Changes in the clinicopathological characteristics and genetic alterations of follicular thyroid cancer

Association of Ultrasonography Features of Follicular Thyroid Carcinoma With Tumor Invasiveness and Prognosis Based on WHO Classification and TERT Promoter Mutation

OBJECTIVE

To investigate the association of ultrasound (US) features of follicular thyroid carcinoma (FTC) with tumor invasiveness and prognosis based on the World Health Organization (WHO) classification and telomerase reverse transcriptase (TERT) promoter mutations.

MATERIALS AND METHODS

This retrospective study included 54 surgically confirmed FTC patients with US images and TERT promoter mutations (41 females and 13 males; median age [interquartile range], 40 years [30-51 years]). The WHO classification consisted of minimally invasive (MI), encapsulated angioinvasive (EA), and widely invasive (WI) FTCs. Alternative classifications included Group 1 (MI-FTC and EA-FTC with wild type TERT), Group 2 (WI-FTC with wild type TERT), and Group 3 (EA-FTC and WI-FTC with mutant TERT). Each nodule was categorized according to the US patterns of the Korean Thyroid Imaging Reporting and Data System (K-TIRADS) and American College of Radiology-TIRADS (ACR-TIRADS). The Jonckheere-Terpstra and Cochran-Armitage tests were used for statistical analysis.

RESULTS

Among 54 patients, 29 (53.7%) had MI-FTC, 16 (29.6%) had EA-FTC, and nine (16.7%) had WI-FTC. In both the classifications, lobulation, irregular margins, and final assessment categories showed significant differences (all Ps ≤ 0.04). Furthermore, the incidences of lobulation, irregular margin, and high suspicion category tended to increase with increasing tumor invasiveness and worse prognosis (all Ps for trend ≤ 0.006). In the WHO groups, hypoechogenicity differed significantly among the groups (P = 0.01) and tended to increase in proportion as tumor invasiveness increased (P for trend = 0.02). In the alternative group, punctate echogenic foci were associated with prognosis (P = 0.03, P for trend = 0.03).

CONCLUSION

Increasing tumor invasiveness and worsening prognosis in FTC based on the WHO classification and TERT promoter mutation results were positively correlated with US features that indicate malignant probability according to both K-TIRADS and ACR-TIRADS.

DICER1 tumor predisposition syndrome: an evolving story initiated with the pleuropulmonary blastoma

DICER1 syndrome (OMIM 606241, 601200) is a rare autosomal dominant familial tumor predisposition disorder with a heterozygous DICER1 germline mutation. The most common tumor seen clinically is the pleuropulmonary blastoma (PPB), a lung neoplasm of early childhood which is classified on its morphologic features into four types (IR, I, II and III) with tumor progression over time within the first 4-5 years of life from the prognostically favorable cystic type I to the unfavorable solid type III. Following the initial report of PPB, its association with other cystic neoplasms was demonstrated in family studies. The detection of the germline mutation in DICER1 provided the opportunity to identify and continue to recognize a number seemingly unrelated extrapulmonary neoplasms: Sertoli-Leydig cell tumor, gynandroblastoma, embryonal rhabdomyosarcomas of the cervix and other sites, multinodular goiter, differentiated and poorly differentiated thyroid carcinoma, cervical-thyroid teratoma, cystic nephroma-anaplastic sarcoma of kidney, nasal chondromesenchymal hamartoma, intestinal juvenile-like hamartomatous polyp, ciliary body medulloepithelioma, pituitary blastoma, pineoblastoma, primary central nervous system sarcoma, embryonal tumor with multilayered rosettes-like cerebellar tumor, PPB-like peritoneal sarcoma, DICER1-associated presacral malignant teratoid neoplasm and other non-neoplastic associations. Each of these neoplasms is characterized by a second somatic mutation in DICER1. In this review, we have summarized the salient clinicopathologic aspects of these tumors whose histopathologic features have several overlapping morphologic attributes particularly the primitive mesenchyme often with rhabdomyoblastic and chondroid differentiation and an uncommitted spindle cell pattern. Several of these tumors have an initial cystic stage from which there is progression to a high grade, complex patterned neoplasm. These pathologic findings in the appropriate clinical setting should serve to alert the pathologist to the possibility of a DICER1-associated neoplasm and initiate appropriate testing on the neoplasm and to alert the clinician about the concern for a DICER1 mutation.

