Clinically-relevant Germline Variants in Children with Non-Medullary Thyroid Cancer.

CONTEXT: The underlying genetic cause of non-medullary thyroid cancer (NMTC) in children is often unknown, hampering both predictive testing of family members and preventive clinical management. OBJECTIVE: Our objectives were to investigated the potential heritability in the largest childhood NMTC cohort that has been genotyped to date. DESIGN: Nationwide retrospective cohort study. SETTING: Tertiary referral centers. PATIENTS: In total, 97 patients diagnosed with pediatric NMTC between 1970-2020 were included in this study. INTERVENTION: Germline whole genome sequencing (WGS). MAIN OUTCOME: The main outcome measures were mutation detection yield in 1) clinically-relevant tumor predisposition genes, and 2) genes previously associated with NMTC. RESULTS: In total, 13 of 97 patients (13%) carried a germline (likely) pathogenic (P/LP) variant in a well-known tumor predisposition gene: APC (n=1), BRCA2 (n=2), CHEK2 (n=4), DICER1 (n=4), HOXB13 (n=1), , and MITF (n=1). In addition, one patient was diagnosed with Pendred syndrome (SLC26A4) and nine variants of high interest were found in other NMTC candidate susceptibility genes. CONCLUSION: The reported prevalence (13%) of germline variants in well-known tumor predisposing genes and the added value of a revised personal-/family history and histology led us to recommend genetic counseling for all childhood NMTC patients.The detected tumor predisposition syndromes are associated with a risk for second cancers which necessitates additional surveillance of the index patients and pre-symptomatic genetic testing of at risk family members.

SDHB variant type impacts phenotype and malignancy in pheochromocytoma-paraganglioma.

BACKGROUND: Traditional genotype-phenotype correlations for the succinate dehydrogenase-complex II (SDH) genes link SDHB variants to thoracic-abdominal pheochromocytoma-paraganglioma (PPGL) and SDHD variants to head and neck paraganglioma (HNPGL). However, in a recent study we found strong and specific genotype-phenotype associations for SDHD variants. In the present study we zoom in on the genotype-phenotype associations of SDHB gene variants, considering the impact of individual gene variants on disease risk and risk of malignancy. METHODS: We analysed two large independent data sets, including a total of 448 patients with PPGL and HNPGL, and studied the association of missense or truncating SDHB variants with tumour incidence, age of onset and malignancy risk using binomial testing and Kaplan-Meier analysis. RESULTS: Compared with missense variants, truncating SDHB variants were significantly and consistently more common in patients with PPGL, by a 20 percentage point margin. Malignancy was also significantly more common in truncating versus missense variant carriers. No overall differences in age of PPGL onset were noted between carriers of the two variant types, although some individual variants may differ in certain cases. Missense variants were marginally over-represented among patients with HNPGL, but the difference was not statistically significant. CONCLUSION: SDHB truncating variants convey an elevated risk for development of both PPGL and malignancy compared with missense variants. These results further support earlier robust associations between truncating variants and PPGL, and also suggest that the two variant types differ in their impact on complex II function, with PPGL/HNPGL tissues displaying differing sensitivities to changes in complex II function.

Surveillance recommendations for DICER1 pathogenic variant carriers: a report from the SIOPE Host Genome Working Group and CanGene-CanVar Clinical Guideline Working Group.

DICER1 syndrome is a rare genetic disorder that predisposes to a wide spectrum of tumors. Developing surveillance protocols for this syndrome is challenging because uncertainty exists about the clinical efficacy of surveillance, and appraisal of potential benefits and harms vary. In addition, there is increasing evidence that germline DICER1 pathogenic variants are associated with lower penetrance for cancer than previously assumed. To address these issues and to harmonize DICER1 syndrome surveillance programs within Europe, the Host Genome Working Group of the European branch of the International Society of Pediatric Oncology (SIOPE HGWG) and Clinical Guideline Working Group of the CanGene-CanVar project in the United Kingdom reviewed current surveillance strategies and evaluated additional relevant literature. Consensus was achieved for a new surveillance protocol and information leaflet that informs patients about potential symptoms of DICER1-associated tumors. The surveillance protocol comprises a minimum program and an extended version for consideration. The key recommendations of the minimum program are: annual clinical examination from birth to age 20 years, six-monthly chest X-ray and renal ultrasound from birth to age 6 years, and thyroid ultrasound every 3 years from age 8 to age 40 years. The surveillance program for consideration comprises additional surveillance procedures, and recommendations for DICER1 pathogenic variant carriers outside the ages of the surveillance interval. Patients have to be supported in choosing the surveillance program that best meets their needs. Prospective evaluation of the efficacy and patient perspectives of proposed surveillance recommendations is required to expand the evidence base for DICER1 surveillance protocols.

Clinical and Molecular Characteristics May Alter Treatment Strategies of Thyroid Malignancies in DICER1 Syndrome.

