearrangement in PTC component of all studied CEFTEs and the existence of the EWSR1 rearrangement in some PTCs favor the origin of CEFTE from PTC. The high frequency of EWSR1 rearrangements in PTC may represent a new diagnostic marker of these tumors.

RAS Mutations, and RET/PTC and PAX8/PPAR-gamma Chromosomal Rearrangements Are Also Prevalent in Benign Thyroid Lesions: Implications Thereof and A Systematic Review

BACKGROUND

Molecular markers associated with thyroid malignancy are increasingly being used as differential diagnostic tools for thyroid nodules. However, little has been reported recently regarding the prevalence of these markers in benign lesions. The literature was systematically reviewed to examine studies that reported on the prevalence of these markers in benign thyroid lesions.

METHODS

Appropriate studies published between January 1, 2000, and April 30, 2015, and cataloged in PubMed, Embase, Cochrane, Scopus, and Web of Science databases were searched for by combining different keywords for "thyroid tumor" with both general and specific keywords for "molecular marker" by using "AND" as the Boolean operator. All studies meeting criteria that reported the prevalence of RAS mutations, and RET/PTC and PAX8/PPAR-gamma chromosomal rearrangements in benign thyroid lesions were included for study.

RESULTS

A total of 64 articles (including 8162 patients, of whom 42.5% had benign lesions) that met all the study criteria were systematically reviewed and abstracted. Among 35 studies examining RAS mutations, the reported prevalence of RAS mutation in benign lesions ranged from 0% to 48%. In 38 studies examining RET/PTC rearrangements, the prevalence in benign lesions ranged from 0% to 68%. PAX8/PPAR-gamma rearrangements were examined in 27 studies, with the prevalence in benign lesions ranging from 0% to 55%.

CONCLUSION

The presence of these biomarkers and the tremendous variation in reports of their prevalence in benign lesions suggests the need for caution when including these markers in diagnostic decisions. Further understanding of the importance of these markers, as well as newly discovered markers of thyroid malignancy, may be required in order to avoid overtreatment of patients with benign thyroid tumors.

Hürthle Cells Adenoma of the Thyroid with Post-surgical Implants in the Neck: Clinical, Morphological, and Molecular Analysis of Three Cases

Thyroid implants in the soft tissue of the neck are very rare findings of traumatic, iatrogenic, or neoplastic origins. We describe the clinico-pathological and molecular analysis of three cases with an initial diagnosis of follicular adenoma, Hürthle cell variant (FA-HCT), which developed cervical thyroid implants at 60, 59, and 36 months after thyroid surgery, followed by further neck recurrences, and, eventually, by distant metastases. A systematic review of all histopathological samples of both the primary lesions and the neck implants was performed. Molecular study included the analysis of pan-RAS and BRAF mutations and RET/PTC1, RET/PTC3, and PAX8/PPARγ rearrangements. The review of the original slides and of additional re-cuts of each block of the thyroid lesions did not show any sign of capsular and/or vascular invasion; thus, the original diagnoses of FA-HCT were confirmed. When sampling adequacy was considered, it turned out that the capsule was completely evaluable in case #3, whereas 85 % was evaluable for case #1 and less than 50 % for case #2. We cannot exclude that cases #1 and #2 were carcinomas that had not been completely sampled. The first occurring neck implants showed neither histological signs of malignancy nor the presence of lymphoid tissue. However, further neck recurrences had different histological aspects, with a clear infiltrative growth. Moreover, a mesenchymal reaction forming a sort of capsule was observed around oncocytic cells along with signs of vascular invasion. Molecular analysis revealed no alterations in the genes and rearrangements studied. Oncocytic thyroid implants in the neck soft tissue should be regarded as metastasis, even in the absence of clear-cut signs of malignancy and in the case of a bona fide diagnosis of Hürthle cells adenoma of the thyroid.

pmTOR is a marker of aggressiveness in papillary thyroid carcinomas

BACKGROUND

Activation of the mTOR pathway has been observed in thyroid cancer, but the biologic consequences regarding tumor behavior and patient prognosis remain poorly explored.