Radioiodine Refractory Follicular Thyroid Cancer and Surgery for Cervical Relapse

Compared to its more common counterpart papillary thyroid cancer (PTC), follicular thyroid cancer (FTC) has a less favorable outcome, due to its higher incidence of distant metastases and advanced stages at diagnosis. Despite radioiodine (RAI) avidity, metastatic FTC often progresses after radioiodine treatment (RAIT). We aimed at evaluating the indications and outcomes of surgery for cervical relapse of radioiodine refractory FTC. Patients receiving RAIT between 2005 and 2015 at the University Hospital of Cologne, Germany, were screened. Patients with FTC were identified. Demographics, clinic-pathologic characteristics, treatment, and outcome of patients diagnosed with RAI refractory FTC, who underwent cervical surgery in the course of disease, were analyzed. FTC accounted for 8.8% of all thyroid carcinomas undergoing RAIT. In 35.2% of FTC patients, disease persisted or recurred despite a cumulative mean RAI activity of 18.7 GBq ± 11.6 (follow-up 83.5 ± 56.7 months). Distant metastases were diagnosed in 75% of these patients, as bone (57.6%), lung (54.6%), and liver metastases (12.1%). Cervical relapse occurred in 63.6% of these patients and was treated in 57.1% with surgery with, and without, external beam radiation therapy (EBRT). Despite surgery and EBRT, in 75% of patients, cervical relapse recurred again. In conclusion, surgery for cervical radioiodine refractory FTC relapse is often performed in metastatic setting. With and without EBRT, cure is rare, although metastases can appear radioiodine avid. Early biological marker and systemic treatments for these patients are still needed.

Molecular Pathology of Non-familial Follicular Epithelial-Derived Thyroid Cancer in Adults: From RAS/BRAF-like Tumor Designations to Molecular Risk Stratification

This review addresses the impact of molecular alterations on the diagnosis and prognosis of differentiated thyroid carcinoma (DTC), including papillary, follicular, and well-differentiated carcinoma NOS, as well as oncocytic neoplasms. The molecular characterization of DTC is based upon the well-established dichotomy of BRAF-like and RAS-like designations, together with a remaining third group, less homogeneous, composed of non-BRAF-/non-RAS-like tumors. The role of BRAF V600E mutation in risk stratification is discussed in the clinico-pathological context, namely, staging and invasive features of classic papillary thyroid carcinoma (PTC) and histopathological variants carrying an excellent prognosis (microPTC) or a guarded prognosis, including the aggressive variants tall cell and hobnail cell PTCs. In follicular patterned tumors, namely, follicular thyroid carcinoma (FTC), with or without oncocytic features, the most prevalent molecular alteration are RAS mutations that do not carry prognostic significance. The only genetic alteration that has been proven to play a role in risk stratification of PTC and FTC is TERT promoter (TERTp) mutation.

The Coexistence of Genetic Mutations in Thyroid Carcinoma Predicts Histopathological Factors Associated With a Poor Prognosis: A Systematic Review and Network Meta-Analysis

PURPOSE

Genetic mutations may play an important role in the progression and invasion of thyroid carcinoma (TC), and their coexistence may result in mutational synergy. The presence of the BRAFV600E mutation, as well as mutations affecting the TERT promoter, RAS, CHEK2 and RET/PTC, may all have an impact on prognosis. The aim of this study was to explore whether synergy between the coexistent mutations predicts histopathological prognostic factors that influence disease outcome.

METHODS

A comprehensive literature search of PubMed, Embase and the Cochrane Library, from their inception until January 2020. Primary outcomes included: disease stage, lymph node metastasis, extrathyroidal extension and distant metastasis; while, secondary outcomes included: tumor recurrence, mortality, invasion of thyroid capsule, multiplicity, presented as an odds ratio (OR) with 95% credible intervals (CrI).