Context: DICER1 syndrome is a rare autosomal-dominantly inherited disorder that predisposes to a variety of cancerous and noncancerous tumors of mostly pediatric and adolescent onset, including differentiated thyroid carcinoma (DTC). DTC has been hypothesized to arise secondarily to the increased prevalence of thyroid hyperplastic nodules in syndromic patients. Objective: To determine somatic alterations in DICER1-associated DTC and to study patient outcomes. Design: Retrospective series. Setting: Tertiary referral centers. Patients: Ten patients with germline pathogenic DICER1 variants and early-onset DTC. Methods: Somatic DICER1 mutation analysis, extensive somatic DNA variant and gene fusion analyses were performed on all tumors. Results: Median age at DTC diagnosis was 13.5 years and there was no recurrent or metastatic disease (median follow-up, 8 years). All thyroid specimens showed diffuse nodular hyperplasia with at least one focus suspicious of DTC but without infiltrative growth, extrathyroidal extension, vascular invasion, or lymph node metastasis. Most of the individual nodules (benign and malignant) sampled from the 10 tumors harbored distinct DICER1 RNase IIIb hotspot mutations, indicating a polyclonal composition of each tumor. Furthermore, nine of 10 DICER1-related DTCs lacked well-known oncogenic driver DNA variants and gene rearrangements. Conclusion: On the basis of our clinical, histological, and molecular data, we consider that most DICER1-related DTCs form a low-risk subgroup. These tumors may arise within one of multiple benign monoclonal nodules; thus, hemi-thyroidectomy or, more likely, total thyroidectomy may often be required. However, radioiodine treatment may be unnecessary given the patients' ages and the tumors' low propensity for metastases.

Clinical Aspects of SDHA-Related Pheochromocytoma and Paraganglioma: A Nationwide Study.

Context: Paraganglioma (PGL) has the highest degree of heritability among human neoplasms. Current clinical understanding of germline SDHA mutation carriers is limited. Objective: To estimate the contribution of SDHA mutations in PGL and to assess clinical manifestations and age-related penetrance. Design: Nationwide retrospective cohort study. Setting: Tertiary referral centers in the Netherlands (multicenter). Patients: Germline SDHA analysis was performed in 393 patients with genetically unexplained PGL. Subsequently, 30 index SDHA mutation carriers and 56 nonindex carriers were studied. Main Outcome Measures: SDHA mutation detection yield, clinical manifestations, and SDHA-related disease penetrance. Results: Pathogenic germline SDHA variants were identified in 30 of the 393 referred patients with PGL (7.6%), who had head and neck PGL (21 of 174 [12%]), pheochromocytoma (4 of 191 [2%]), or sympathetic PGL (5 of 28 [18%]). The median age at diagnosis was 43 years (range, 17 to 81 years) in index SDHA mutation carriers compared with 52 years (range, 7 to 90 years) in nonmutation carriers (P = 0.002). The estimated penetrance of any SDHA-related manifestation was 10% at age 70 years (95% confidence interval, 0% to 21%) in nonindex mutation carriers. Conclusion: Germline SDHA mutations are relatively common (7.6%) in patients with genetically unexplained PGL. Most index patients presented with apparently sporadic PGL. In this SDHA series, the largest assembled so far, we found the lowest penetrance of all major PGL predisposition genes. This suggests that recommendations for genetic counseling of at-risk relatives and stringency of surveillance for SDHA mutation carriers might need to be reassessed.

CDC73-Related Disorders: Clinical Manifestations and Case Detection in Primary Hyperparathyroidism.

Context: Heterozygous pathogenic germline variants in CDC73 predispose to the development of primary hyperparathyroidism (pHPT) and, less frequently, ossifying fibroma of the jaw and renal and uterine tumors. Clinical information on CDC73-related disorders has so far been limited to small case series. Objective: To assess the clinical manifestations and penetrance in CDC73-related disorders and to improve case detection in pHPT. Design: Nationwide retrospective Dutch cohort study. Setting: Tertiary referral center. Patients: We studied 89 patients with pHPT referred for germline CDC73 analysis and 43 subsequently tested relatives who proved to be mutation carriers. Investigation: Germline CDC73 mutation analysis. Mean Outcome: CDC73 mutation detection yield, referral rate, and CDC73-related disease penetrance. Results: Pathogenic germline CDC73 variants were identified in 11 of the 89 referred pHPT patients (12.4%), with (suspected) hyperparathyroidism-jaw tumor (HPT-JT) syndrome (n = 3), familial isolated pHPT (n = 5), apparently sporadic parathyroid carcinoma (n = 2), and apparently sporadic parathyroid adenoma (n = 1). The estimated penetrance of CDC73-related disorders was 65% at age 50 years (95% confidence interval, 48% to 82%) in 43 nonindex mutation carriers. Conclusions: Germline CDC73 analysis is recommended in individuals with (suspected) HPT-JT syndrome, familial isolated pHPT, atypical or malignant parathyroid histology, and young individuals with pHPT. These criteria would increase germline CDC73 mutation detection, enabling optimal clinical management of pHPT as well as genetic counseling and surveillance for family members at risk for developing CDC73-related disorders.