METHODS

We aimed to evaluate the associations of the mTOR pathway with clinicopathologic and molecular features and prognosis through the immunocharacterization of pmTOR and pS6 expression (as readouts of the pathway) in a series of 191 papillary thyroid carcinomas.

RESULTS

pmTOR expression was associated with distant metastases (P = .05) and persistence of disease (P = .05). Cases with greater expression of pmTOR were submitted to more ¹³¹I treatments (r[102] = 0.2; P = .02) and a greater cumulative dose of radioactive iodine (r[100] = 0.3; P = .01). Positive pmTOR expression showed to be an independent risk factor for distant metastases (odds ratio = 18.2; 95% confidence interval 2.1-157.9; P = .01). In contrast, pS6 expression was associated with absence of extrathyroid extension (P = .001), well-defined tumor margins (P = .05), and wild-type BRAF status (P = .01). There was no correlation between the expression of pmTOR and pS6 expression (r[140] = 0.1; P = .3).

CONCLUSION

pmTOR expression is an indicator of aggressive, metastatic papillary thyroid carcinoma, being possibly implicated in refractoriness to therapy, while pS6 expression is associated with less aggressive pathologic features. Further studies are needed to understand better the biologic consequences of activation of the mTOR pathway in the behavior of thyroid cancer, namely the contribution of other pmTOR downstream effectors.

Activating BRAF Mutations Detected in Mixed Hürthle Cell Carcinoma and Multifocal Papillary Carcinoma of the Thyroid Gland

Despite the increase in the incidence of thyroid carcinomas, the occurrence of collision tumors in the thyroid remains a rare event. We present the case of a 69-year-old female who presented to the emergency department with a chief complaint of painful neck swelling. Imaging revealed a large right hemithyroid mass and a left hemithyroid nodule. Fine needle aspiration of the lesions and subsequent total thyroidectomy revealed a Hürthle cell carcinoma in the right lobe and bilateral multicentric papillary carcinoma foci, including 2 foci with a classical pattern and 1 encapsulated follicular variant in the isthmus. BRAF gene mutation analysis revealed V600E gene mutation in the classical variants of papillary carcinoma and in the Hürthle cell carcinoma. The focus of follicular variant of papillary carcinoma in the isthmus and a sample from normal thyroid tissue did not harbor BRAF mutations. This case is remarkable in being an unusual report of a follicular Hürthle cell carcinoma harboring the BRAF V600E mutation and occurring in collision with multifocal papillary carcinoma. Documentation of such cases is important as it helps better understand the pathogenesis, clinical behavior, and radiologic findings of such rare lesions and to determine the optimal treatment modalities.

ENDOCRINE TUMOURS: Genetic predictors of thyroid cancer outcome

Genetic predictors of outcome are reviewed in the context of a disease--cancer--that can be (too) simplistically described as a 'successful, invasive clone of our own tissues'. Context has many faces that determine a thyroid cancer patient's outcome beyond the influence of genetic markers. There is also plenty of evidence on the prognostic meaning of the interplay between genetics and context/microenvironment factors (encapsulation, degree of invasion, staging, etc.). This review addresses only genetic alterations detected by molecular methods in surgically resected specimens, thus ruling out immunohistochemistry and (F)ISH, despite their crucial relevance as topographically oriented methods. For the sake of the discussion, well-differentiated carcinomas were divided into two main morphologic types: papillary carcinoma (classic and most variants) displaying BRAFV600E mutations and RET/papillary thyroid carcinoma rearrangements and the group of follicular patterned carcinomas that encompasses follicular carcinoma and the encapsulated form of follicular variant of papillary carcinoma, displaying RAS mutations and PAX8/PPARγ rearrangement. TERT promoter mutations have been recently described (and associated with distant metastases and reduced survival) in papillary and follicular carcinomas, as well as in poorly differentiated and undifferentiated carcinoma. TP53 mutations, previously thought to be restricted to less differentiated carcinomas, were also detected in papillary and follicular carcinoma and found to carry a guarded prognosis. Besides their putative importance for targeted therapies, the prognostic meaning of such mutations is discussed per se and in the setting of concurrent BRAF mutation.