RESULTS

27 publications (comprising 9 active intervention arms), involving 8,388 TC patients, were selected. Network meta-analytic estimates of active interventions contrasted with other active interventions, with random effects, were calculated. In terms of outcomes focus on overall TC, BRAFV600E + TERT co-mutation ranked highest for diseases stage (OR = 5.74, 95% CrI: 3.09-10.66), as well as lymph node metastasis, extrathyroidal extension (5.74, 4.06-8.10), tumor recurrence (7.21, 3.59-14.47), and invasion of the thyroid capsule (3.11, 1.95-4.95). BRAFV600E + TERT co-mutation ranked secondary in distant metastasis, mortality, and multiplicity that ranked highest was TERT+RAS or RAS. When we were limited to the study of patients with papillary TC (PTC), BRAFV600E + TERT always ranked highest for primary outcomes: disease stage (6.39, 3.13-13.04), lymph node metastasis, extrathyroidal extension (5.80,3.89-8.64) and distant metastasis (7.33, 3.00-17.89), while BRAFV600E + TERT again ranked highest in secondary outcomes: tumor recurrence (7.23,3.37-15.51), mortality (9.26, 3.02-28.42), invasion of thyroid capsule (3.20,2.01-5.11), and multiplicity.

CONCLUSIONS

In this molecular marker mutation-based systematic review and network meta-analysis, we found that coexistent BRAFV600E + TERT genetic co-mutations predicted poor histopathological prognosis, including progression, invasion, and metastasis, especially in PTC. For the overall TC, the BRAFV600E + TERT + RAS triple mutations may have a greater impact on the prognosis, and further research should related to potentially important features. This study is registered with PROSPERO, number CRD42019143242.

Genetic differences in follicular thyroid carcinoma between Asian and Western countries: a systematic review

Thyroid cancer is the most common endocrine malignancy, and follicular thyroid carcinoma (FTC) is the second most common thyroid cancer following papillary thyroid carcinoma (PTC). RAS mutation and PAX8/PPARγ rearrangement are the two representative genetic alterations in FTC, and there are studies from various countries on their regional frequencies. In this study, we systematically reviewed all available literature aiming to create a complete global map showing the frequencies of these common oncogenic drivers in FTC and to highlight the trends in Asian and Western countries. We performed a search in two electronic databases and identified 71 studies that fit our criteria from 1,329 studies found with our database search terms. There were 54 articles with 1,143 FTC patients and 39 articles with 764 FTC patients available for calculating the frequency of RAS mutation and PAX8/PPARγ rearrangement, respectively. NRAS mutation was the most frequent RAS mutation in all regions, followed by HRAS and KRAS mutation. The frequency of RAS mutation in Asian countries was higher than Western countries (34% vs. 27%, P=0.006) when the mutation detection method was not taken into account. In contrast, this difference in RAS mutation incidence between Asian and Western countries (28% vs. 25%, P=0.47) did not show up in our subgroup analysis incorporating only studies using direct sequencing method. The reported difference of RAS mutation frequency in the previous literature might not be due to the true prevalence of RAS mutation. They could be attributed to the difference in the detection method. As to PAX8/PPARγ rearrangement, Western countries overall had a much higher prevalence than Asian countries (23% vs. 4%, P<0.001), but some European countries had a low incidence, implying regional heterogeneity of PAX8/PPARγ rearrangement. A substantial lack of mutation data in FTC was found in several regions of the world such as Central Asia, Middle East, Africa, and Central and South America. Our results provide the most comprehensive global status of representative genetic alterations in FTC and highlight the similarities and differences between Asian and Western countries.

