The ret/PTC mutations are common in sporadic papillary thyroid carcinoma of children and young adults

Historical context, process, and development trends of pediatric thyroid cancer research: a bibliometric analysis

Objective

At present, the structure of knowledge in the field of childhood thyroid cancer is not clear enough, and scholars lack a sufficient understanding of the developing trends in this field, which has led to a shortage of forward-looking outputs. The purpose of this research is to help scholars construct a complete knowledge framework and identify current challenges, opportunities, and development trends.

Methods

We searched the literature in the Web of Science Core Collection database on August 7, 2023 and extracted key information from the top 100 most cited articles, such as the countries, institutions, authors, themes, and keywords. We used bibliometric tools such as bibliometrix, VOSviewer, and CiteSpace for a visualization analysis and Excel for statistical descriptions.

Results

The top 100 most cited articles fluctuated over time, and the research was concentrated in European countries, the United States, and Japan, among which scientific research institutions and scholars from the United States made outstanding contributions. Keyword analysis revealed that research has shifted from simple treatment methods for pediatric thyroid cancer (total thyroidectomy) and inducing factors (the Chernobyl power station accident) to the clinical applications of genetic mutations (such as the BRAF and RET genes) and larger-scale genetic changes (mutation studies of the DICER1 gene). The thematic strategy analysis showed an increasing trend towards the popularity of fusion oncogenes, while the popularity of research on traditional treatments and diagnostics has gradually declined.

Conclusion

Extensive research has been conducted on the basic problems of pediatric thyroid cancer, and there has been significant outputs in the follow-up and cohort analysis of conventional diagnostic and treatment methods. However, these methods still have certain limitations. Therefore, scholars should focus on exploring fusion genes, the clinical applications of molecular targets, and novel treatment methods. This study provides a strong reference for scholars in this field.

Management of Advanced Medullary Thyroid Carcinoma: Current Systemic Therapy Options

The current rapid development of more selective and effective drugs for the treatment of thyroid cancer has open a new era in the treatment of patients with this condition, in the past limited to the possibility of only radioactive iodine for well differentiated tumor and surgery for medullary thyroid carcinoma (MTC). The treatment of advanced medullary thyroid carcinoma has evolved in the last few years and options for patients with advanced disease are now available. Multikinase inhibitors (MKIs) with nonselective RET inhibition like Vandetanib and Cabozantinib were approved for the treatment of MTC, although the efficacy is limited due to the lack of specificity resulting in a higher rate of drug-related adverse events, leading to subsequent dose reductions, or discontinuation, and the development of a resistance mechanism like seen on the RET Val804 gatekeeper mutations. MTC is associated with mutations in the RET protooncogene, and new highly selective RET inhibitors have been developed including Selpercatinib and Pralsetinib, drugs that have demonstrate excellent results in clinical trials, and efficacy even in the presence of gatekeeper mutations. However, despite their efficacy and great tolerability, mechanisms of resistance have been described, such as the RET solvent front mutations. Due to this, the need of constant evolution and drug research is necessary to overcome the emergence of resistance mechanisms.

Primary presentation and clinical course of pediatric and adolescent patients with differentiated thyroid carcinoma after radioiodine therapy

Introduction

Differentiated thyroid carcinoma (DTC) in childhood and during adolescence is extremely rare. Pediatric DTC commonly presents with advanced disease at diagnosis including a high prevalence of cervical lymph node metastases and pulmonary metastases. Studies in children with DTC are limited. Therefore, we aimed to evaluate the initial presentation, effectiveness of radioiodine therapy (RIT), and long-term outcome of prepubertal in comparison to pubertal/postpubertal patients.

Methods

Eighty-five pediatric and young patients aged 6.4 to 21.9 years with histopathologically confirmed DTC were retrospectively included. They all underwent total thyroidectomy followed by RIT. Initial presentation and outcome of prepubertal and pubertal/postpubertal patients were compared 1 year after RIT, during follow-up, and at the last visit of follow-up.

Results

Prepubertal patients presented with significantly higher T and M stages. One year after RIT, 42/81 (52%) patients still presented with evidence of disease (ED). During follow-up of a median of 7.9 years, prepubertal patients were less often in complete remission (58% vs. 82% in pubertal patients). At the last visit of follow-up, 19/80 (24%) patients still had ED without statistical differences between the two groups (42% prepubertal vs. 18% pubertal/postpubertal, p-value 0.06). None of our patients died disease-related over the observed period.

Conclusion

Prepubertal children with DTC presented with a more advanced tumor stage at the initial presentation. During follow-up, they present more often with ED. However, at the end of our study, we did not observe statistically relevant differences in patient outcomes between the prepubertal and pubertal/postpubertal groups.

Genomic landscape of sporadic pediatric differentiated thyroid cancers: a systematic review and meta-analysis

OBJECTIVES

Differentiated thyroid cancers (DTCs) in the paediatric population differ from that of their adult counterparts in terms of clinicopathological characteristics and treatment outcomes. This systematic review and meta-analysis was conducted to comprehensively evaluate the prevalence of various genetic alterations underlying the pathogenesis of sporadic paediatric DTCs.

METHODS

This study followed the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) guidelines. Systematic searches were made on the PubMed and Embase databases using relevant keywords, and articles published until October 15, 2021 were selected. Data on the prevalence of various genetic alterations were extracted from the individual articles. Random-effects model was employed for meta-analysis to generate pooled estimates and their 95% confidence intervals (95% CIs).

RESULTS

Thirty-three articles comprising 1,380 paediatric patients were included. RET rearrangement (pooled prevalence: 24.4%, 95% CI: 19.1-30.1) was observed to be the most common genetic alteration in sporadic paediatric DTCs, closely followed by BRAF point mutation (pooled prevalence: 21.2%, 95% CI: 17.2-25.5). Other common alterations included: NTRK rearrangement (pooled prevalence: 13.5%, 95% CI: 9.5-17.9) and DICER1 mutation (pooled prevalence: 12.5%, 95% CI: 3.6-25.7). RAS and TERT mutations were observed to be relatively uncommon (pooled prevalence: 5.7%, 95% CI: 2.9-9.3, and 2.2%, 95% CI: 0.4-5.5, respectively). There was no evidence of publication bias.

CONCLUSIONS

Fusion oncogenes are noted to be the major oncogenic drivers in sporadic paediatric DTCs and underlie their unique behaviour. However, despite the relatively lower frequency of BRAF point mutation compared to adults, it remains a major player in childhood DTCs.