DIAGNOSIS OF ENDOCRINE DISEASE: High-yield thyroid fine-needle aspiration cytology: an update focused on ancillary techniques improving its accuracy

Thyroid fine-needle aspiration (FNA) cytology is a fast growing field. One of the most developing areas is represented by molecular tests applied to cytological material. Patients that could benefit the most from these tests are those that have been diagnosed as 'indeterminate' on FNA. They could be better stratified in terms of malignancy risk and thus oriented with more confidence to the appropriate management. Taking in to consideration the need to improve and keep high the yield of thyroid FNA, professionals from various fields (i.e. molecular biologists, endocrinologists, nuclear medicine physicians and radiologists) are refining and fine-tuning their diagnostic instruments. In particular, all these developments aim at increasing the negative predictive value of FNA to improve the selection of patients for diagnostic surgery. These advances involve terminology, the application of next-generation sequencing to thyroid FNA, the use of immunocyto- and histo-chemistry, the development of new sampling techniques and the increasing use of nuclear medicine as well as molecular imaging in the management of patients with a thyroid nodule. Herein, we review the recent advances in thyroid FNA cytology that could be of interest to the 'thyroid-care' community, with particular focus on the indeterminate diagnostic category.

Afirma GEC and thyroid lesions: An institutional experience

BACKGROUND

Thyroid fine-needle aspiration (FNA) is used to assess appropriate management of nodular thyroid lesions safely, but Bethesda category III (atypia of undetermined significance/follicular lesion of undetermined significance) and category IV (follicular neoplasm/suspicious for follicular neoplasm) lesions are problematic. This study aimed to evaluate the Afirma Gene Expression Classifier (GEC) results for lesions in those categories.

METHODS

Medical records of patients with thyroid FNA and GEC results were obtained from archived material. Results were compared to thyroidectomy histologic diagnoses.

RESULTS

Among 66 patients with FNA results (47 women and 19 men aged 26-89 years [mean, 59.4 years]), surgical reports were available for 38. Afirma GEC results were "nondiagnostic" for 10 of 66 (15.2%), "benign" for 22 (33.3%), and "suspicious" for 34 (51.5%). Surgical diagnosis was available for 38 of 66 patients (57.6%); GEC results for 6 (15.8%) of these were "nondiagnostic," 27 (71.0%) were "suspicious," and 5 (13.2%) were "benign." One of 6 (16.7%) samples with "nondiagnostic" results, 1 of 5 (20%) with "benign" results, and 15 of 27 (55.6%) with "suspicious" results were malignant on histology. Papillary carcinoma was the most common tumor type (15 of 38; 39.5%).

CONCLUSIONS

Afirma GEC results minimize the number of unnecessary operations. Afirma GEC testing may be reserved for FNAs with a category III diagnosis on follow-up cytologic examination. We recommend a conservative approach for "suspicious" Afirma GEC results if Hürthle cells are seen with FNA.

Performance of the Afirma Gene Expression Classifier in Hürthle Cell Thyroid Nodules Differs from Other Indeterminate Thyroid Nodules

BACKGROUND

The recently introduced Afirma gene expression classifier (AGEC) provides binary results (benign or suspicious) to guide management of cytologically indeterminate thyroid nodules. The AGEC is intended to reduce unnecessary surgeries for benign nodules, and management algorithms favor surgery for suspicious results. Limited data are available on the performance of this test for Hürthle cell nodules (HCNs). This study hypothesized that a predominance of Hürthle cells leads to an increased rate of suspicious AGEC results with a potential for overtreatment, despite a relatively low risk of malignancy.

METHODS

The pathology databases from three tertiary care facilities were queried from 2010 to 2014 for fine-needle aspirates (FNAs) diagnosed as suspicious for Hürthle cell neoplasm (SHCN) or atypia of undetermined significance/follicular lesion of undetermined significance concerning for Hürthle cell neoplasm (AFHCN). Cytology diagnoses were rendered internally prior to AGEC testing. The patient demographics, FNA diagnosis, AGEC result, surgical procedure, and pathologic outcomes were recorded.