Predominant DICER1 Pathogenic Variants in Pediatric Follicular Thyroid Carcinomas

Background: Pediatric thyroid cancer has characteristics that are distinct from adulthood thyroid cancer. Due to its very low prevalence, little is known about the genetic characteristics of pediatric follicular thyroid cancer (FTC). Methods: We investigated genetic alterations in tumor tissues from 15 patients aged <20 years (median: 14.3 years; range: 2.4 - 19.0 years) using multifaceted approaches. Whole-exome sequencing, targeted next-generation sequencing using a cancer gene panel, and Sanger sequencing of the major exons of the H/K/N-RAS and DICER1 genes and the promoter region of the TERT gene were performed. Normal tissues or blood of patients with DICER1- or PTEN-positive tumors was also evaluated to determine whether the variant is germ line. Results: The median tumor size was 3.1 cm (range: 0.6 - 6.4 cm). Four patients exhibited angioinvasion and one extensive capsular invasion; none showed evidence of disease over a median of 8.1 years. Eight patients (53.3%) had DICER1 variants, including four with DICER1 syndrome (three patients were <10 years of age). One patient had a germ line PTEN frameshift variant with the diagnosis of PTEN hamartoma tumor syndrome. One patient had a PAX8/PPARγ rearrangement, and two patients had no genetic driver alteration other than multiple loss of heterozygosity with or without copy number alterations in their tumors. No RAS or TERT variants were found. Nodular hyperplasia and follicular adenoma (FA) coexisted in DICER1 variant-positive FTCs more frequently than variant-negative FTCs (p = 0.026). All DICER1 variant-positive FTCs had a somatic missense variant at metal binding sites (six at codon p.E1813 and two at codon p.D1709) within the RNase IIIb domain; seven had other missense, nonsense, or frameshift variants in the DICER1 gene. Six coexisting FAs of two patients with DICER1 syndrome (three of each) had additional somatic variants at metal binding sites within the RNase IIIb domain (codon p.E1705, p.D1709, p.D1810, or p.E1813), different from each other and from the indexed FTC tumor. Conclusions: Pediatric FTCs have distinct genomic alterations and pathogenesis compared with adults, particularly those characterized by DICER1 variants. The DICER1 variant should be considered in pediatric FTCs, especially in cases <10 years of age. In all DICER1 variant-positive FTCs and FAs, recurrent hotspot variants were found at metal binding sites within the RNase IIIb domain, suggesting they impact tumorigenesis.

Utilities of RAS Mutations in Preoperative Fine Needle Biopsies for Decision Making for Thyroid Nodule Management: Results from a Single-Center Prospective Cohort

Background: It has been advocated to apply individualized strategies to evaluate thyroid nodules due to the growing awareness that the pathogenesis of thyroid cancer is not uniform. Molecular markers in fine needle biopsies (FNBs) may be helpful for the diagnosis and management decisions. Unlike the detection of BRAF mutations, the clinical utility of rat sarcoma viral oncogene homolog (RAS) mutations has not been fully elucidated. This study aimed at presenting a real-world performance of RAS mutations in identifying thyroid malignancies, at investigating the nature of thyroid tumors carrying RAS mutations, and at providing an additional reference for interpreting how to utilize the presence of RAS mutations in the decision-making process of thyroid nodule management. Methods: Between February 2015 and December 2017, 1400 sequential thyroid biopsies were performed at Boston Medical Center. Of these, 546 FNBs were evaluated for RAS mutations by using a ThyroSeq next-generation sequencing panel. Nodules carrying RAS mutations were prospectively followed, and medical records were collected. Results: ThyroSeq successfully provided molecular information in 504 nodules; 173 with molecular alteration(s); and 80 positive for mutations in the Kirsten-, Neuroblastoma-, or Harvey-RAS genes. RAS gene mutations constituted up to 46.2% of the total molecular alterations found in the study. Fifty-six of the 80 RAS-positive nodules underwent surgery, 33 (58.9%) were confirmed to be benign, 7 (12.5%) were noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP), and 16 (28.6%) were thyroid carcinomas. The positive predictive value, negative predictive value, and accuracy of RAS mutations for identifying malignancies among cytologically indeterminate nodules were 25.5%, 89.7%, and 54.0% when NIFTP was not counted as cancer. A combination of RAS and other mutations increased the risk of malignancy. Twelve histopathologically proved RAS-only-positive malignant nodules all showed low-risk features and favorable prognosis. RAS isoforms added little assistance for predicting a malignancy and the response to therapy in our series. Conclusions:RAS mutations represent the most frequently detected genetic alterations in our series. RAS mutations, when occurring alone, are not helpful markers to identify malignancy among Bethesda III/IV cytologies, but may predict favorable behavior, and hence should be considered to guide initial management.

