DICER1 Variants Research Articles

Health-related quality of life in children and adolescents with pleuropulmonary blastoma: A report from the International PPB/DICER1 Registry.

Pleuropulmonary blastoma (PPB) is the most common lung cancer of infancy and early childhood and is associated with germline DICER1 variants. Type I and Ir PPB are cystic lesions treated surgically, with a subset of children with type I receiving chemotherapy. Type II and III are more aggressive lesions, treated with surgery, intensive chemotherapy and potentially radiation. We sought to assess health-related quality of life (HRQoL) in children with PPB and known germline DICER1 variants. Children with a diagnosis of PPB or germline DICER1 pathogenic variant without history of PPB or other DICER1-related neoplasm (DICER1+ only) were enrolled in the International PPB/DICER1 Registry. Parent reports for participants aged 2-17years for the PedsQL v.4 and PedsQL Multidimensional Fatigue Scale v.3 were collected. Fatigue, physical, and psychosocial function scores were compared. Analysis included 84 participants (PPB type Ir=20, type I=15, type II/III=27, DICER1+ only=22). Total fatigue scores of participants with type I and II/III PPB were lower compared to DICER1+ only, with effect size larger in type II/III (-0.82 vs. -0.40). Total psychosocial and physical functioning scores were lower in participants with type I and type II/III PPB compared to DICER1+ only, with larger effects noted in type II/III. Female sex was suggestive of worse HRQoL for both type I/Ir and type II/III cohorts. These data demonstrate the importance of regular HRQoL assessment in patients with a history of PPB as well as the importance and feasibility of studying HRQoL in children with rare tumors.

Evidence of neural crest cell origin of a DICER1 mutant CNS sarcoma in a child with DICER1 syndrome and NRAS-mutant neurocutaneous melanosis.

Evidence of neural crest cell origin of a DICER1 mutant CNS sarcoma in a child with DICER1 syndrome and NRAS-mutant neurocutaneous melanosis.

Prevalence and spectrum analysis of germline DICER1 variants of solid tumors: Decoding the mysterious signals of the genome.

10578 Background: DICER1 syndrome is a rare genetic condition predisposing to multiple cancer types and causes by germline DICER1 variants. Deleterious mutations identified were mostly located in the RNase III domain. VUSs found in other domains may be also crucial in the inheritance of high-risk neoplasms although there is insufficient evidence. Our study aimed at describing the spectrum of DICER1 variants detected in solid tumors to improve the identification of potentially high-risk DICER1 variants. Methods: Germline mutations including SNV, small INDEL in 448 patients with solid tumors were analyzed by next-generation sequencing (NGS) panel. The pathogenicity of germline mutations was categorized based on American College of Medical Genetics and Genomics (ACMG) guidelines. Results: In total, 3 (0.67%) patients (diagnosed as bladder cancer, schwannoma, and medulloblastoma) were identified harboring truncating pathogenic (P)/likely pathogenic (LP) germline mutations in the RNase III domain. The remaining 445 (99.33%) patients carried 447 uncertain significance (VUS) mutations, of which 416 (92%) were missense mutations lied in different domains and 52% (234/450) located in exon 20-23. The median age was 60 years old with an age range from 0 to 90. The higher frequency cancer type contained lung cancer (35.9%), glioma (10.0%), liver cancer (8.4%). In addition, the two highest frequencies of DICER1 missense variants were c.3334A > G (p. Asn1112Asp, n = 58) and c.3227G > A (p. Ser1076Asn, n = 53), which lied in unknown functional domain of the protein and had been reported in Clinvar. Their clinical significance and pathogenicity remain further study. Conclusions: In our study, DICER1 germline mutations mostly occurred in exon 20-23 and 92% were missense mutations. We reported 3 new cases of tumors associated with DICER1 syndrome, which expanded the DICER1-related tumor spectrum. Understanding the clinical significance of germline DICER1 VUS could improve the identification of potentially high-risk variants. Reclassifying these variants could make them useful for predictive, prognostic, and preventive purposes in clinical practice.

DICER1-associated hepatic cystic neoplasm with pleuropulmonary blastoma-like features: a novel clinicopathologic diagnosis

This report documents a unique multicystic neoplasm of the liver in an 8-month-old boy with a heterozygous germline pathogenic DICER1 variant. This neoplasm, initially considered most likely a mesenchymal hamartoma based on imaging, demonstrated the characteristic histologic pattern of embryonal rhabdomyosarcoma residing in the subepithelial or cambium layer-like zone of the epithelial-lined cysts. Thus, although the differential diagnosis includes mesenchymal hamartoma, a young child with a multicystic mass lesion in the liver, lung, or kidney should both raise the possibility of a germline pathogenic DICER1 variant and also not be mistaken for one of the other hepatic neoplasms of childhood.

Complete Tracheal Ring Deformity, Recurrent Pneumothoraces and Pleuropulmonary Blastoma in a Child: Coincidence or Common Genetic Cause?

Complete tracheal ring deformity (CTRD) is a rare abnormality of unknown etiology characterized by circumferentially continuous cartilaginous tracheal rings leading to variable degrees of tracheal stenosis with or without additional heart and lung malformations. Pleuropulmonary blastomas (PPB) are rare malignant mesenchymal tumors, which occur almost exclusively in young children. Pathogenic germline DICER1 variants are associated with PPB but also with other tumors like rhabdomyosarcoma or syndromic diseases like GLOW (Global developmental delay, lung cysts, overgrowth and Wilms tumor) syndrome. Here, we report a case with CTRD and recurrent pneumothoraces who additionally developed PPB on the genetic background of a pathogenic DICER1 variant.