Major Oncogenic Drivers and Their Clinicopathological Correlations in Sporadic Childhood Papillary Thyroid Carcinoma in Belarus

Childhood papillary thyroid carcinoma (PTC) diagnosed after the Chernobyl accident in Belarus displayed a high frequency of gene rearrangements and low frequency of point mutations. Since 2001, only sporadic thyroid cancer occurs in children aged up to 14 years but its molecular characteristics have not been reported. Here, we determine the major oncogenic events in PTC from non-exposed Belarusian children and assess their clinicopathological correlations. Among the 34 tumors, 23 (67.6%) harbored one of the mutually exclusive oncogenes: 5 (14.7%) BRAFV600E, 4 (11.8%) RET/PTC1, 6 (17.6%) RET/PTC3, 2 (5.9%) rare fusion genes, and 6 (17.6%) ETV6ex4/NTRK3. No mutations in codons 12, 13, and 61 of K-, N- and H-RAS, BRAFK601E, or ETV6ex5/NTRK3 or AKAP9/BRAF were detected. Fusion genes were significantly more frequent than BRAFV600E (p = 0.002). Clinicopathologically, RET/PTC3 was associated with solid growth pattern and higher tumor aggressiveness, BRAFV600E and RET/PTC1 with classic papillary morphology and mild clinical phenotype, and ETV6ex4/NTRK3 with follicular-patterned PTC and reduced aggressiveness. The spectrum of driver mutations in sporadic childhood PTC in Belarus largely parallels that in Chernobyl PTC, yet the frequencies of some oncogenes may likely differ from those in the early-onset Chernobyl PTC; clinicopathological features correlate with the oncogene type.

Concomitant Pathogenic Mutations and Fusions of Driver Oncogenes in Tumors

Driver oncogene alterations have always been one of leading causes in the process of occurrence and development of tumors. And the effects of driver oncogene alterations on tumorigenesis and progression in different kinds of tumors have been studied heatedly. And the roles that the driver oncogenes alterations play have been elucidated clearly in previous studies. The phenomenon of concomitant driver oncogenes mutations and driver genes fusions has gained much concentration in the past two decades. And a growing number of studies reported this phenomenon, either coexistence or mutually exclusivity. Here we reviewed on the phenomenon of concomitant mutations in three common types of carcinomas—lung cancer, thyroid cancer, and leukemia, which have been studied relatively more detailed and more general compared with others.

Management of pediatric differentiated thyroid cancer: An overview for the pediatric oncologist

Differentiated thyroid cancer (DTC) is the most common childhood thyroid malignancy. The standard of care for pediatric DTC is total thyroidectomy followed by radioactive iodine (RAI) treatment when indicated. Molecular changes and potential therapeutic targets have been recently described in pediatric thyroid cancer. Pediatric oncologists are increasingly involved in the evaluation of thyroid nodules in childhood cancer survivors and in the management of advanced thyroid cancer. In 2015, the American Thyroid Association published management guidelines for children with DTC. We provide an overview of the current standard of care and highlight available targeted therapies for progressive or RAI refractory DTC.

RET Gene Fusions in Malignancies of the Thyroid and Other Tissues

Following the identification of the BCR-ABL1 (Breakpoint Cluster Region-ABelson murine Leukemia) fusion in chronic myelogenous leukemia, gene fusions generating chimeric oncoproteins have been recognized as common genomic structural variations in human malignancies. This is, in particular, a frequent mechanism in the oncogenic conversion of protein kinases. Gene fusion was the first mechanism identified for the oncogenic activation of the receptor tyrosine kinase RET (REarranged during Transfection), initially discovered in papillary thyroid carcinoma (PTC). More recently, the advent of highly sensitive massive parallel (next generation sequencing, NGS) sequencing of tumor DNA or cell-free (cfDNA) circulating tumor DNA, allowed for the detection of RET fusions in many other solid and hematopoietic malignancies. This review summarizes the role of RET fusions in the pathogenesis of human cancer.

Pediatric Thyroid Cancer in Europe: An Overdiagnosed Condition? A Literature Review

Thyroid neoplastic pathology is the most common form of cancer associated with radiation exposure. The most common histopathological type of thyroid carcinoma is the differentiated thyroid cancer (these include papillary and follicular type), which represents over 90% of all cases, especially affecting girls rather than boys. Although patients are diagnosed in advanced stages as compared to adults, the prognosis of the disease is very good, with a 30-year survival rate of over 95% but post-therapeutic morbidity remains quite high. The treatment is based in particular on the therapeutic guidelines for adults, but as children have some histopathological and genetic characteristics of thyroid cancer, as well as different initial clinical presentations, we decided to review the literature on this pathology among the pediatric population, focusing on cases in Europe. The major interest is the impact of the Chernobyl accident.

Broken by the Cut: A Journey into the Role of Topoisomerase II in DNA Fragility

DNA topoisomerase II (TOP2) plays a critical role in many processes such as replication and transcription, where it resolves DNA structures and relieves torsional stress. Recent evidence demonstrated the association of TOP2 with topologically associated domains (TAD) boundaries and CCCTC-binding factor (CTCF) binding sites. At these sites, TOP2 promotes interactions between enhancers and gene promoters, and relieves torsional stress that accumulates at these physical barriers. Interestingly, in executing its enzymatic function, TOP2 contributes to DNA fragility through re-ligation failure, which results in persistent DNA breaks when unrepaired or illegitimately repaired. Here, we discuss the biological processes for which TOP2 is required and the steps at which it can introduce DNA breaks. We describe the repair processes that follow removal of TOP2 adducts and the resultant broken DNA ends, and present how these processes can contribute to disease-associated mutations. Furthermore, we examine the involvement of TOP2-induced breaks in the formation of oncogenic translocations of leukemia and papillary thyroid cancer, as well as the role of TOP2 and proteins which repair TOP2 adducts in other diseases. The participation of TOP2 in generating persistent DNA breaks and leading to diseases such as cancer, could have an impact on disease treatment and prevention.

Thyroid Cancer in the Pediatric Population

Thyroid cancer is rare in the pediatric population, but thyroid carcinomas occurring in children carry a unique set of clinical, pathologic, and molecular characteristics. In comparison to adults, children more often present with aggressive, advanced stage disease. This is at least in part due to the underlying biologic and molecular differences between pediatric and adult thyroid cancer. Specifically, papillary thyroid carcinoma (which accounts for approximately 90% of pediatric thyroid cancer) has a high rate of gene fusions which influence the histologic subtypes encountered in pediatric thyroid tumors, are associated with more extensive extrathyroidal disease, and offer unique options for targeted medical therapies. Differences are also seen in pediatric follicular thyroid cancer, although there are few studies of non-papillary pediatric thyroid tumors published in the literature due to their rarity, and in medullary carcinoma, which is most frequently diagnosed in the pediatric population in the setting of prophylactic thyroidectomies for known multiple endocrine neoplasia syndromes. The overall shift in the spectrum of histotypes and underlying molecular alterations common in pediatric thyroid cancer is important to recognize as it may directly influence diagnostic test selection and therapeutic recommendations.

Radiation-Induced Thyroid Cancers: Overview of Molecular Signatures

Enormous amounts of childhood thyroid cancers, mostly childhood papillary thyroid carcinomas (PTCs), after the Chernobyl nuclear power plant accident have revealed a mutual relationship between the radiation exposure and thyroid cancer development. While the internal exposure to radioactive ¹³¹I is involved in the childhood thyroid cancers after the Chernobyl accident, people exposed to the external radiation, such as atomic-bomb (A-bomb) survivors, and the patients who received radiation therapy, have also been epidemiologically demonstrated to develop thyroid cancers. In order to elucidate the mechanisms of radiation-induced carcinogenesis, studies have aimed at defining the molecular changes associated with the thyroid cancer development. Here, we overview the literatures towards the identification of oncogenic alterations, particularly gene rearrangements, and discuss the existence of radiation signatures associated with radiation-induced thyroid cancers.