Association between TERT promoter mutations and clinical behaviors in differentiated thyroid carcinoma: a systematic review and meta-analysis

BACKGROUND

The association between telomerase reverse transcriptase (TERT) promoter mutations and some clinical behaviors in thyroid cancer remains controversial and requires additional investigation. This study aimed to evaluate the association between TERT promoter mutations and clinical behaviors (including clinicopathological features and prognosis) in differentiated thyroid carcinomas (DTC).

METHODS

We performed an up-to-date systematic review and current comprehensive meta-analysis. We searched three electronic databases for relevant studies. We used fixed- or random-effect models to calculate pooled estimated odds ratios (ORs) or standardized mean differences (SMDs) and corresponding 95% confidence intervals (CIs).

RESULTS

We included 51 eligible studies incorporating 11,382 cases. Average frequencies of TERT promoter mutations in DTC, papillary (PTC), and follicular (FTC) thyroid carcinomas were 10.9%, 10.6%, and 15.1%, respectively. In DTC and PTC, TERT promoter mutations were significantly associated with sex, age, tumor size, vascular invasion, extrathyroidal extension, lymph node and distant metastases, advanced tumor, nodes, and metastasis (TNM) stage, persistence/recurrence, and disease-specific mortality. In FTC, TERT promoter mutations were significantly associated with age, distant metastases, advanced TNM stage, persistence/recurrence, and disease-specific mortality.

CONCLUSIONS

TERT promoter mutations could be considered as biomarkers assisting in risk stratification, prognostic prediction, and individualizing therapeutic options for DTC (PTC and FTC).

Differences in Mutational Profile between Follicular Thyroid Carcinoma and Follicular Thyroid Adenoma Identified Using Next Generation Sequencing

We aimed to identify differences in mutational status between follicular thyroid adenoma (FTA) and follicular thyroid cancer (FTC). The study included 35 patients with FTA and 35 with FTC. DNA was extracted from formalin-fixed paraffin-embedded (FFPE) samples from thyroidectomy. Next-generation sequencing (NGS) was performed with the 50-gene Ion AmpliSeq Cancer Hotspot Panel v2. Potentially pathogenic mutations were found in 14 (40%) FTA and 24 (69%) FTC patients (OR (95%CI) = 3.27 (1.22−8.75)). The number of mutations was higher in patients with FTC than FTA (p-value = 0.03). SMAD4 and STK11 mutations were present only in patients with FTA, while defects in FBXW7, JAK3, KIT, NRAS, PIK3CA, SMARCB1, and TP53 were detected exclusively in FTC patients. TP53 mutations increased the risk of FTC; OR (95%CI) = 29.24 (1.64–522.00); p-value = 0.001. FLT3-positivity was higher in FTC than in the FTA group (51.4% vs. 28.6%; p-value = 0.051). The presence of FLT3 and TP53 with no RET mutations increased FTC detectability by 17.1%, whereas the absence of FLT3 and TP53 with a presence of RET mutations increased FTA detectability by 5.7%. TP53 and FLT3 are candidate markers for detecting malignancy in follicular lesions. The best model to predict FTA and FTC may consist of FLT3, TP53, and RET mutations considered together.

Mutation profiles of follicular thyroid tumors by targeted sequencing

BACKGROUND

One of the major challenges remaining in the classification of thyroid tumor is the determination of whether a nodule is benign or malignant. We aimed to characterize the mutational profiles of follicular thyroid tumor and to identify markers with potential diagnostic and prognostic implications.

METHODS

Targeted sequencing with a panel of 18 thyroid cancer-related genes was performed on 48 tissue samples from follicular thyroid adenoma (FTA), 32 follicular tumors of uncertain malignant potential (FT-UMP), 17 well-differentiated tumors of uncertain malignant potential (WDT-UMP) and 53 samples from follicular thyroid carcinoma (FTC). The correlation of mutation profiles and clinicopathological features and prognosis were also analyzed.