RESULTS

The cohort consisted of 134 patients with HCNs. Prior to AGEC availability, 62 patients underwent surgery: 81% (50/62) of patients had surgery, and 34% (17/50) of the resected index nodules were malignant. After introduction of the AGEC, 72 patients underwent AGEC testing: 65% (47/72) of patients had surgery, and 13% (6/46) of the resected nodules were malignant. Thirty-two percent (23/72) of patients had a benign AGEC result and did not undergo surgery, and 4% (3/72) had surgery despite a benign AGEC result with benign final pathology, whereas 63% (45/72) of patients had suspicious AGEC results, with 96% of these patients (43/45) undergoing surgery, and 14% (6/43) of these index nodules were malignant.

CONCLUSIONS

While 32% of tested patients declined surgery based on a benign AGEC, 86% of patients with suspicious AGEC findings had unnecessary surgery, reflecting a substantially lower rate of malignancy from what was previously reported for all indeterminate nodules. Given the approximate pretest malignancy risk of 25-35% for an FNA diagnosis of SHCN or AFHCN, a suspicious AGEC diagnosis does not increase the probability of malignancy in an HCN, and patients should be counseled accordingly.

Break-apart interphase fluorescence in situ hybridization assay in papillary thyroid carcinoma: on the road to optimizing the cut-off level for RET/PTC rearrangements

OBJECTIVE

Chromosomal rearrangements of the RET proto-oncogene is one of the most common molecular events in papillary thyroid carcinoma (PTC). However, their pathogenic role and clinical significance are still debated. This study aimed to investigate the prevalence of RET/PTC rearrangement in a cohort of BRAF WT PTCs by fluorescence in situ hybridization (FISH) and to search a reliable cut-off level in order to distinguish clonal or non-clonal RET changes.

DESIGN

Forty BRAF WT PTCs were analyzed by FISH for RET rearrangements. As controls, six BRAFV600E mutated PTCs, 13 follicular adenomas (FA), and ten normal thyroid parenchyma were also analyzed.

METHODS

We performed FISH analysis on formalin-fixed, paraffin-embedded tissue using a commercially available RET break-apart probe. A cut-off level equivalent to 10.2% of aberrant cells was accepted as significant. To validate FISH results, we analyzed the study cohort by qRT-PCR.

RESULTS

Split RET signals above the cut-off level were observed in 25% (10/40) of PTCs, harboring a percentage of positive cells ranging from 12 to 50%, and in one spontaneous FA (1/13, 7.7%). Overall, the data obtained by FISH matched well with qRT-PCR results. Challenging findings were observed in five cases showing a frequency of rearrangement very close to the cut-off.

CONCLUSIONS

FISH approach represents a powerful tool to estimate the ratio between broken and non-broken RET tumor cells. Establishing a precise FISH cut-off may be useful in the interpretation of the presence of RET rearrangement, primarily when this strategy is used for cytological evaluation or for targeted therapy.

Mitochondrial dynamics protein Drp1 is overexpressed in oncocytic thyroid tumors and regulates cancer cell migration

Oncocytic cell tumors are characterized by the accumulation of morphologically abnormal mitochondria in their cells, suggesting a role for abnormal mitochondrial biogenesis in oncocytic cell transformation. Little is known about the reason for the dysmorphology of accumulated mitochondria. The proteins regulating the morphology of mitochondria, the "mitochondria-shaping" proteins, can modulate their size and number; however, nothing is known hitherto about a possible involvement of mitochondrial dynamics in oncocytic cell transformation in tumors. Our aim was to assess the status of the mitochondria morphology and its role in oncocytic cell transformation. We therefore evaluated the expression pattern of the main mitochondrial fusion and fission proteins in a series of thyroid cell tumor samples, as well as in thyroid tumor cell lines, with and without oncocytic cell features. The expression of mitochondrial fusion (Opa1, Mfn1 and Mfn2) and fission (Drp1 and Fis1) proteins were evaluated by immunohistochemistry (IHC) in a series of 88 human thyroid tumors. In vitro studies, for comparative purposes and to deepen the study, were performed using TPC1 - a papillary thyroid carcinoma derived cell line—and XTC.UC1, an oncocytic follicular thyroid carcinoma-derived cell line. Both IHC and in vitro protein analyses showed an overall increase in the levels of "mitochondrial-shaping" proteins in oncocytic thyroid tumors. Furthermore, overexpression of the pro-fission protein Drp1 was found to be associated with malignant oncocytic thyroid tumors. Interestingly, genetic and pharmacological blockage of Drp1 activity was able to influence thyroid cancer cells’ migration/invasion ability, a feature of tumor malignancy. In this study we show that unbalanced mitochondrial dynamics characterize the malignant features of thyroid oncocytic cell tumors, and participate in the acquisition of the migrating phenotype.