AGK-BRAF is associated with distant metastasis and younger age in pediatric papillary thyroid carcinoma

BACKGROUND

The incidence of thyroid carcinoma has increased in most populations, including pediatric patients. The increase is almost exclusively due to an increase in the incidence of papillary thyroid carcinoma (PTC). Genetic alterations leading to mitogen-activated protein kinase (MAPK) pathway activation are highly prevalent in PTC, with BRAF V600E mutation being the most common event in adult PTC. Although a lower prevalence of BRAF V600E had been reported among pediatric patients, a higher prevalence of BRAF fusion has been identified in both radiation-exposed and sporadic pediatric PTC. However, little is known about the prognostic implications of BRAF fusions in pediatric PTC.

PROCEDURE

In this study, we investigated the prevalence of BRAF alterations (AGK-BRAF fusion and BRAF V600E mutation) in a large set of predominantly sporadic pediatric PTC cases and correlate with clinicopathological features. Somatic AGK-BRAF fusion was investigated by RT-PCR and confirmed by FISH break-apart. The BRAF V600E mutation was screened using Sanger sequencing.

RESULTS

AGK-BRAF fusion, found in 19% of pediatric PTC patients, was associated with distant metastasis and younger age. Conversely, the BRAF V600E, found in 15% of pediatric PTC patients, was correlated with older age and larger tumor size.

CONCLUSION

Collectively, our results advance knowledge concerning genetic bases of pediatric thyroid carcinoma, with potential implications for diagnosis, prognosis, and therapeutic approaches.

Gene Fusions in Thyroid Cancer

BACKGROUND

Gene fusions are known in many cancers as driver or passenger mutations. They play an important role in both the etiology and pathogenesis of cancer and are considered as potential diagnostic and prognostic markers and possible therapeutic targets. The spectrum and prevalence of gene fusions in thyroid cancer ranges from single cases up to 80%, depending on the specific type of cancer. During last three years, massive parallel sequencing technologies have revealed new fusions and allowed detailed characteristics of fusions in different types of thyroid cancer.

SUMMARY

This article reviews all known fusions and their prevalence in papillary, poorly differentiated and anaplastic, follicular, and medullary carcinomas. The mechanisms of fusion formation are described. In addition, the mechanisms of oncogenic transformation, such as altered gene expression, forced oligomerization, and subcellular localization, are given.

CONCLUSION

The prognostic value and perspectives of the utilization of gene fusions as therapeutic targets are discussed.

Molecular Testing for Oncogenic Gene Alterations in Pediatric Thyroid Lesions

BACKGROUND

Thyroid nodules are less common in pediatric patients (i.e., those ≤18 years) than they are in adults. The Bethesda System for Reporting Thyroid Cytopathology allows for individual risk stratification, but a significant number of nodules are indeterminate. Incorporating gene mutation panels and gene expression classifiers may aid in preoperative diagnosis. The overall aim of this study was to assess the prevalence of oncogene alterations in a representative pediatric population and across a broad-spectrum of thyroid tumor diagnoses.

METHODS

This was a retrospective cross-sectional evaluation of 115 archived samples, including: 47 benign (29 follicular adenoma, 11 diffuse hyperplasia, four thyroiditis, and three multinodular goiter), six follicular thyroid carcinomas (FTC), 24 follicular variant of papillary thyroid carcinomas (fvPTC), 27 classic variant of PTC (cPTC), eight diffuse sclerosing variant of PTC (dsvPTC), and three other PTC. Molecular testing was performed by multiplex qualitative polymerase chain reaction followed by bead array cytometry. Oncogene results were analyzed for association with age, sex, histology, lymph node metastasis, and intrathyroidal spread.

RESULTS

A mutation in one of the 17 molecular markers evaluated was found in: 2/6 (33%) FTC, 8/24 (33%) fvPTC, 17/27 (63%) cPTC, and 4/8 (50%) dsvPTC. Mutations in RAS or PAX8/PPARG were exclusive to FTC and fvPTC. BRAF was the most common mutation in cPTC (12/17; 71%), and RET/PTC was the only mutation associated with dsvPTC. Overall, a mutation was found in 32/68 (47%) malignant specimens, with a single follicular adenoma positive for PAX8/PPARG. The relative distribution of gene alterations in pediatric lesions was similar to adults. The presence of a BRAF mutation in pediatric cPTC did not predict a more invasive phenotype.

CONCLUSIONS

Of 33 nodules with genetic alterations, 32 were malignant. Mutations in RAS were most frequently associated with FTC, RET/PTC rearrangements with dsvPTC, and invasive fvPTC, and BRAF with cPTC. These results suggest a clinical role for mutational analysis of pediatric nodules to guide the surgical approach.

Diagnostic Limitation of Fine-Needle Aspiration (FNA) on Indeterminate Thyroid Nodules Can Be Partially Overcome by Preoperative Molecular Analysis: Assessment of RET/PTC1 Rearrangement in BRAF and RAS Wild-Type Routine Air-Dried FNA Specimens

Molecular markers are helpful diagnostic tools, particularly for cytologically indeterminate thyroid nodules. Preoperative RET/PTC1 rearrangement analysis in BRAF and RAS wild-type indeterminate thyroid nodules would permit the formulation of an unambiguous surgical plan. Cycle threshold values according to the cell count for detection of the RET/PTC1 rearrangement by real-time reverse transcription-polymerase chain reaction (RT-PCR) using fresh and routine air-dried TPC1 cells were evaluated. The correlation of RET/PTC1 rearrangement between fine-needle aspiration (FNA) and paired formalin-fixed paraffin-embedded (FFPE) specimens was analyzed. RET/PTC1 rearrangements of 76 resected BRAF and RAS wild-type classical PTCs were also analyzed. Results of RT-PCR and the Nanostring were compared. When 100 fresh and air-dried TPC1 cells were used, expression of RET/PTC1 rearrangement was detectable after 35 and 33 PCR cycles, respectively. The results of RET/PTC1 rearrangement in 10 FNA and paired FFPE papillary thyroid carcinoma (PTC) specimens showed complete correlation. Twenty-nine (38.2%) of 76 BRAF and RAS wild-type classical PTCs had RET/PTC1 rearrangement. Comparison of RET/PTC1 rearrangement analysis between RT-PCR and the Nanostring showed moderate agreement with a κ value of 0.56 (p = 0.002). The RET/PTC1 rearrangement analysis by RT-PCR using routine air-dried FNA specimen was confirmed to be technically applicable. A significant proportion (38.2%) of the BRAF and RAS wild-type PTCs harbored RET/PTC1 rearrangements.

