Molecular Genetics of Thyroid Cancer in Children and Adolescents

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.

Thyroid Cancer: A Review

Importance

Approximately 43 720 new cases of thyroid carcinoma are expected to be diagnosed in 2023 in the US. Five-year relative survival is approximately 98.5%. This review summarizes current evidence regarding pathophysiology, diagnosis, and management of early-stage and advanced thyroid cancer.

Observations

Papillary thyroid cancer accounts for approximately 84% of all thyroid cancers. Papillary, follicular (≈4%), and oncocytic (≈2%) forms arise from thyroid follicular cells and are termed well-differentiated thyroid cancer. Aggressive forms of follicular cell-derived thyroid cancer are poorly differentiated thyroid cancer (≈5%) and anaplastic thyroid cancer (≈1%). Medullary thyroid cancer (≈4%) arises from parafollicular C cells. Most cases of well-differentiated thyroid cancer are asymptomatic and detected during physical examination or incidentally found on diagnostic imaging studies. For microcarcinomas (≤1 cm), observation without surgical resection can be considered. For tumors larger than 1 cm with or without lymph node metastases, surgery with or without radioactive iodine is curative in most cases. Surgical resection is the preferred approach for patients with recurrent locoregional disease. For metastatic disease, surgical resection or stereotactic body irradiation is favored over systemic therapy (eg, lenvatinib, dabrafenib). Antiangiogenic multikinase inhibitors (eg, sorafenib, lenvatinib, cabozantinib) are approved for thyroid cancer that does not respond to radioactive iodine, with response rates 12% to 65%. Targeted therapies such as dabrafenib and selpercatinib are directed to genetic mutations (BRAF, RET, NTRK, MEK) that give rise to thyroid cancer and are used in patients with advanced thyroid carcinoma.

Conclusions

Approximately 44 000 new cases of thyroid cancer are diagnosed each year in the US, with a 5-year relative survival of 98.5%. Surgery is curative in most cases of well-differentiated thyroid cancer. Radioactive iodine treatment after surgery improves overall survival in patients at high risk of recurrence. Antiangiogenic multikinase inhibitors and targeted therapies to genetic mutations that give rise to thyroid cancer are increasingly used in the treatment of metastatic disease.

Genetic alterations landscape in paediatric thyroid tumours and/or differentiated thyroid cancer: Systematic review

Differentiated thyroid cancer (DTC) is a rare disease in the paediatric population (≤ 18 years old. at diagnosis). Increasing incidence is reflected by increases in incidence for papillary thyroid carcinoma (PTC) subtypes. Compared to those of adults, despite aggressive presentation, paediatric DTC has an excellent prognosis. As for adult DTC, European and American guidelines recommend individualised management, based on the differences in clinical presentation and genetic findings. Therefore, we conducted a systematic review to identify the epidemiological landscape of all genetic alterations so far investigated in paediatric populations at diagnosis affected by thyroid tumours and/or DTC that have improved and/or informed preventive and/or curative diagnostic and prognostic clinical conduct globally. Fusions involving the gene RET followed by NTRK, ALK and BRAF, were the most prevalent rearrangements found in paediatric PTC. BRAF V600E was found at lower prevalence in paediatric (especially ≤ 10 years old) than in adults PTC. We identified TERT and RAS mutations at very low prevalence in most countries. DICER1 SNVs, while found at higher prevalence in few countries, they were found in both benign and DTC. Although the precise role of DICER1 is not fully understood, it has been hypothesised that additional genetic alterations, similar to that observed for RAS gene, might be required for the malignant transformation of these nodules. Regarding aggressiveness, fusion oncogenes may have a higher growth impact compared with BRAF V600E. We reported the shortcomings of the systematized research and outlined three key recommendations for global authors to improve and inform precision health approaches, glocally.

Fusion Oncogenes in Patients With Locally Advanced or Distant Metastatic Differentiated Thyroid Cancer

CONTEXT

Fusion oncogenes are involved in the underlying pathology of advanced differentiated thyroid cancer (DTC), and even the cause of radioactive iodine (RAI)-refractoriness.

OBJECTIVE

We aimed to investigation between fusion oncogenes and clinicopathological characteristics involving a large-scale cohort of patients with advanced DTC.

METHODS

We collected 278 tumor samples from patients with locally advanced (N1b or T4) or distant metastatic DTC. Targeted next-generation sequencing with a 26-gene ThyroLead panel was performed on these samples.

RESULTS

Fusion oncogenes accounted for 29.86% of the samples (72 rearrangement during transfection (RET) fusions, 7 neurotrophic tropomyosin receptor kinase (NTRK) fusions, 4 anaplastic lymphoma kinase (ALK) fusions) and occurred more frequently in pediatric patients than in their adult counterparts (P = .003, OR 2.411, 95% CI 1.329-4.311) in our cohort. DTCs with fusion oncogenes appeared to have a more advanced American Joint Committee on Cancer (AJCC)_N and AJCC_M stage (P = .0002, OR 15.47, 95% CI 2.54-160.9, and P = .016, OR 2.35, 95% CI 1.18-4.81) than those without. DTCs with fusion oncogenes were associated with pediatric radioactive iodine (RAI) refractoriness compared with those without fusion oncogenes (P = .017, OR 4.85, 95% CI 1.29-15.19). However, in adult DTCs, those with fusion oncogenes were less likely to be associated with RAI refractoriness than those without (P = .029, OR 0.50, 95% CI 0.27-0.95), owing to a high occurrence of the TERT mutation, which was the most prominent genetic risk factor for RAI refractoriness in multivariate logistic regression analysis (P < .001, OR 7.36, 95% CI 3.14-17.27).

CONCLUSION

Fusion oncogenes were more prevalent in pediatric DTCs than in their adult counterparts and were associated with pediatric RAI refractoriness, while in adult DTCs, TERT mutation was the dominant genetic contributor to RAI refractoriness rather than fusion oncogenes.

Single BRAFV600E mutation is not associated with aggressive biological behavior in adolescent and pediatric papillary thyroid carcinoma

BACKGROUND

Papillary thyroid carcinoma is more likely to show aggressive biological behaviors in the majority of pediatric patients than in adult patients. The aim of this study was to investigate the mutation rate of the BRAFV600E gene in adolescents and children with papillary thyroid carcinoma and to analyze the association between BRAFV600E gene mutation and tumor-aggressive pathological factors.