Imaging, genetic testing, and biomarker assessment of follicular cell-derived thyroid cancer

Thyroid carcinoma is the most common endocrine malignancy worldwide, and its incidence continues to increase. As such the approach to a recently identified thyroid nodule is important to understand. The relevant imaging, examination, and need for fine-needle aspiration biopsy (FNA) are discussed. In approximately 25% of nodules, the diagnosis cannot be established with FNA-based cytology, and surgical excision is necessary for definitive diagnosis. Recent advances in genetic and molecular testing may increase the diagnostic accuracy of FNA in managing thyroid nodules.

New insights in risk stratification of differentiated thyroid cancer

PURPOSE OF REVIEW

Numerous staging and scoring systems exist for differentiated thyroid cancer (DTC), but all harbor limitations. This has prompted investigation for new factors with prognostic implications for DTC.

RECENT FINDINGS

Several new factors that may be involved in DTC risk stratification have emerged, such as thyroid stimulating hormone and molecular markers. In addition, others are controversial and being challenged, such as age, sex and lymph node involvement.

SUMMARY

The purpose of this review is to present recent updates in the literature on new potential risk stratification predictors for DTC.

TERT promoter mutations are a major indicator of poor outcome in differentiated thyroid carcinomas

CONTEXT

Telomerase promoter mutations (TERT) were recently described in follicular cell-derived thyroid carcinomas (FCDTC) and seem to be more prevalent in aggressive cancers.

OBJECTIVES

We aimed to evaluate the frequency of TERT promoter mutations in thyroid lesions and to investigate the prognostic significance of such mutations in a large cohort of patients with differentiated thyroid carcinomas (DTCs).

DESIGN

This was a retrospective observational study.

SETTING AND PATIENTS

We studied 647 tumors and tumor-like lesions. A total of 469 patients with FCDTC treated and followed in five university hospitals were included. Mean follow-up (±SD) was 7.8 ± 5.8 years.

MAIN OUTCOME MEASURES

Predictive value of TERT promoter mutations for distant metastasization, disease persistence at the end of follow-up, and disease-specific mortality.

RESULTS

TERT promoter mutations were found in 7.5% of papillary carcinomas (PTCs), 17.1% of follicular carcinomas, 29.0% of poorly differentiated carcinomas, and 33.3% of anaplastic thyroid carcinomas. Patients with TERT-mutated tumors were older (P < .001) and had larger tumors (P = .002). In DTCs, TERT promoter mutations were significantly associated with distant metastases (P < .001) and higher stage (P < .001). Patients with DTC harboring TERT promoter mutations were submitted to more radioiodine treatments (P = .009) with higher cumulative dose (P = .004) and to more treatment modalities (P = .001). At the end of follow-up, patients with TERT-mutated DTCs were more prone to have persistent disease (P = .001). TERT promoter mutations were significantly associated with disease-specific mortality [in the whole FCDTC (P < .001)] in DTCs (P < .001), PTCs (P = .001), and follicular carcinomas (P < .001). After adjusting for age at diagnosis and gender, the hazard ratio was 10.35 (95% confidence interval 2.01-53.24; P = .005) in DTC and 23.81 (95% confidence interval 1.36-415.76; P = .03) in PTCs.