Fusion Oncogenes Are the Main Genetic Events Found in Sporadic Papillary Thyroid Carcinomas from Children

BACKGROUND

Previous studies reported significant differences in the clinical presentation and outcomes of papillary thyroid carcinoma (PTC) in pediatric patients compared with adults. Previous studies have suggested that the clinicopathological differences observed between pediatric and adult PTCs may be due the existence of distinct genetic alterations. However, the knowledge of genetic events in pediatric PTCs is based primarily on studies in radiation-exposed PTCs or in the few studies that enrolled predominantly adolescent patients. The aim of this study was to characterize the known oncogenic alterations of the MAPK pathway found in adult and radiation-exposed PTCs in a cohort of predominantly sporadic pediatric PTC patients.

METHODS

Thirty-five pediatric PTCs were screened for the most prevalent fusions (RET/PTC1, RET/PTC2, RET/PTC3, ETV6-NTRK3, and AGK-BRAF) and point mutations (BRAFV600E and NRASQ61) described in sporadic pediatric PTCs. The mutational status was correlated with clinicopathological data.

RESULTS

Mutations were found in 20 out of 35 (57%) PTC cases. Fusion oncogenes were the main genetic alterations found. RET/PTC1-3 rearrangements were found in 13 (37%), ETV6-NTRK3 in 3 (9%), AGK-BRAF in 4 (11%), and BRAFV600E in 3 (9%). No mutation was found in NRASQ61. BRAFV600E was associated with older age and larger tumor size (p < 0.05), and RET/PTC3 was associated with a larger tumor size and multifocality (p < 0.05).

CONCLUSIONS

The genetic signature in this cohort was remarkably different than that observed in adults. Although observed at a lower prevalence, the spectrum of mutations was quite similar to that described in radiation-exposed pediatric PTCs. As mutations were unidentifiable in over 40% of the PTC cases, more comprehensive studies conducted in these patients will help to decipher the genetic landscape of sporadic pediatric PTCs.

AGK-BRAF gene fusion is a recurrent event in sporadic pediatric thyroid carcinoma

Thyroid cancer is the fastest increasing cancer worldwide in all age groups. Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer in both adults and children. PTC genomic landscape has been extensively studied in adults, but information regarding sporadic pediatric patients is lacking. Although BRAF V600E mutation is highly prevalent in adults, this mutation is uncommon in pediatric cases. As adult and pediatric PTC is a mitogen‐activated protein kinase‐driven cancer, this altered pathway might be activated by different genetic events. The aim of this study was to investigate the occurrence of AGK‐BRAF fusion gene, recently described in radiation‐exposed pediatric PTC, in a cohort of exclusively sporadic pediatric PTC. The series consisted of 30 pediatric PTC younger than 18 years of age at the time of diagnosis and 15 matched lymph node metastases (LNM). Primary tumors and matched LNM were screened for the presence of the AGK‐BRAF fusion transcript by RT‐PCR. To confirm the identity of the amplified products, randomly selected samples positive for the presence of the fusion transcripts were sequenced. Moreover, BRAF dual‐color, break‐apart probes confirmed BRAF rearrangement. Overall, the AGK‐BRAF fusion gene was detected in 10% (3/30) of primary tumors. For one of these cases, paired LNM was also available, which also shows the presence of AGK‐BRAF fusion gene. This study described, for the first time, the presence of AGK‐BRAF in sporadic pediatric PTC. Understanding the molecular events underlying pediatric PTC may improve preoperative diagnosis, allow molecular prognostication and define a therapeutic approach toward sporadic PTC patients.

Mutational Analysis in Pediatric Thyroid Cancer and Correlations with Age, Ethnicity, and Clinical Presentation

BACKGROUND

Well-differentiated thyroid cancer (WDTC) incidence in pediatrics is rising, most being papillary thyroid carcinoma (PTC). The objective of the study was to assess the prevalence of different mutations in pediatric WDTC and correlate the genotype with the clinical phenotype.

METHODS

This is a single-center retrospective study. Thyroid tissue blocks from 42 consecutive pediatric WDTC patients who underwent thyroidectomy between 2001 and 2013 were analyzed at Quest Diagnostics for BRAF(V600E), RAS mutations (N,K,H), and RET/PTC and PAX8/PPARγ rearrangements, using validated molecular methods. Thyroid carcinomas included PTC, follicular thyroid carcinoma (FTC), and follicular variant of PTC (FVPTC).

RESULTS

Thirty-nine samples (29 females) were genotyped. The mean age at diagnosis was 14.7 years (range 7.9-18.4 years), and most were Hispanic (56.4%) or Caucasian (35.9%). The mean follow-up period was 2.9 years. Mutations were noted in 21/39 (53.8%), with both BRAF(V600E) (n = 9), and RET/PTC (n = 6) detected only in PTC. Mutations were detected in 2/5 FTC (PAX8/PPARγ and NRAS) and 3/6 FVPTC cases (PAX8/PPARγ). Of 28 PTC patients, 57.1% had mutations: 32.1% with BRAF(V600E), 21.4% with RET/PTC, and 3.6% with NRAS. Of patients with BRAF(V600E), 77.8% were Hispanic and 88.9% were >15 years, while all RET/PTC-positive patients were ≤15 years (p = 0.003). Tumor size, lymph node involvement, and distant metastasis at diagnosis (or soon after (131)I ablation) did not vary significantly based on the mutation.

CONCLUSIONS

BRAF(V600E) was the most common mutation, especially in older and Hispanic adolescents. A larger, ethnically diverse pediatric cohort followed long term will enable the genotypic variability, clinical presentation, and response to therapy to be better assessed.

Are we really at the dawn of understanding sporadic pediatric thyroid carcinoma?

Data from the National Cancer Institute and from the literature have disclosed an increasing incidence of thyroid cancer in children, adolescents and adults. Although children and adolescents with thyroid cancer tend to present with more advanced disease than adults, their overall survival rate is excellent; however, there is no clear explanation for the differences observed in the clinicopathological outcomes in these age groups. There has been an ongoing debate regarding whether the clinicopathological differences may be due to the existence of distinct genetic alterations. Efforts have been made to identify these acquired genetic abnormalities that will determine the tumor's biological behavior and ultimately allow molecular prognostication. However, most of the studies have been performed in radiation-exposed pediatric thyroid carcinoma. Therefore, our understanding of the role of these driver mutations in sporadic pediatric differentiated thyroid cancer development is far from complete, and additionally, there is a strong need for studies in both children and adolescents. The aim of this review is to present an extensive literature review with emphasis on the molecular differences between pediatric sporadic and radiation-exposed differentiated thyroid carcinomas and adult population.

BRAF V600E and decreased NIS and TPO expression are associated with aggressiveness of a subgroup of papillary thyroid microcarcinoma

BACKGROUND

Thyroid cancer incidence has dramatically increased worldwide over the last two decades. The rise is mostly due to an increased detection of small papillary thyroid carcinomas (PTCs) (≤20  mm), predominantly microPTC (≤10  mm). Although small tumors generally have an excellent outcome, a considerable percentage may have a more aggressive disease and worse prognosis. The clinical challenge is to preoperatively identify those tumors that are more likely to recur.