METHODS

A total of 42 pediatric patients with papillary thyroid carcinoma who underwent thyroid surgery from 2017 to 2022 were studied retrospectively. Whether the BRAFV600E gene mutation in papillary thyroid carcinoma was related to aggressive biological behavior was analyzed.

RESULTS

Among the 42 pediatric patients with papillary thyroid carcinoma, the median patient age was 15.71 ± 2.51 years (mean ± SD) and the median tumor diameter was 24.95 ± 12.29 mm (mean ± SD). Among all enrolled patients, the mutation rate of the BRAFV600E gene was 54.76% (23 of 42). There were 33 patients with classic papillary thyroid carcinoma, and 22 (66.67%) with classic subtypes were BRAFV600E positive. The BRAFV600E mutation was associated with lower distant metastasis (p = .013) and less Hashimoto's thyroiditis (p = .006). There was no significant difference in clinicopathological factors such as sex, age, tumor size, capsular invasion, multifocality, hypothyroidism, recurrence, lymph node metastasis, and extrathyroidal extension.

CONCLUSIONS

The BRAFV600E mutation is not uncommon in pediatric papillary thyroid carcinoma but is not significantly associated with aggressive biological behavior. It is not possible to determine whether to adopt more active diagnosis and treatment measures on the basis of the mutation of a single BRAFV600E gene.

Children's Oncology Group's 2023 blueprint for research: Rare tumors

The Children's Oncology Group (COG) Rare Tumor Committee includes the Infrequent Tumor and Retinoblastoma subcommittees, encompassing a wide range of extracranial solid tumors that do not fall within another COG disease committee. Current therapeutic trial development focuses on nasopharyngeal carcinoma, adrenocortical carcinoma, pleuropulmonary blastoma, colorectal carcinoma, melanoma, and thyroid carcinoma. Given the rarity of these tumors, novel strategies and international collaborative efforts are necessary to advance research and improve outcomes.

Clinical features of thyroid cancer in paediatric age. Experience of a tertiary centre in the 2000-2020 period

PURPOSE

To describe the clinical features of a paediatric cohort affected by differentiated thyroid cancer (DTC) followed in a tertiary Department of Paediatric Endocrinology.

METHODS

Clinical data of 41 patients affected by DTC in the 2000-2020 period were reviewed.

RESULTS

The main risk factor was autoimmune thyroiditis (39%). Cytological categories were TIR3b in 39%, TIR4 in 9.8%, TIR5 in 51.2%. After total thyroidectomy, radioiodine treatment was performed in 38 subjects (92.7%). ATA low-risk category was assigned in 11 (30.5%), intermediate-risk category in 15 (41.7%), and high-risk category in 10 patients (27.8%). Age at diagnosis was 15.1 ± 0.92 years in low-risk category, 14.7 ± 0.59 in intermediate-risk category, 11.7 ± 0.89 years in high-risk category (p = 0.01). TIR3b was manly observed in low-risk class (63.6%), while TIR5 was mainly reported in intermediate and high-risk class (60 and 80% respectively) (p = 0.04). Post-surgery stimulated thyroglobulin was increased in high-risk class (407.8 ± 307.1 ng/ml) [p = 0.04]. Tumour size was larger in high-risk category (42.6 ± 2.6 mm), than in low and intermediate-risk categories (19.4 ± 3.5 mm and 28.5 ± 3.9 mm, respectively) (p = 0.008). Patients in intermediate and high-risk categories displayed more tumour multifocality (60 and 90% respectively) (p < 0.005). Disease relapse was mainly observed in high risk category (40%, p = 0.04).

CONCLUSION

DTC in childhood is more aggressive than in adults, but the overall survival rate is excellent. The therapeutic approach is still heterogeneous, especially in low-risk category. Further studies are needed to standardise management and reduce disease persistence in childhood.

The Complex Cyto-Molecular Landscape of Thyroid Nodules in Pediatrics

Thyroid fine-needle aspiration (FNA) is a commonly used diagnostic cytological procedure in pediatric patients for the evaluation of thyroid nodules, triaging them for the detection of thyroid cancer. In recent years, greater attention has been paid to thyroid FNA in this setting, including the use of updated ultrasound score algorithms to improve accuracy and yield, especially considering the theoretically higher risk of malignancy of these lesions compared with the adult population, as well as to minimize patient discomfort. Moreover, molecular genetic testing for thyroid disease is an expanding field of research that could aid in distinguishing benign from cancerous nodules and assist in determining their clinical management. Finally, artificial intelligence tools can help in this task by performing a comprehensive analysis of all the obtained data. These advancements have led to greater reliance on FNA as a first-line diagnostic tool for pediatric thyroid disease. This review article provides an overview of these recent developments and their impact on the diagnosis and management of thyroid nodules in children.

Development of Novel Murine BRAFV600E-Driven Papillary Thyroid Cancer Cell Lines for Modeling of Disease Progression and Preclinical Evaluation of Therapeutics

The Cancer Genome Atlas study in thyroid cancer exposed the genomic landscape of ~500 PTCs and revealed BRAFV600E-mutant tumors as having different prognosis, contrasting indolent cases and those with more invasive disease. Here, we describe the generation and characterization of six novel BRAFV600E-driven papillary thyroid cancer (PTC) cell lines established from a BrafV600E+/-/Pten+/-/TPO-Cre mouse model that spontaneously develop thyroid tumors. The novel cell lines were obtained from animals representing a range of developmental stages and both sexes, with the goal of establishing a heterogeneous panel of PTC cell lines sharing a common driver mutation. These cell lines recapitulate the genetics and diverse histopathological features of BRAFV600E-driven PTC, exhibiting differing degrees of growth, differentiation, and invasive potential that may help define mechanisms of pathogenesis underlying the heterogeneity present in the patient population. We demonstrate that these cell lines can be used for a variety of in vitro applications and can maintain the potential for in vivo transplantation into immunocompetent hosts. We believe that these novel cell lines will provide powerful tools for investigating the molecular basis of thyroid cancer progression and will lead to the development of more personalized diagnostic and treatment strategies for BRAFV600E-driven PTC.