RESULTS

We identified 95 nonsilent mutations spanning 14 genes. Specifically, TERT promoter (TERTp) mutations were exclusively detected in FTC. A total of 80% EIF1AX exon 2 mutations (4/5) and 75% TSHR mutations (3/4) occurred in FTA, whereas the rest of them occurred in FT-UMP. KRAS mutations and TP53 mutations were only presented in borderline or malignant tumors. H/N-RAS mutations were detected in all four subtypes, but were most commonly found in WDT-UMP (p = 0.031). All N-RAS mutations were located at codon 61. BRAF V600E and RET fusion were absent in the entire cohort. In FTC cases, EIF1AX mutations were all located at intron 5/exon 6 and correlated with advanced disease (p = 0.032). Both EIF1AX and TERTp mutations predicted shorter disease-free survival (p = 0.007, p = 0.024, respectively). Further analysis revealed that TERTp mutations were correlated with shorter disease-free survival in patients with minimally invasive /encapsulated angioinvasive FTC (p = 0.017), but not in those with widely invasive FTC (p = 0.297).

CONCLUSION

TERTp, EIF1AX, TSHR, H/N/K-RAS and TP53 mutations may have diagnostic or prognostic potential in follicular thyroid tumors. TERTp mutations may predict a poor outcome in patients with minimally invasive/encapsulated angioinvasive FTC.

Genomic Characterization of Differentiated Thyroid Carcinoma

Since the release of The Cancer Genome Atlas study of papillary thyroid carcinoma (PTC) in 2014, additional genomic studies of differentiated thyroid carcinoma (DTC) using massively-parallel sequencing (MPS) have been published. Recent advances in MPS technology have started to provide important insights into the molecular pathogenesis of DTC. In the genomic landscape, the most recurrently altered genes in DTC, which has a low mutational burden relative to other cancers, are BRAF, RAS, and fusion genes. Some novel driver candidates also have been identified. The frequency of these genomic alterations varies across the subtypes of DTC (classical PTC, follicular variant of PTC, and follicular thyroid carcinoma). Telomerase reverse transcriptase (TERT) promoter mutations are the alteration that makes the most important contribution to the progression of DTC. In the transcriptomic landscape, DTC can be classified according to its gene expression profile, and each subtype has a distinct mutational profile, intracellular signaling output, and clinicopathological characteristics. Herein, we review the results of genomic studies using MPS technology, and describe the types and frequencies of genomic alterations according to histological classifications of DTC and the characteristics and significance of the gene expression signatures of DTC.

IAPs cause resistance to TRAIL-dependent apoptosis in follicular thyroid cancer

Follicular thyroid cancer's (FTC) excellent long-term prognosis is mainly dependent on postoperative radioactive iodine (RAI) treatment. However, once the tumour becomes refractory, the 10-year disease-specific survival rate drops below 10%. The aim of our study was to evaluate the prognostic and biological role of the TRAIL system in FTC and to elucidate the influence of small-molecule-mediated antagonisation of inhibitor of apoptosis proteins (IAPs) on TRAIL sensitivity in vitro Tissue microarrays were constructed from forty-four patients with histologically confirmed FTC. Expression levels of TRAIL and its receptors were correlated with clinicopathological data and overall as well as recurrence-free survival. Non-iodine-retaining FTC cell lines TT2609-bib2 and FTC133 were treated with recombinant human TRAIL alone and in combination with Smac mimetics GDC-0152 or Birinapant. TRAIL-R2/DR5 as well as TRAIL-R3/DcR1 and TRAIL-R4/DcR2 were significantly higher expressed in advanced tumour stages. Both decoy receptors were negatively associated with recurrence-free and overall survival. TRAIL-R4/DcR2 additionally proved to be an independent negative prognostic marker in FTC (HR = 1.446, 95% CI: 1.144-1.826; P < 0.001). In vitro, the co-incubation of Birinapant or GDC-0152 with rh-TRAIL-sensitised FTC cell lines for TRAIL-induced apoptosis, through degradation of cIAP1/2. The TRAIL system plays an important role in FTC tumour biology. Its decoy receptors are associated with poor prognosis as well as earlier recurrence. The specific degradation of cIAP1/2 sensitises FTC cells to TRAIL-induced apoptosis and might highlight a new point of attack in patients with RAI refractory disease.