AIM

To improve risk stratification and patient management, we sought to determine the prognostic value of BRAF V600E, NRAS or RET/PTC mutations in patients with PTC measuring <20  mm, mainly microPTC.

METHODS

The prevalence of RET/PTC fusion genes was examined by quantitative RT-PCR. BRAF V600E and NRAS Q61 mutations were determined by PCR sequencing. To further elucidate why some small PTC are less responsive to radioactive iodine treatment therapy, we explored if these genetic alterations may modulate the expression of iodine metabolism genes (NIS, TPO, TG, TSHR and PDS) and correlated with clinico-pathological findings that are predictors of recurrence.

RESULTS

This study shows that tumors measuring ≤20  mm exhibited higher prevalence of BRAF V600E mutation, which correlated with aggressive histopathological parameters, higher risk of recurrence, and lower expression of NIS and TPO. Although this correlation was not found when microPTC were evaluated, we show that tumors measuring 7-10  mm, which were positive for BRAF mutation, presented more aggressive features and lower expression of NIS and TPO.

CONCLUSION

We believe that our findings will help to decide the realistic usefulness of BRAF V600E mutation as a preoperative marker of poor prognosis in small PTC, primarily in microPTC.

Management Guidelines for Children with Thyroid Nodules and Differentiated Thyroid Cancer

BACKGROUND

Previous guidelines for the management of thyroid nodules and cancers were geared toward adults. Compared with thyroid neoplasms in adults, however, those in the pediatric population exhibit differences in pathophysiology, clinical presentation, and long-term outcomes. Furthermore, therapy that may be recommended for an adult may not be appropriate for a child who is at low risk for death but at higher risk for long-term harm from overly aggressive treatment. For these reasons, unique guidelines for children and adolescents with thyroid tumors are needed.

METHODS

A task force commissioned by the American Thyroid Association (ATA) developed a series of clinically relevant questions pertaining to the management of children with thyroid nodules and differentiated thyroid cancer (DTC). Using an extensive literature search, primarily focused on studies that included subjects ≤18 years of age, the task force identified and reviewed relevant articles through April 2014. Recommendations were made based upon scientific evidence and expert opinion and were graded using a modified schema from the United States Preventive Services Task Force.

RESULTS

These inaugural guidelines provide recommendations for the evaluation and management of thyroid nodules in children and adolescents, including the role and interpretation of ultrasound, fine-needle aspiration cytology, and the management of benign nodules. Recommendations for the evaluation, treatment, and follow-up of children and adolescents with DTC are outlined and include preoperative staging, surgical management, postoperative staging, the role of radioactive iodine therapy, and goals for thyrotropin suppression. Management algorithms are proposed and separate recommendations for papillary and follicular thyroid cancers are provided.

CONCLUSIONS

In response to our charge as an independent task force appointed by the ATA, we developed recommendations based on scientific evidence and expert opinion for the management of thyroid nodules and DTC in children and adolescents. In our opinion, these represent the current optimal care for children and adolescents with these conditions.

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.

Radiation signatures in childhood thyroid cancers after the Chernobyl accident: possible roles of radiation in carcinogenesis

After the Tokyo Electric Power Company Fukushima Daiichi nuclear power plant accident, cancer risk from low-dose radiation exposure has been deeply concerning. The linear no-threshold model is applied for the purpose of radiation protection, but it is a model based on the concept that ionizing radiation induces stochastic oncogenic alterations in the target cells. As the elucidation of the mechanism of radiation-induced carcinogenesis is indispensable to justify the concept, studies aimed at the determination of molecular changes associated with thyroid cancers among children who suffered effects from the Chernobyl nuclear accident will be overviewed. We intend to discuss whether any radiation signatures are associated with radiation-induced childhood thyroid cancers.

Oncogenic rearrangements driving ionizing radiation-associated human cancer

The Chernobyl nuclear disaster has caused a remarkable increase in radiation-induced papillary thyroid carcinoma in children and young adults. In this issue of the JCI, Ricarte-Filho and colleagues demonstrate that chromosomal rearrangements are the oncogenic "drivers" in most post-Chernobyl carcinomas and that they often lead to unscheduled activation of the MAPK signaling pathway. These findings represent a major step forward in our understanding of radiation-induced carcinogenesis and suggest various hypotheses about the mechanisms underlying the formation and selection of gene rearrangements during cancer cell evolution.

Papillary thyroid cancer and inflammatory bowel disease: Is there a relationship?

AIM: To formally study age of diagnosis of papillary thyroid cancer (PTC) in inflammatory bowel disease (IBD) patients and evaluate the prevalence of PTC in IBD patients compared to a control population.

METHODS: We were interested in testing the hypothesis that patients with IBD are more likely to be diagnosed with PTC than a control population. A retrospective cohort analysis was performed using the University of Pennsylvania Health System’s electronic database. Outpatients from 1998-2009 were included in the search, and patients in the cohort were selected based on ICD-9 codes. Inclusion criteria included the diagnosis of Crohn’s disease (CD) or ulcerative colitis (UC) and the concurrent diagnosis of thyroid cancer in comparison to a control population. Using these methods 912 patients with CD and 1774 with UC were compared to 1638 diverticulitis and 19 447 asthma controls. Statistics were performed using corrected chi-square analysis. The primary outcome for this study was the diagnosis of PTC. Approval to conduct this study was obtained by the Institutional Review Board at the University of Pennsylvania.

RESULTS: The mean age was 47.5 years (range: 18-102 years) and 66% patients were female. An analysis of variance model was used to compare the age of PTC diagnosis between the CD, UC, asthma and diverticulitis groups, and a statistically significant difference in age at PTC diagnosis was noted across all groups (F = 6.35, df = 3, P = 0.0006). The age of PTC diagnosis in CD patients was statistically significantly lower than UC, asthma, and diverticulitis patients (average PTC diagnosis age for CD 25, UC 49, asthma 45, diverticulitis 63). After covarying for sex and age in 2009, the difference in age at PTC diagnosis remained statistically significant (F = 4.13, df = 3, P = 0.0089). A total of 86 patients were diagnosed with PTC. Nine patients (0.5%) with UC were diagnosed with PTC. Patients with UC were not shown to be more likely to develop PTC [odds ratio (OR): 1.544, 95%CI 0.767-3.108] compared to asthma controls. Four patients (0.4%) with CD were diagnosed with PTC. Patients with CD were not shown to be more likely to develop PTC (OR: 1.334, 95%CI 0.485-3.672) compared to a control population with asthma. Nine patients (0.5%) with a history of diverticulitis were diagnosed with PTC. Patients with diverticulitis were not shown to be more likely to develop PTC (OR: 1.673, 95%CI 0.831-3.368) compared to asthma controls. Patients with CD or UC were not less likely to develop PTC compared to those with diverticulitis (CD OR: 0.80, 95%CI 0.25-2.60; UC OR: 0.92, 95%CI 0.37-2.33). None of the patients used immunosuppressant medications prior to the diagnosis of PTC (azathioprine, 6-mercaptopurine, and methotrexate).