Genetic and clinical profiles of 160 papillary thyroid cancers with lateral neck lymph node metastasis

Background

Lymph node metastasis is widespread in papillary thyroid cancer (PTC). Patients are more vulnerable than those with central lymph node metastasis if they have lateral neck lymph node metastasis (LLNM). There are few researches focus on the correlation between clinical characteristics and genetic profile of PTC with LLNM. In this study, we aimed to analyze the clinical and genetic features of PTC with LLNM.

Methods

A total of 160 primary tumor samples derived from PTC patients with LLNM were involved. Targeted next-generation sequencing was carried out on all samples with 57 known thyroid-cancer-related genes. The associations between genomic alternations and clinical characteristics of PTC with LLNM were statistically evaluated.

Results

The median age of patients was 37 years, ranging from 5 to 77 years and the female/male ratio was 1.86. The most frequently altered genes in our series were BRAF mutation (68%), followed by RET fusion (17%), TERT promoter mutation (5%) and PIK3CA mutation (2%). To be noted, all PTC patients with LLNM of TERT promoter mutations appeared along with BRAF mutations (8/8) and half of them experienced a relapse. Intriguingly, we found more metastatic lymph nodes in patients with RET fusion, but there was no statistically significant difference in metastatic lymph node ratio than those with BRAF mutation or without mutation. A high rate of gene fusion (70%) was found in the pediatric population, with aggressive late-onset disease.

Conclusions

PTC patients with LLNM is characterized by a high rate of BRAF mutation. Due to the observed clinicopathological differences in those patients among different alterations, further prospective studies are needed to verify our results and to evaluate the most suitable treatment strategies.

Molecular Landscape of Pediatric Thyroid Cancer: A Review

Thyroid carcinomas (TC) are rare in the pediatric population; however, they constitute the most common endocrine malignancy. Despite some similarities with adult carcinomas, they have distinct clinical behavior and responses to therapy due to their unique pathology and molecular characteristics. The age cut-off used for defining the pediatric age group has been variable across different studies, and the universally accepted recommendations influence accurate interpretation of the available data. Moreover, factors such as radiation exposure and germline mutations have greater impact in children than in adults. Papillary TC is the most common and the most evaluated pediatric TC. Others, including follicular, poorly differentiated and medullary carcinomas, are rarer and have limited available literature. Most studies are from the West. Asian studies are primarily from Japan, with few from China, India, Saudi Arabia and Republic of Korea. This review provides a comprehensive account of the well-established and novel biomarkers in the field, including point mutations, fusions, miRNA, and thyroid differentiation genes. Familial and syndromic associations are also discussed. Current management guidelines for pediatric patients are largely derived from those for adults. An awareness of the molecular landscape is essential to acknowledge the uniqueness of these tumors and establish specific diagnostic and therapeutic guidelines.

2022 European Thyroid Association Guidelines for the management of pediatric thyroid nodules and differentiated thyroid carcinoma

At present, no European recommendations for the management of pediatric thyroid nodules and differentiated thyroid carcinoma (DTC) exist. Differences in clinical, molecular, and pathological characteristics between pediatric and adult DTC emphasize the need for specific recommendations for the pediatric population. An expert panel was instituted by the executive committee of the European Thyroid Association including an international community of experts from a variety of disciplines including pediatric and adult endocrinology, pathology, endocrine surgery, nuclear medicine, clinical genetics, and oncology. The 2015 American Thyroid Association Pediatric Guideline was used as framework for the present guideline. Areas of discordance were identified, and clinical questions were formulated. The expert panel members discussed the evidence and formulated recommendations based on the latest evidence and expert opinion. Children with a thyroid nodule or DTC require expert care in an experienced center. The present guideline provides guidance for healthcare professionals to make well-considered decisions together with patients and parents regarding diagnosis, treatment, and follow-up of pediatric thyroid nodules and DTC.

Molecular testing of cytology specimens: overview of assay selection with focus on lung, salivary gland, and thyroid testing

Ancillary and molecular testing of cytopathology specimens has emerged as a reliable and useful tool to provide diagnostic information and treatment-related biomarker status for the management of cancer patients. The cytology specimens obtained through minimally invasive means have proven suitable testing substrates for a variety of ancillary tests, including immunohistochemistry, fluorescence in situ hybridization, as well as polymerase chain reaction and next generation sequencing molecular techniques. By focusing specifically on the cytology specimen, this review provides an overview of basic testing considerations and assay selection in addition to updates on the ancillary testing of cytologic tumor specimens from the lung, salivary gland, and thyroid.

Differences in the management of thyroid nodules in children and adolescents as compared to adults

PURPOSE OF REVIEW

To describe recent advances in the diagnosis and management of thyroid nodules in both children and adults, highlighting differences between the two groups.

RECENT FINDINGS

Thyroid nodules are less common in children than adults but the risk of malignancy is higher. Screening recommendations for patients with certain genetic syndromes or specific risk factors for thyroid nodules and cancer continue to evolve ultrasound is the most appropriate imaging modality for evaluating thyroid nodules in all patients, but radiographic risk stratification systems validated in adults have not been extensively studied in children. Criteria for proceeding to fine needle aspiration (FNA) biopsy differ some between children and adults, with nodule size being less of a consideration in young patients. Molecular testing continues to improve the diagnostic capabilities of FNA for all age groups, but options for pediatric thyroid nodules are currently limited. In children, only oncogene panels are validated and their exact utility, along with miRNA classifiers, is an evolving area of study. For adults, data support selection of a specific molecular test based on ultrasound characteristics and pretest probability of malignancy. Multiple series have shown that fusion mutations are more common in pediatric thyroid nodules, while point mutations are seen more often in adult thyroid nodules. Molecular data help guide management recommendations regarding the need for surgery when FNA is indeterminate, but clinical use is still being refined. Radiofrequency ablation is a nonoperative approach that has gained significant traction for the treatment of symptomatic benign nodules in adults, but data are currently extremely limited in children.

SUMMARY

There are difference in the diagnosis and treatment of thyroid nodules in adults and children, the nuances of which are important for clinical management.