CONCLUSIONS

TERT promoter mutations are an indicator of clinically aggressive tumors, being correlated with worse outcome and disease-specific mortality in DTC. TERT promoter mutations have an independent prognostic value in DTC and, notably, in PTC.

Prognostic biomarkers in thyroid cancer

Thyroid carcinomas represent a challenging problem from the prognostic standpoint. Despite an overall good prognosis of the most frequent endocrine malignancy, 10-15 % of papillary thyroid carcinomas (PTCs) turn refractory to radioactive iodine therapy. The increased incidence of thyroid cancer has led to the search for solid prognostic biomarkers that predict the behaviour of these tumours. Clinical and histopathological prognostic factors remain the only safe elements to be used for diagnosis and prognosis of patients with thyroid tumours. Despite the huge amount of genetic information of thyroid tumours, very few new markers revealed diagnostic or prognostic value per se. BRAF mutation can have some value if associated to other clinico-pathological parameters, or in the particular setting of iodine refractory tumours. Others can prove interesting in the future as predictive biomarkers of therapeutic response, but more studies are needed to confirm these potential biomarkers.

Genetic alterations in thyroid tumors from patients irradiated in childhood for tinea capitis treatment

OBJECTIVE

Exposure to ionizing radiation at young age is the strongest risk factor for the occurrence of papillary thyroid carcinoma (PTC). RET/PTC rearrangements are the most frequent genetic alterations associated with radiation-induced PTC, whereas BRAF and RAS mutations and PAX8-PPARG rearrangement have been associated with sporadic PTC. We decided to search for such genetic alterations in PTCs of patients subjected in childhood to scalp irradiation.

DESIGN

We studied 67 thyroid tumors from 49 individuals irradiated in childhood for tinea capitis scalp epilation: 36 malignant (12 cases of conventional PTC (cPTC), two cPTC metastases, 20 cases of follicular variant PTC (FVPTC), one oncocytic variant of PTC and one follicular carcinoma) and 31 follicular thyroid adenomas.

METHODS

The lesions were screened for the BRAF(V600E) and NRAS mutations and for RET/PTC and PAX8-PPARG rearrangements.

RESULTS

BRAF(V600E) mutation was detected in seven of 14 (50%) cPTC and two of 20 FVPTC (10%) (P=0.019). NRAS mutation was present in one case of FVPTC (5%). RET/PTC1 rearrangement was found, by RT-PCR, in one of 17 cases (5.9%) and by fluorescence in situ hybridization in two of six cases (33%). PAX8-PPARG rearrangement was not detected in any carcinoma. None of the follicular adenomas presented any of the aforementioned genetic alterations.

CONCLUSIONS

The prevalence of BRAF(V600E) mutation in our series is the highest reported in series of PTCs arising in radiation-exposed individuals. The prevalence of RET/PTC1 rearrangement fits with the values recently described in a similar setting.

Survey of 548 oncogenic fusion transcripts in thyroid tumors supports the importance of the already established thyroid fusions genes

Neoplasms frequently present structural chromosomal aberrations that can alter the level of expression of a protein or to the expression of an aberrant chimeric protein. In the thyroid, the PAX8-PPARG fusion is present in the neoplastic lesions that have a follicular architecture-follicular thyroid carcinoma (FTC) and follicular variant of papillary thyroid carcinoma (FVPTC), and less frequently in follicular thyroid adenoma (FTA), while the presence of RET/PTC fusions are largely restricted to papillary thyroid carcinoma (PTC). The ability to detect fusion genes is relevant for a correct diagnosis and for therapy. We have developed a new fusion gene microarray-based approach for simultaneous analysis of all known and predicted fusion gene variants. We did a comprehensive screen for 548 known and putative fusion genes in 27 samples of thyroid tumors and three positive controls-one thyroid cancer cell line (TPC-1) and two PTCs with known CCDC6-RET (alias RET/PTC1) fusion gene, using this microarray. Within the thyroid tumors tested, only well known, previously reported fusion genes in thyroid oncology were identified. Our results reinforce the pathogenic role played by RET/PTC1, RET/PTC3, and PAX8-PPARG fusion genes in thyroid tumorigenesis.