CONCLUSION: There is a significant difference in age of diagnosis of PTC in patients with CD compared to patients with UC and the control populations studied.

Use of molecular biomarkers in FNA specimens to personalize treatment for thyroid surgery

BACKGROUND

Accurate preoperative assessment of thyroid nodules with fine-needle aspiration biopsy (FNAB) continues to be a challenge, often resulting in unnecessary diagnostic surgical intervention. The detection of several novel gene mutations in differentiated thyroid cancer (DTC) over the last decade has led to the diagnostic use of these oncogenic alterations to improve FNAB sensitivity and specificity.

METHODS AND RESULTS

Thyroid oncogene mutations including BRAF, RAS, and RET/PTC are reviewed. The potential benefit of using this panel on fine-needle aspiration (FNA) cytology samples will be described.

CONCLUSION

Our use of ''reflexive'' molecular testing demonstrates its clinical value in conjunction with FNAB cytology, representing an application of personalized molecular medicine to guide appropriate surgical therapy.

The role of fragile sites in sporadic papillary thyroid carcinoma

The incidence of thyroid cancer is increasing, especially papillary thyroid carcinoma (PTC), making it currently the fastest-growing cancer among women. Reasons for this increase remain unclear, but several risk factors including radiation exposure and improved detection techniques have been suggested. Recently, the induction of chromosomal fragile site breakage was found to result in the formation of RET/PTC1 rearrangements, a common cause of PTC. Chromosomal fragile sites are regions of the genome with a high susceptibility to forming DNA breaks and are often associated with cancer. Exposure to a variety of external agents can induce fragile site breakage, which may account for some of the observed increase in PTC. This paper discusses the role of fragile site breakage in PTC development, external fragile site-inducing agents that may be potential risk factors for PTC, and how these factors are especially targeting women.

RET TKI: potential role in thyroid cancers

The increasing incidence of thyroid cancer is associated with a higher number of advanced disease characterized by the loss of cancer differentiation and metastatic spread. The knowledge of the molecular pathways involved in the pathogenesis of thyroid cancer has made possible the development of new therapeutic drugs able to blockade the oncogenic kinases (RET/PTC) or signaling kinases (vascular endothelial growth factor receptor [VEGFR]) involved in cellular growth and proliferation. Some clinical trials have been conducted showing the ability of targeted therapies able to inhibit RET(sorafenib, imatinib, vandetanib) in stabilizing the course of the disease. The aim of the introduction of these targeted therapies is to extend life duration assuring a good quality of life; however, further studies are needed to reach these goals.

Pediatric thyroid cancer

Thyroid cancer is an uncommon childhood malignancy that presents primarily in young children or adolescent females and may be related to radiation exposure or genetic predisposition. Gene alterations, such as RET mutation or RET/PTC rearrangement, are not uncommon. Recent studies have lead to an increased understanding of the role of these particular gene alterations in the diagnosis, prognosis, and treatment of thyroid cancer. Surgery remains the mainstay of treatment for thyroid cancer followed by radioactive iodine when appropriate. In patients with MEN2, prophylactic thyroidectomy is recommended, although a delay in the initial diagnosis is common. With early aggressive treatment and long-term follow-up, these patients generally have excellent outcomes. Recent research suggests potential usefulness of novel therapies directed at oncogenic signaling pathways, modulators of growth, angiogenesis inhibitors, immunomodulators, and gene therapy.

Oncogenic alterations in papillary thyroid cancers of young patients

BACKGROUND

Papillary thyroid carcinoma (PTC) in young people usually has an aggressive initial presentation, though a good general prognosis despite recurrences in 10%-20% of patients. A number of genetic alterations that activate the mitogen-activated protein kinase (MAPK) pathway have been found in PTC. Some of these alterations have been identified as prognostic factors of PTC in adults. The objective of the current study was to comprehensively characterize all known oncogenic alterations of the MAPK pathway in young people.

METHODS

One hundred three PTCs removed from 9 children, 19 adolescents, and 75 young adults were submitted to molecular analyses.

RESULTS

Altogether, 57 alterations were found in 56 PTCs (55%) corresponding to V600E BRAF in 20.3%, RAS mutations in 12.6%, RET/PTC 1 in 11.6%, RET/PTC 3 in 8.7%, and rearrangement of NTRK in 1.9%. The prevalence of all alterations increased with age (22.2% in children; 52.6% in adolescents, 51.4% in adults 20-25 years, and 55.1% in adults 25-35 years). Prevalence increased from 39.2% earlier to 61.3% after 20 years mainly due to BRAF mutations. Classic-type PTC was associated with a larger prevalence of alterations, predominantly BRAF and RET/PTC, whereas the follicular variant was chiefly associated with RAS. RET/PTC (1 and 3) was significantly associated with extrathyroid extension (ET) and lymph node metastasis (es) (LNM). This association was found in the adult group. There were no associations of BRAF or RAS mutations with ET or LNM. A 3-year median follow up was available for 90 patients. RET/PTC 1 and 3 was associated with short-term disease dissemination (cervical lymph node recurrences and distant metastases) in young adults (p=0.001). Persistent illness was more prevalent in patients with (15%) than in patients without (7%) genetic alterations.

CONCLUSION

PTCs in young patients display a low prevalence of the already identified oncogenic alterations. The increasing prevalence with age is mainly due to V600E BRAF mutation. There is no relation between tumor aggressiveness and BRAF mutation. There is a relation between the presence of RET/PTC (1 and 3) and the histological and clinical short-term aggressiveness of PTC in the population of young adults. Such a relation is not found in children and adolescents.

Prognosis and prognostic factors of papillary thyroid carcinoma in patients under 20 years

Age is an important prognostic factor of papillary thyroid carcinoma (PTC). In this study, we investigated the prognosis and prognostic factors of PTC in patients younger than 20 years. We enrolled 110 patients who underwent initial surgery at Kuma Hospital between 1987 and 2008. Tumor size > 4 cm, metastatic node ≥ 3 cm, and significant extrathyroid extension were more frequently detected in 8 patients with distant metastasis at diagnosis than in 102 patients without distant metastasis. Ten- and 20-year lymph node recurrence-free survival (LN-RFS) and distant recurrence-free survival (DRFS) rates were 84 and 80%, and 95 and 89%, respectively. Metastatic node ≥ 3 cm, age ≤ 16 years, tumor size > 4 cm, and male gender affected LN-RFS, and the former two had an independent prognostic value in multivariate analysis. Metastastic node ≥ 3 cm, significant extrathyroid extension, age ≤ 16 years, tumor size > 4 cm, and a male gender predicted a poor DRFS, and the former two were independent prognostic factors. To date, only 2 patients have died of PTC. These findings suggest that, in the subset of PTC patients younger than 20 years, metastatic node ≥ 3 cm, significant extension, and age ≤ 16 were important signs of aggressiveness of carcinoma, and careful treatment is necessary for patients with these characteristics, although the cause-specific survival was excellent.