High Prevalence of Gene Fusions and Copy Number Alterations in Pediatric Radiation Therapy-Induced Papillary and Follicular Thyroid Carcinomas

Background: Childhood cancer survivors and bone marrow transplant recipients treated with radiation therapy (RT) are at increased risk for subsequent thyroid cancer. However, the genetic landscape of pediatric thyroid cancer, both primary and RT-induced, remains poorly defined, as pediatric papillary thyroid carcinoma (PTC) has been understudied compared with adults and data on pediatric follicular thyroid carcinoma (FTC) are virtually nonexistent. The objective of this study was to characterize and compare the molecular profiles of pediatric RT-induced PTC and FTC cases with primary pediatric thyroid cancers. Methods: A total of 41 differentiated thyroid carcinomas (11 RT cases and 30 primary cases) from 37 patients seen at Phoenix Children's Hospital between January 1, 2010 and December 31, 2019 were evaluated by targeted next-generation sequencing and/or BRAF immunohistochemistry. Results: Eighty-six percent (6/7) of RT-PTC harbored a gene fusion (GF) compared with 56% (14/25) of primary PTC; 14% (1/7) of RT-PTC had a single-nucleotide variant (SNV; specifically, a point mutation in the DICER1 gene) compared with 44% (11/25) of primary PTC (all of the latter had the BRAF^V600E mutation). An exceedingly rare ROS1 fusion was identified in a child with RT-PTC. With respect to FTC, copy number alterations (CNAs) were seen in 75% (3/4) of RT cases compared with 40% (2/5) of primary cases. None of the RT-FTC had SNVs compared with 100% (5/5) of primary FTC. Conclusions: In children, the molecular profile of subsequent RT-induced thyroid cancers appears to differ from primary (sporadic and syndromic) cases, with a high prevalence of GFs in RT-PTC (similar to PTC occurring after the Chernobyl nuclear reactor accident) and CNAs in RT-FTC. A better understanding of the molecular mechanisms underlying these cancers may lead to more accurate diagnosis, prognosis, and treatment, as some of the genomic alterations are potentially targetable.

Fusion Oncogenes Are Associated With Increased Metastatic Capacity and Persistent Disease in Pediatric Thyroid Cancers

PURPOSE

In 2014, data from a comprehensive multiplatform analysis of 496 adult papillary thyroid cancer samples reported by The Cancer Genome Atlas project suggested that reclassification of thyroid cancer into molecular subtypes, RAS-like and BRAF-like, better reflects clinical behavior than sole reliance on pathologic classification. The aim of this study was to categorize the common oncogenic variants in pediatric differentiated thyroid cancer (DTC) and investigate whether mutation subtype classification correlated with the risk of metastasis and response to initial therapy in pediatric DTC.

METHODS

Somatic cancer gene panel analysis was completed on DTC from 131 pediatric patients. DTC were categorized into RAS-mutant (H-K-NRAS), BRAF-mutant (BRAF p.V600E), and RET/NTRK fusion (RET, NTRK1, and NTRK3 fusions) to determine differences between subtype classification in regard to pathologic data (American Joint Committee on Cancer TNM) as well as response to therapy 1 year after initial treatment had been completed.

RESULTS

Mutation-based subtype categories were significant in most variables, including age at diagnosis, metastatic behavior, and the likelihood of remission at 1 year. Patients with RET/NTRK fusions were significantly more likely to have advanced lymph node and distant metastasis and less likely to achieve remission at 1 year than patients within RAS- or BRAF-mut subgroups.

CONCLUSION

Our data support that genetic subtyping of pediatric DTC more accurately reflects clinical behavior than sole reliance on pathologic classification with patients with RET/NTRK fusions having worse outcomes than those with BRAF-mutant disease. Future trials should consider inclusion of molecular subtype into risk stratification.

Subtype of atypia on cytology and risk of malignancy in pediatric thyroid nodules

BACKGROUND

Thyroid nodules with atypia of undetermined significance (AUS) are challenging to manage because of their intermediate risk of malignancy. Subclassification of atypia can refine malignancy risk in adult AUS nodules but has not been evaluated in children.

METHODS

This was a retrospective cohort study of pediatric patients (<19 years old) who underwent fine-needle aspiration (FNA) of a thyroid nodule with resulting AUS cytology. Atypia was subclassified as nuclear only, architectural only, nuclear and architectural, or oncocytic. The primary outcome was the association between atypia subtype and malignancy. A secondary outcome was the association of atypia subtype with repeat FNA cytology.

RESULTS

Sixty-eight AUS nodules in 61 patients were analyzed. The median age at FNA was 16.2 years (range, 9.8-18.9 years). Twenty-four nodules (35%) were malignant. Nuclear atypia only was present in 17 nodules (25%), architectural atypia only was present in 27 nodules (40%), nuclear and architectural atypia was present in 20 nodules (29%), and predominantly oncocytic features were present in 4 nodules (6%). The presence of nuclear atypia was associated with a significantly increased rate of malignancy (22 of 37 [59%] vs 2 of 31 [6.5%]; P < .001), whereas architectural atypia was not associated with malignancy (P = .8). Repeat FNA was performed in 42 of 68 nodules (62%). In nodules with initial nuclear and architectural atypia, benign repeat cytology had a high false-negative rate (3 of 6; 50%).

CONCLUSIONS

Pediatric AUS nodules with nuclear atypia have a high rate of malignancy, but architectural atypia is not associated with malignancy. In nodules with nuclear atypia, repeat FNA may inform clinical decisions regarding the need for resection. In the absence of suspicious clinical features, nodules without nuclear atypia might be considered for observation rather than resection or repeat FNA.

Pregnancy has no significant impact on the prognosis of differentiated thyroid cancer

OBJECTIVE

To evaluate the impact of pregnancy on differentiated thyroid carcinomas (DTC) behavior.

METHODS

Retrospective study of patients diagnosed with DTC before or during pregnancy and treated with standard therapy. In women diagnosed with DTC before pregnancy, we evaluated the occurrence of progression according to categories of response to therapy based on imaging and non-stimulated thyroglobulin (TG) levels.

RESULTS

Of 96 analyzed patients, 76 became pregnant after DTC treatment and 20 were diagnosed with DTC during pregnancy. Among women who became pregnant after a DTC diagnosis, no difference was observed regarding response to therapy before and after pregnancy. Disease progression after pregnancy was documented in six of these patients, while seven of them presented progression before pregnancy but were only treated after delivery. Patients with DTC diagnosed during pregnancy had a higher rate of distant metastases at diagnosis (30%) compared with the patients who became pregnant after DTC diagnosis (9.2%, p = 0.01).