RET/PTC rearrangement in benign and malignant thyroid diseases: a clinical standpoint

Cytological examination of fine needle aspiration biopsy is the primary means for distinguishing benign from malignant nodules. However, as inconclusive cytology is very frequent, the introduction of molecular markers in the preoperative diagnosis of thyroid nodules has been proposed in recent years. In this article, we review the clinical implications of preoperative detection of rearrangements of the RET gene (RET/papillary thyroid carcinoma (PTC)) in thyroid nodules. The prevalence of RET/PTC in PTC depends on the histological subtypes, geographical factors, radiation exposure, and detection method. Initially, RET/PTC was considered an exclusive PTC hallmark and later it was also found sporadically in benign thyroid lesions. More recently, the very sensitive detection methods, interphase fluorescence in situ hybridization (FISH) and Southern blot on RT-PCR amplicons, demonstrated that the oligoclonal occurrence of RET rearrangement in benign thyroid lesions is not a rare event and suggested that it could be associated with a faster enlargement in benign nodules. For this reason, RET/PTC cannot be considered as an absolute marker of PTC, and its diagnostic application must be limited to assays able to distinguish between clonal and oligoclonal expression. Detection of RET/PTC by quantitative assays will be useful for diagnostic purposes in cytology specimens when a precise cutoff will be fixed in a clinical setting. Until that time, less sensitive RET/PTC detection methods and FISH analysis remain the most appropriate means to refine inconclusive cytology. Future studies with a long follow-up will further clarify the clinical significance of low level of RET rearrangements in benign nodules.

Molecular analysis of thyroid tumors

Thyroid cancer is the most common endocrine malignancy, and its incidence is rising in the USA and other countries. Papillary and follicular thyroid carcinomas are the two most common types of thyroid cancer. Non-overlapping genetic alterations, including BRAF and RAS point mutations, and RET/PTC and PAX8/PPARγ rearrangements, are found in more than 70% of papillary and follicular thyroid carcinomas. These represent the most common genetic alterations in thyroid cancer, as well as molecular markers of diagnostic and prognostic significance. The use of these and other emerging molecular markers will likely improve the diagnosis of malignancy in thyroid nodules as well as facilitate more individualized operative and postoperative management. Herein, we provide a brief overview of the common genetic alterations in papillary and follicular thyroid carcinoma and discuss the diagnostic and prognostic significance thereof.

Targeted treatment of differentiated and medullary thyroid cancer

The incidence of thyroid cancer is increasing, with a concomitant increase in the number of patients with advanced and metastatic disease. Discoveries regarding the pathogenesis of thyroid cancer have led to the recent development of new therapeutic agents that are beginning to appear on the market. Many of these new agents are targeted kinase inhibitors primarily affecting oncogenic kinases (BRAF V600E, RET/PTC) or signaling kinases (VEGFR, PDGFR). Some of these agents report significant partial response rates, while others attain stabilization of disease as their best response. Their impact on survival is unclear. While these agents target similar pathways, a wide variety of differences exist regarding efficacy and side effect profile. Current expert opinion advises that these agents be used only in a specific subset of patients.

Mechanisms of chromosomal rearrangements in solid tumors: the model of papillary thyroid carcinoma

Thyroid cancer, and its most common type, papillary carcinoma, frequently have chromosomal rearrangements and therefore represent a good model for the understanding of mechanisms of chromosomal rearrangements in solid tumors. Several types of rearrangement known to occur in thyroid cancer, including RET/PTC, NTRK1 and BRAF/AKAP9, are more common in radiation-associated thyroid tumors and RET/PTC can be induced experimentally by exposing human thyroid cells to ionizing radiation. In this review, the molecular mechanisms of generation of RET/PTC and other chromosomal rearrangements are discussed, with the emphasis on the role of nuclear architecture and interphase gene proximity in the generation of intrachromosomal rearrangements in thyroid cells.

Thyroid cancer: current molecular perspectives

The thyroid cancer is a rare oncological entity, representing no more than 1% of all human malignant neoplasms. Recently, it has been demonstrated a sharp increase in incidence of differentiated thyroid carcinoma, equally occurring in both sexes. So far, multiple genetic alterations have been identified in differentiated thyroid carcinoma, leading to investigate the clinical utility of genetic studies. In particular, molecular genetic approaches searching for gene mutations in the material collected by fine needle ago-biopsy may have a particular utility in small nodules and in those specimens with an indeterminate cytology. The expansion of knowledge about genetic mutations occurring in different thyroid tumors has characterized recent years, allowing the identification of a correlation between specific mutations and phenotypic characteristics of thyroid cancers, essential for their prognosis. This review will briefly report on the histological features and the new entity represented by thyroid microcarcinoma and will focus on both environmental and genetic aspects associated with the occurrence of thyroid cancer.

Molecular diagnostics and predictors in thyroid cancer

BACKGROUND

The accuracy of cancer detection in thyroid nodules by fine-needle aspiration (FNA) cytology and prognostication of thyroid cancer needs further improvement and can benefit from testing for molecular alterations known to occur in thyroid tumors.

SUMMARY

Recent studies have demonstrated the feasibility of mutation detection in clinical FNA samples from thyroid nodules and their contribution to improving the diagnostic accuracy of FNA cytology. It appears that molecular testing is most beneficial for thyroid FNA samples with indeterminate cytology, where it can resolve the diagnosis in a significant number of cases. In addition to BRAF mutation, which has been studied most extensively, detection of RAS, RET/PTC, and PAX8/PPARgamma mutations also contribute substantially to cancer diagnosis. Some of these molecular markers, particularly BRAF, can also be used for tumor prognostication. In clinical setting, molecular testing of thyroid FNA samples and surgically removed tumors should utilize a restricted number of techniques that provide high accuracy and specificity of mutation detection.

CONCLUSION

Testing for cancer-specific mutations in thyroid FNA samples and surgically removed tumor tissues increases diagnostic accuracy of FNA cytology and offers better prognostication of thyroid cancer.

Molecular rearrangements in papillary thyroid carcinomas

Papillary thyroid cancer is unusual among epithelial malignancies in that it is associated with a number of chromosomal rearrangements. The most common of these is the Ret oncogene, normally silent in the follicular cell, but which has been shown to be rearranged to the promoter region of a variety of different genes, all of which are constituently expressed in the thyroid follicular cell. It has been suggested that chromosomes in the thyroid cell are arranged within the nucleus in such a way as to predispose the cell to inappropriate fusion in the advent of DNA double-strand breakage. The presence of tumour specific fusion genes, and their transcribed proteins, presents a possible therapeutic target for thyroid cancer, but the relative contribution of the gene rearrangement in the growth and development of the tumour will need careful evaluation before clinical studies could take place.

Diffuse sclerosing variant is a major subtype of papillary thyroid carcinoma in the young

BACKGROUND

Pediatric thyroid cancer differs from adult thyroid cancer in presentation and outcome. Pediatric thyroid cancer has a higher recurrence rate and greater percentage of lymph node and pulmonary metastasis. The clinicopathologic characteristics of pediatric thyroid cancer according to the histologic subtype have not been reported, however. In this study, we determined the histological subtypes of pediatric thyroid cancer and analyzed other clinicopathologic characteristics.

METHODS

All patients with thyroid cancer who were admitted to Severance Hospital, Seoul, South Korea, were retrospectively reviewed; their age was <20 years at diagnosis, and they were seen between January 1995 and August 2008.

RESULTS

Sixty-eight patients were identified. The histologic types of thyroid carcinoma were papillary thyroid carcinoma (PTC) in 57 (83.8%), follicular carcinoma in 8 (11.8%), and poorly differentiated carcinoma in 3 (4.4%). There were 28 (41.2%) cases of diffuse sclerosing variant of papillary carcinoma (DSVPC), 26 (38.2%) of conventional PTC, 2 (2.9%) of follicular PTC, and 1 (1.5%) cribriform-morular PTC. In patients with PTC, there was a higher incidence of bilateral thyroid involvement (p = 0.003), extrathyroidal extension (p = 0.009), and lymph node involvement (p = 0.018), and lower recurrence-free survival (p = 0.032) in DSVPC than in non-DSVPC. Univariate regression analysis revealed that extrathyroidal extension (p = 0.025) and tumor size (p = 0.001) were positively associated with a shorter time to recurrence.

CONCLUSION

DSVPC is a major subtype of PTC in the young.

High rate of BRAF and RET/PTC dual mutations associated with recurrent papillary thyroid carcinoma

PURPOSE

Papillary thyroid carcinoma (PTC), the most common thyroid malignancy, usually possesses BRAF mutation or rearranged in translation (RET)/PTC rearrangements. PTC usually possesses BRAF mutation or RET/PTC rearrangements. The mutation status of patients with recurrent PTC has never been characterized in a large population.

EXPERIMENTAL DESIGN

Mutation status was determined in a cohort of 54 patients with recurrent PTC and analyzed for clinicopathologic relationships. BRAF and ras mutations were determined by PCR and sequencing of genomic DNA. RET/PTC rearrangements were analyzed by reverse transcription-PCR.

RESULTS

BRAF mutation in exon 15 (V600E) was found in 42/54 (77.8%) recurrent PTC patients. The RET/PTC rearrangements were detected in 9 of 54 (16.7%) patients. In addition, 5 of 54 (9.3%) recurrent PTC patients had both a BRAF mutation and a RET/PTC rearrangement. The prevalence of tumors with dual mutations found in the recurrent population far exceeds the frequency historically reported for patients with primary PTC. Patients with dual mutations were significantly older (80% older than 45 years) than patients with a BRAF mutation alone (38% older than 45 years).

CONCLUSIONS

Recurrent PTC is significantly associated with a predominant BRAF mutation. RET/PTC rearrangements, although commonly associated with primary PTCs in younger patients, are uncommonly found in recurrent PTC patients. In addition, the incidence of dual mutations was higher in patients with recurrent PTC than in those primary PTC, as reported by others.

Transcript level modulates the inherent oncogenicity of RET/PTC oncoproteins

Mutations to the RET proto-oncogene occur in as many as one in three cases of thyroid cancer and have been detected in both the medullary (MTC) and the papillary (PTC) forms of the disease. Of the nearly 400 chromosomal rearrangements resulting in oncogenic fusion proteins that have been identified to date, the rearrangements that give rise to RET fusion oncogenes in PTC remain the paradigm for chimeric oncoprotein involvement in solid tumors. RET-associated PTC tumors are phenotypically indolent and relatively less aggressive than RET-related MTCs. The mechanism(s) contributing to the differences in oncogenicity of RET-related MTC and PTC remains unexplained. Here, through cellular and molecular characterization of the two most common RET/PTC rearrangements (PTC1 and PTC3), we show that RET/PTC oncoproteins are highly oncogenic when overexpressed, with the ability to increase cell proliferation and transformation. Further, RET/PTCs activate similar downstream signaling cascades to wild-type RET, although at different levels, and are relatively more stable as they avoid lysosomal degradation. Absolute quantitation of transcript levels of RET, CCDC6, and NCOA4 (the 5' fusion genes involved in PTC1 and PTC3, respectively) suggest that these rearrangements result in lower RET expression in PTCs relative to MTCs. Together, our findings suggest PTC1 and PTC3 are highly oncogenic proteins when overexpressed, but result in indolent disease compared with RET-related MTCs due to their relatively low expression from the NCOA4 and CCDC6 promoters in vivo.

ret/PTC activation is not associated with individual radiation dose estimates in a pilot study of neoplastic thyroid nodules arising in Russian children and adults exposed to Chernobyl fallout

BACKGROUND

Ionizing radiation is the strongest risk factor known for the development of thyroid neoplasia. While previous studies have demonstrated a high prevalence of ret/papillary thyroid cancer (PTC) activation in cohorts of patients developing thyroid nodules after childhood exposure to ionizing radiation, no study has directly compared ret/PTC activation with individual estimates of radiation dose to the thyroid. This study combines individual thyroid dosimetry data with molecular analysis of surgically removed thyroid nodules in order to determine if ret/PTC activation in thyroid nodules is associated with increasing estimated radiation dose from Chernobyl.

METHODS

This pilot study included adults and children diagnosed with PTC (n = 76) and children diagnosed with follicular adenomas (n = 24) during May 1986 through December 1999, who were living in the Bryansk Oblast of the Russian Federation at the time of the Chernobyl accident, who had paraffin-embedded thyroid surgical samples available and for whom an individual dose to the thyroid could be estimated. The frequency of ret/PTC activation was determined using RT-PCR analysis. Individual radiation doses to the thyroid were estimated using a semiempirical model, and data were collected by detailed interview, primarily of the participant's mother.

RESULTS

ret/PTC oncogene activation was detected in 23.8% (5/21) and 14.5% (8/55) of the childhood and adult PTC cases, respectively, and 8.3% (2/24) of the follicular adenoma cases. No statistically significant differences were noted in age at the time of exposure or diagnosis, gender, latency period, or estimated radiation dose between PTC patients with or without ret/PTC activation. Further, no significant dose-response relationship was detected among PTC patients with ret/PTC activation.

CONCLUSIONS

Factors other than individual thyroid radiation doses may influence the development and subsequent detection of ret/PTC oncogene activation in radiation related PTC arising in the Bryansk Oblast of the Russian Federation in the aftermath of the Chernobyl accident.

Pathology and cytologic features of thyroid neoplasms

Most thyroid neoplasms arise from follicular cells and are well differentiated. Anaplastic and poorly differentiated carcinomas are rare and have a high mortality. Five percent of tumors are of C-cell origin, and 20% to 25% of these are hereditary. Thyroid lymphoma is rare and occurs in the setting of Hashimoto's thyroiditis. Fine needle aspiration biopsy is the best diagnostic tool to classify thyroid neoplasms.