CONCLUSION

Pregnancy had no impact on the natural course of DTC. Disease progression after pregnancy was limited and probably related to more aggressive disease and higher risk stratification at diagnosis. Still, mild disease progression may have occurred asymptomatically in some patients.

Prevalence and Risk Factors for Multifocality in Pediatric Thyroid Cancer

Importance

Current guidelines recommend total thyroidectomy for the majority of pediatric thyroid cancer owing to an increased prevalence of multifocality. However, there is a paucity of information on the exact prevalence and risk factors for multifocal disease-knowledge that is critical to improving pediatric thyroid cancer management and outcomes.

Objective

To determine the prevalence and risk factors for multifocal disease in pediatric patients with papillary thyroid carcinoma (PTC).

Design, Setting, and Participants

This multicenter retrospective cohort study included patients 18 years or younger who underwent thyroidectomy for PTC from 2010 to 2020 at 3 tertiary pediatric hospitals and 2 tertiary adult and pediatric hospitals in the US.

Main Outcomes and Measures

Demographic and clinical variables, including age, family history of thyroid cancer, autoimmune thyroiditis, prior radiation exposure, cancer predisposition syndrome, tumor size, tumor and nodal stage, PTC pathologic variant, and preoperative imaging, were assessed for association with presence of any multifocal, unilateral multifocal, and bilateral multifocal disease using multiple logistic regression analyses. Least absolute shrinkage and selection operator analysis was performed to develop a model of variables that may predict multifocal disease.

Results

Of 212 patients, the mean age was 14.1 years, with 23 patients 10 years or younger; 173 (82%) patients were female. Any multifocal disease was present in 98 (46%) patients, with bilateral multifocal disease in 73 (34%). Bilateral multifocal disease was more accurately predicted on preoperative imaging than unilateral multifocal disease (48 of 73 [66%] patients vs 9 of 25 [36%] patients). Being 10 years or younger, T3 tumor stage, and N1b nodal stage were identified as predictors for multifocal and bilateral multifocal disease.

Conclusions and Relevance

This large, multicenter cohort study demonstrated a high prevalence of multifocal disease in pediatric patients with PTC. Additionally, several potential predictors of multifocal disease, including age and advanced T and N stages, were identified. These risk factors and the high prevalence of multifocal disease should be considered when weighing the risks and benefits of surgical management options in pediatric patients with PTC.

Diverse Oncogenic Fusions and Distinct Gene Expression Patterns Define the Genomic Landscape of Pediatric Papillary Thyroid Carcinoma

Pediatric papillary thyroid carcinoma (PPTC) is clinically distinct from adult-onset disease. Although there are higher rates of metastasis and recurrence in PPTC, prognosis remains highly favorable. Molecular characterization of PPTC has been lacking. Historically, only 40% to 50% of childhood papillary thyroid carcinoma (PTC) were known to be driven by genomic variants common to adult PTC; oncogenic drivers in the remainder were unknown. This contrasts with approximately 90% of adult PTC driven by a discrete number of variants. In this study, 52 PPTCs underwent candidate gene testing, followed in a subset by whole-exome and transcriptome sequencing. Within these samples, candidate gene testing identified variants in 31 (60%) tumors, while exome and transcriptome sequencing identified oncogenic variants in 19 of 21 (90%) remaining tumors. The latter were enriched for oncogenic fusions, with 11 nonrecurrent fusion transcripts, including two previously undescribed fusions, STRN-RET and TG-PBF. Most fusions were associated with 3' receptor tyrosine kinase (RTK) moieties: RET, MET, ALK, and NTRK3. For advanced (distally metastatic) tumors, a driver variant was described in 91%. Gene expression analysis defined three clusters that demonstrated distinct expression of genes involved in thyroid differentiation and MAPK signaling. Among RET-CCDC6-driven tumors, gene expression in pediatric tumors was distinguishable from that in adults. Collectively, these results show that the genomic landscape of pediatric PTC is different from adult PTC. Moreover, they identify genomic drivers in 98% of PPTCs, predominantly oncogenic fusion transcripts involving RTKs, with a pronounced impact on gene expression. Notably, most advanced tumors were driven by a variant for which targeted systemic therapy exists. SIGNIFICANCE: This study highlights important distinctions between the genomes and transcriptomes of pediatric and adult papillary thyroid carcinoma, with implications for understanding the biology, diagnosis, and treatment of advanced disease in children.

Oncogene-specific inhibition in the treatment of advanced pediatric thyroid cancer

Papillary thyroid cancer (PTC) is the most common form of differentiated thyroid cancer in the pediatric population and represents the second most common malignancy in adolescent females. Historically, PTC has been classified on the basis of histology, however, accumulating data indicate that molecular subtyping based on somatic oncogenic alterations along with gene expression profiling can better predict clinical behavior and may provide opportunities to incorporate oncogene-specific inhibitory therapy to improve the response to radioactive iodine (RAI). In this issue of the JCI, Y.A. Lee, H. Lee, and colleagues showed that oncogenic fusions were more commonly associated with invasive disease, increased expression of MAPK signaling pathway genes (ERK score), and decreased expression of the sodium-iodine symporter, which was restored by RET- and NTRK-inhibitory therapy. These findings lend credence to the idea of reclassifying pediatric thyroid cancers using a three-tiered system, rather than the two-tiered adult system, and open avenues for the treatment of progressive, RAI-refractory PTC in patients.

NTRK- and RET-fusion-directed therapy in pediatric thyroid cancer yields a tumor response and radioiodine uptake

BACKGROUND

Molecular characterization in pediatric papillary thyroid cancer (PTC), distinct from adult PTC, is important for developing molecular targeted therapies for progressive 131I-refractory PTC.

METHODS

PTC samples from 106 pediatric patients (age: 4.3-19.8 years; 21 boys) who attended Seoul National University Hospital (January 1983-March 2020) were available for genomic profiling. Previous transcriptome data from 125 adult PTCs were used for comparison.

RESULTS

Genetic drivers were found in 80 tumors; 31 with fusion oncogenes (RET in 21, ALK in 6, and NTRK1/3 in 4), 47 with point mutations (BRAFV600E in 41, TERTC228T in 2, and DICER1 variants in 5), and 2 with amplifications. Fusion-oncogene PTCs, predominantly detected in younger patients, presented with a more advanced stage and showed more recurrent or persistent disease than BRAFV600E PTCs, which were detected mostly in adolescents. Pediatric fusion PTCs (in those aged < 10 years) showed lower expression of thyroid differentiation genes, including SLC5A5, than adult fusion PTCs. Two girls with progressive 131I-refractory lung metastases harboring a TPR-NTRK1 or CCDC6-RET fusion received fusion-targeted therapy; larotrectinib and selpercatinib decreased the tumor extent and restored radioiodine uptake. The girl with the CCDC6-RET fusion received 131I therapy combined with selpercatinib, leading to a tumor response. In vitro 125I uptake and 131I clonogenic assays showed that larotrectinib inhibited growth and restored radioiodine avidity.

CONCLUSIONS

In pediatric fusion-oncogene PTC cases with 131I-refractory advanced disease, selective fusion-directed therapy may restore radioiodine avidity and lead to a dramatic tumor response, underscoring the importance of molecular testing in pediatric PTC patients.

FUNDING

The Ministry of Science, ICT & Future Planning (grant number NRF-2016R1A2B4012417 91 and 2019R1A2C2084332), the Ministry of Health & Welfare, Republic of Korea (grant number 92 H14C1277), the Ministry of Education (grant number 2020R1A6A1A03047972), and the Seoul 93 National University Hospital Research Fund (grant number 04-2015-0830).

Distant Metastases From Childhood Differentiated Thyroid Carcinoma: Clinical Course and Mutational Landscape

CONTEXT

Distant metastases (DM) from childhood differentiated thyroid carcinoma (DTC) are uncommon and published studies are limited.

OBJECTIVE

This work aimed to describe the outcomes of patients with DM from childhood DTC and to evaluate the molecular landscape of these tumors.

METHODS

A retrospective study was conducted at a tertiary cancer center including patients with pediatric DTC (diagnosed at age ≤ 18 years from 1946 to 2019) and DM.

RESULTS

We identified 148 patients; 144 (97%) had papillary thyroid carcinoma (PTC) and 104 (70%) were female. Median age at DTC diagnosis was 13.4 years (interquartile range [IQR], 9.9-15.9 years). Evaluable individuals received a median of 2 (IQR, 1-3) radioactive iodine (RAI) treatments at a median cumulative administered activity of 238.0 mCi (IQR, 147.5-351.0 mCi). The oncogenic driver was determined in 64 of 69 PTC samples: RET fusion (38/64; 59%), NTRK1/3 fusions (18/64; 28%), and the BRAF V600E mutation (8/64; 13%). At last evaluation, 93% had persistent disease. The median overall and disease-specific survival after DTC diagnosis were 50.7 and 52.8 years, respectively. Eight (5%) PTC patients died of disease after a median of 30.7 years (IQR, 20.6-37.6 years).

CONCLUSION

Childhood DTC with DM persists in most patients despite multiple courses of RAI, but disease-specific death is uncommon, typically occurring decades after diagnosis. Fusion genes are highly prevalent in PTC, and all identified molecular alterations have appropriate targeted therapies. Future studies should focus on expanding genotype-phenotype correlations, determining how to integrate molecularly targeted therapy into treatment paradigms, and relying less on repeated courses of RAI to achieve cure in patients with DM from childhood DTC.

Management of Differentiated Thyroid Carcinoma in Pediatric Patients

Differentiated thyroid carcinomas are rare in young children but represent almost 10% of all malignancies diagnosed in older adolescents. Differentiated thyroid carcinoma in children is more likely to demonstrate nodal involvement and is associated with higher recurrence rates than seen in adults. Decisions regarding extent of surgical resection are based on clinical and radiologic features, cytology, and risk assessment. Total thyroidectomy and compartment-based resection of involved lymph node basins form the cornerstone of treatment. The use of molecular genetics to inform treatment strategies and the use of targeted therapies to unresectable progressive disease is evolving.

NTRK Fusions Identified in Pediatric Tumors: The Frequency, Fusion Partners, and Clinical Outcome

Neurotrophic tyrosine receptor kinase (NTRK) fusions have been described as oncogenic drivers in a variety of tumors. However, little is known about the overall frequency of NTRK fusion in unselected pediatric tumors. Here, we assessed the frequency, fusion partners, and clinical course in pediatric patients with NTRK fusion–positive tumors.

Canadian Consensus for Biomarker Testing and Treatment of TRK Fusion Cancer in Pediatric Patients

Neurotrophic tyrosine receptor kinase gene fusions (NTRK) are oncogenic drivers present at a low frequency in most tumour types (<5%), and at a higher frequency (>80%) in a small number of rare tumours (e.g., infantile fibrosarcoma [IFS]) and considered mutually exclusive with other common oncogenic drivers. Health Canada recently approved two tyrosine receptor kinase (TRK) inhibitors, larotrectinib (for adults and children) and entrectinib (for adults), for the treatment of solid tumours harbouring NTRK gene fusions. In Phase I/II trials, these TRK inhibitors have demonstrated promising overall response rates and tolerability in patients with TRK fusion cancer who have exhausted other treatment options. In these studies, children appear to have similar responses and tolerability to adults. In this report, we provide a Canadian consensus on when and how to test for NTRK gene fusions and when to consider treatment with a TRK inhibitor for pediatric patients with solid tumours. We focus on three pediatric tumour types: non-rhabdomyosarcoma soft tissue sarcoma/unspecified spindle cell tumours including IFS, differentiated thyroid carcinoma, and glioma. We also propose a tumour-agnostic consensus based on the probability of the tumour harbouring an NTRK gene fusion. For children with locally advanced or metastatic TRK fusion cancer who have either failed upfront therapy or lack satisfactory treatment options, TRK inhibitor therapy should be considered.

Integrated DNA and RNA sequencing reveals targetable alterations in metastatic pediatric papillary thyroid carcinoma

BACKGROUND

Pediatric papillary thyroid carcinoma (PTC) is clinically and biologically distinct from adult PTC. We sequenced a cohort of clinically annotated pediatric PTC cases enriched for high-risk tumors to identify genetic alterations of relevance for diagnosis and therapy.

METHODS

Tumor DNA and RNA were extracted from FFPE tissue and subjected to next-generation sequencing (NGS) library preparation using a custom 124-gene hybridization capture panel and the 75-gene Archer Oncology Research Panel, respectively. NGS libraries were sequenced on an Illumina MiSeq.

RESULTS

Thirty-six pediatric PTC cases were analyzed. Metastases were frequently observed to cervical lymph nodes (29/36, 81%), with pulmonary metastases less commonly found (10/36, 28%). Relapsed or refractory disease occurred in 18 patients (18/36, 50%). DNA sequencing revealed targetable mutations in 8 of 31 tumors tested (26%), most commonly BRAF p.V600E (n = 6). RNA sequencing identified targetable fusions in 13 of 25 tumors tested (52%): RET (n = 8), NTRK3 (n = 4), and BRAF. Mutually exclusive targetable alterations were discovered in 15 of the 20 tumors (75%) with both DNA and RNA analyzed. Fusion-positive PTC was associated with multifocal disease, higher tumor staging, and higher American Thyroid Association risk levels. Both BRAF V600E mutations and gene fusions were correlated with the presence of cervical metastases.

CONCLUSIONS

Targetable alterations were identified in 75% of pediatric PTC cases with both DNA and RNA evaluated. Inclusion of RNA sequencing for detection of fusion genes is critical for evaluation of these tumors. Patients with fusion-positive tumors were more likely to have features of high-risk disease.

Consensus statement by the American Association of Clinical Endocrinology (AACE) and the American Head and Neck Society Endocrine Surgery Section (AHNS-ES) on Pediatric Benign and Malignant Thyroid Surgery

OBJECTIVES

To provide a clinical disease state review of recent relevant literature and to generate expert consensus statements regarding the breadth of pediatric thyroid cancer diagnosis and care, with an emphasis on thyroid surgery. To generate expert statements to educate pediatric practitioners on the state-of-the-art practices and the value of surgical experience in the management of this unusual and challenging disease in children.

METHODS

A literature search was conducted and statements were constructed and subjected to a modified Delphi process to measure the consensus of the expert author panel. The wording of statements, voting tabulation, and statistical analysis were overseen by a Delphi expert (J.J.S.).

RESULTS

Twenty-five consensus statements were created and subjected to a modified Delphi analysis to measure the strength of consensus of the expert author panel. All statements reached a level of consensus, and the majority of statements reached the highest level of consensus.

CONCLUSION

Pediatric thyroid cancer has many unique nuances, such as bulky cervical adenopathy on presentation, an increased incidence of diffuse sclerosing variant, and a longer potential lifespan to endure potential complications from treatment. Complications can be a burden to parents and patients alike. We suggest that optimal outcomes and decreased morbidity will come from the use of advanced imaging, diagnostic testing, and neural monitoring of patients treated at high-volume centers by high-volume surgeons.

Papillary thyroid carcinoma in children with Hashimoto's thyroiditis - a review of the literature between 2000 and 2020

OBJECTIVES

Thyroid cancer is the most common pediatric endocrine neoplasm representing 3% of all malignancies in children. Hashimoto's thyroiditis (HT) is also a common disorder in the pediatric age range. Patients with HT frequently develop enlarged thyroid with nodules. We aimed to provide a literature review on the frequency of papillary thyroid carcinoma (PTC) in patients with HT.

CONTENT

A literature search of the PubMed database between 2000 and 2020 was performed, using the relevant keywords "papillary thyroid carcinoma," "Hashimoto's thyroiditis" and "children". We followed the PRISMA statement guidelines during the preparation of this review. Six studies (n=2,065 patients with HT) were retained for the final analysis. The follow-up of the patients with HT was from 2 to 10 years. PTC was diagnosed in 0.67-7.87% of the HT patients included in these studies. In patients with HT and nodules, the percentage of PTC varied between 5.13 and 35%. The overall occurrence of PTC in patients with HT was 3.07%.

SUMMARY AND OUTLOOK

The number of patients developing thyroid nodules in relation to HT was increased. The development of PTC in children with HT appeared to be higher than in the normal population.

Consensus Statement by the American Association of Clinical Endocrinology (AACE) and the American Head and Neck Society Endocrine Surgery Section (AHNS) on Pediatric Benign and Malignant Thyroid Surgery

OBJECTIVES

To provide a clinical disease state review of recent relevant literature and to generate expert consensus statements regarding the breadth of pediatric thyroid cancer diagnosis and care, with an emphasis on thyroid surgery. To generate expert statements to educate pediatric practitioners on the state-of-the-art practices and the value of surgical experience in the management of this unusual and challenging disease in children.

METHODS

A literature search was conducted and statements were constructed and subjected to a modified Delphi process to measure the consensus of the expert author panel. The wording of statements, voting tabulation, and statistical analysis were overseen by a Delphi expert (J.J.S.).

RESULTS

Twenty-five consensus statements were created and subjected to a modified Delphi analysis to measure the strength of consensus of the expert author panel. All statements reached a level of consensus, and the majority of statements reached the highest level of consensus.

CONCLUSION

Pediatric thyroid cancer has many unique nuances, such as bulky cervical adenopathy on presentation, an increased incidence of diffuse sclerosing variant, and a longer potential lifespan to endure potential complications from treatment. Complications can be a burden to parents and patients alike. We suggest that optimal outcomes and decreased morbidity will come from the use of advanced imaging, diagnostic testing, and neural monitoring of patients treated at high-volume centers by high-volume surgeons.

Pediatric Thyroid Cancer: Genetics, Therapeutics and Outcome

An increasing number of children are diagnosed with thyroid cancer. Most patients do not have an identifiable cause; however, tumor predisposition syndromes may be associated with development of both differentiated and medullary thyroid cancer. With an excellent prognosis for most patients, the goal of therapy is to optimize outcome and reduce complications. The increased knowledge of the oncogenic drivers provides opportunities to improve the accuracy of diagnosis, stratify surgery, and select systemic therapy that may be considered for neoadjuvant and adjuvant treatment. Treatment complications can be reduced by referral to regional, high-volume pediatric thyroid centers.

Pediatric differentiated thyroid carcinoma: An update from the APSA Cancer Committee

BACKGROUND

Differentiated thyroid carcinomas (DTCs) are rare in young children but represent almost 10% of all malignancies diagnosed in older adolescents.

METHODS

This article reviews the recent literature describing surgical therapeutic approaches to pediatric DTC, associated complications, and long-term recurrence and survival outcomes.

RESULTS

Similar to adult thyroid cancers, pediatric DTCs are more common in females and are associated with thyroid nodules, family history of thyroid cancer, radiation exposure, iodine deficiency, autoimmune thyroid disease, and genetic syndromes. Management of thyroid cancers in children involves ultrasound imaging, fine needle aspiration, and surgical resection with treatment decisions based on clinical and radiological features, cytology and risk assessment.

CONCLUSIONS

Total thyroidectomy and compartment based resection of clinically involved lymph node basins form the cornerstone of treatment of DTC. There is an evolving literature regarding the use of molecular genetics to inform treatment strategies and the use of targeted therapies to treat iodine refractory and surgically unresectable progressive disease.

TYPE OF STUDY

Summary review.

LEVEL OF EVIDENCE

This is a review article of previously published Level 1-5 articles that includes expert opinion (Level 5).

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.

Papillary and Follicular Thyroid Cancer in children and adolescents: Current approach and future directions

An increasing number of children are diagnosed with differentiated thyroid cancer. With an excellent prognosis for the majority of pediatric patients, the goal of therapy is to optimize outcome while reducing complications. Increased knowledge of the somatic, oncogenic driver mutations provides opportunities to improve the accuracy of diagnosis, to stratify surgery, and to treat patients with morbidly invasive or refractory disease. Treatment complications can be reduced by referral to regional, high-volume pediatric thyroid centers.

miRNA expression can classify pediatric thyroid lesions and increases the diagnostic yield of mutation testing

BACKGROUND

Genetic alterations in multiple cell signaling pathways are involved in the molecular pathogenesis of thyroid cancer. Oncogene mutation testing and gene-expression profiling are routinely used for the preoperative risk management of adult thyroid nodules. In this study, we evaluated the potential value of miRNA biomarkers for the classification of pediatric thyroid lesions.

PROCEDURE

Double-blind case-control study with 113 resected pediatric lesions: 66 malignant and 47 benign. Quantitative and qualitative molecular data generated with a 10-miRNA expression panel (ThyraMIR) and a next-generation sequencing oncogene panel (ThyGeNEXT) were compared with clinicopathological parameters.

RESULTS

miRNAs were differentially expressed in benign versus malignant tumors with distinct expression patterns in different histopathology categories. The 10-miRNA classifier identified 39 (59%) malignant lesions with 100% specificity. A positive classifier score was associated with lymph node metastasis, extrathyroidal extension and intrathyroidal spread. Genetic alterations associated with increased risk for malignancy were detected in 35 (53%) malignant cases, 20 positive for point mutations in BRAF, HRAS, KRAS, NRAS, PIK3CA, or TERT and 15 positive for gene rearrangements involving ALK, NTRK3, PPARG, or RET. The 10-miRNA classifier correctly identified 11 mutation-negative malignant cases. The performance of the combined molecular test was 70% sensitivity and 96% specificity with an area under the curve of 0.924.

CONCLUSIONS

These data suggest that the regulatory miRNA pathways underlying thyroid tumorigenesis are similar in adults and children. miRNA expression can identify malignant lesions with high specificity, augment the diagnostic yield of mutation testing, and improve the molecular classification of pediatric thyroid nodules.

Thyroid nodules in children and adolescents

PURPOSE OF REVIEW

Compared with adults, there is a two-fold to three-fold increased risk of malignancy for a pediatric patient undergoing evaluation of a thyroid nodule. In 2015, the American Thyroid Association published guidelines on the evaluation and management of pediatric patients with thyroid nodules and differentiated thyroid cancer. The goal of this clinical update is to review recent additions to the literature and propose opportunities how to best incorporate these findings into clinical practice.

RECENT FINDINGS

Recent additions to the literature include assessment of ultrasound-based scoring systems to improve selection of patients for fine needle aspiration, defining the pediatric-specific risk of malignancy within The Bethesda System for Reporting Thyroid Cytopathology, and broadening our knowledge of the oncogene landscape that supports incorporation of adjunct oncogene testing to rule-in malignancy of nodules with indeterminate cytology.

SUMMARY

There have been significant additions to the literature on the evaluation and management of children and adolescents with thyroid nodules since publication of the 2015 American Thyroid Association guidelines. Incorporating these changes into clinical care, within the setting of multidisciplinary, pediatric-specific, regional centers, will maximize ongoing efforts to improve the care of children and adolescents with thyroid nodules.

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.

Management outcomes of pediatric and adolescent papillary thyroid cancers with a brief review of literature

Background

Papillary carcinoma of thyroid (PTC) is a rare disease in children and adolescents and contributes to about 1.5%-3% of all pediatric malignancies. To date, no randomized trial has ever been performed in the pediatric population and management of these patients has been extrapolated from adult practice.

Materials and Methods

Retrospective analysis of the patients treated for PTC in the age <21 years, between the years 1998-2013 at a tertiary cancer center from India.

Results

Sixty-seven patients were treated in the above said period with a male:female ratio of 1:1.6 and a median age of 18 years. Fifty-two (77.6%) patients clinically presented as a thyroid swelling with or without nodal swelling while 13 (19.4%) presented with isolated nodal swelling. Surgery was performed in 30 patients at a nononcological hospital and was subsequently referred to our center; more than half of them needed a completion surgery at our center. Pathologically, multifocal tumors were found in close to a quarter of the patients. Among the pathological variants, classical, follicular, and tall cell variants comprised 65.7%, 28.4%, and 5.9% of the cases, respectively. Nodal positivity was noted 71.6% of the cases of which 14.5% were N1a disease and the vast majority (85.5%) harboring N1b disease. The median follow-up period of the study cohort was 104 months during which there were 3 local, 6 nodal, and 2 systemic recurrences. The 5- and 10-year disease-free survival were found to be 85.9% and 81.4%, respectively. Univariate and multivariate analysis has shown no significant clinical and pathological feature defining the disease outcomes except for the T-stage. Logistic regression revealed extrathyroidal invasion and the age ≤ 15 years correlated with nodal positivity.

Conclusion

Being a rare malignancy, pediatric and adolescent PTCs tend to behave differently from adult PTC with a seemingly aggressive clinical presentation; however, they are associated with excellent survival outcomes.

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.