Phenotypic similarities within the morphologic spectrum of DICER1-associated sarcomas and pleuropulmonary blastoma: Histopathologic features guide diagnosis in the LMIC setting.

Extrapulmonary DICER1-associated sarcomas (DS) can harbor morphological features overlapping with pleuropulmonary blastoma. We report three children with intracranial and genital tract sarcomas, suspected to have DS based on a heterogeneous yet defining combination of spindle-cell sarcomatous and blastemal morphology, with rhabdomyomatous differentiation. Foci of immature cartilage at diagnosis (n=2/3) and increased neuroepithelial differentiation at recurrence (n=1) were noted. Morphological suspicion prompted somatic testing at reference centers, confirming likely biallelic, loss-of-function, and "hotspot" missense DICER1 variants in all three tumors. This can serve as a model for this diagnosis in resource-limited settings and has implications for germline testing, surveillance, and tumor management.

Pediatric cystic nephroma: clinical and molecular genetic characteristics

Cystic nephroma (CN) is a rare renal tumor occurring in children which belongs to a group of neoplasms linked with the inherited DICER1 syndrome. Given the rarity of CNs, it is important to describe clinical, radiological, and molecular genetic characteristics of these tumors in children and adolescents as well as to analyze treatment outcomes. We present our experience in managing 8 patients with histologically verified CN who received treatment and consultations at the D. Rogachev NMRCPHOI over a period of 9 years (2012–2020). The study was approved by the Independent Ethics Committee and the Scientific Council of the D. Rogachev NMRCPHOI. The patients’ parents gave their consent to the use of their child’s data, including photographs, for research purposes and in publications. We performed a retrospective analysis of clinical presentation, radiological findings, the extent of treatment given to patients, treatment outcomes, and the results of molecular genetic testing. The study included patients aged between 8.6 and 197 months at diagnosis (the median age was 14.2 months). The analysis of initial complaints revealed that six patients (75%) had an increased abdominal girth and a palpable mass in the abdomen, one patient (12.5%) presented with arterial hypertension, and another patient (12.5%) had a mass detected by a routine abdominal ultrasound examination. On contrast-enhanced computed tomography scans, CNs appeared as multicystic masses with thin, contrast-enhancing septa; the CN volume ranged from 59.7 to 1293.1 cm3 (the median volume was 626.3 cm3 ). In all cases, the diagnosis of CN was verified histologically. Surgical treatment included nephrectomy (n = 6) or partial resection of the affected kidney (n = 2) with the removal of the tumor. Some patients (n = 5) included in our analysis received pre-operative chemotherapy at the discretion of their treating physicians. Molecular genetic testing was carried out for 7 children: 4 out of 7 patients (57.1%) were found to have somatic and germline mutations in the DICER1 gene. Carriers of pathogenic DICER1 variant were identified in the family of 1 patient. The median duration of follow-up was 17.6 months (range: 1.7 to 58.9 months). Currently, all patients are alive, no relapses have occurred. Cystic renal neoplasms detected by radiological investigations should be reviewed at the reference centers for pediatric oncological diseases and included CN in the differential diagnosis. Initial surgery is the first line of treatment for cystic nephroma. The final diagnosis is made on the basis of a histological examination of tumor tissue. All patients with confirmed CN should be referred for genetic counseling and molecular genetic testing for germline mutations in the DICER1 gene and should receive surveillance recommendations for the early detection of other metachronous DICER1-associated tumors.

Likely foregut endoderm origin for a postzygotic mutation affecting the RNase IIIb domain of DICER1

In 2016, we reported a child with bilateral lung cysts and left lung type II pleuropulmonary blastoma (PPB), classic phenotypes of DICER1 syndrome; we identified a DICER1 hotspot mutation c.5425G>A,...

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

BACKGROUNDMolecular characterization in pediatric papillary thyroid cancer (PTC), distinct from adult PTC, is important for developing molecularly targeted therapies for progressive radioiodine-refractory (131I-refractory) PTC.METHODSPTC samples from 106 pediatric patients (age range: 4.3-19.8 years; n = 84 girls, n = 22 boys) who were admitted to SNUH (January 1983-March 2020) were available for genomic profiling. Previous transcriptomic data from 125 adult PTC samples were used for comparison.RESULTSWe identified genetic drivers in 80 tumors: 31 with fusion oncogenes (RET in 21 patients, ALK in 6 patients, and NTRK1/3 in 4 patients); 47 with point mutations (BRAFV600E in 41 patients, TERTC228T in 2 patients [1 of whom had a coexisting BRAFV600E], and DICER1 variants in 5 patients); and 2 with amplifications. Fusion oncogene PTCs, which are predominantly detected in younger patients, were at a more advanced stage and showed more recurrent or persistent disease compared with BRAFV600E PTCs, which are detected mostly in adolescents. Pediatric fusion PTCs (in patients <10 years of age) had lower expression of thyroid differentiation genes, including SLC5A5, than did adult fusion PTCs. Two girls with progressive 131I-refractory lung metastases harboring a TPR-NTRK1 or CCDC6-RET fusion oncogene received fusion-targeted therapy; larotrectinib and selpercatinib decreased the size of the tumor and restored 125I radioiodine uptake. The girl with the CCDC6-RET fusion oncogene received 131I therapy combined with selpercatinib, resulting in a tumor response. In vitro 125I uptake and 131I clonogenic assays showed that larotrectinib inhibited tumor growth and restored radioiodine avidity.CONCLUSIONSIn pediatric patients with fusion oncogene PTC who have 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 patients with PTC.FUNDINGThe Ministry of Science, ICT and Future Planning (NRF-2016R1A2B4012417 and 2019R1A2C2084332); the Korean Ministry of Health and Welfare (H14C1277); the Ministry of Education (2020R1A6A1A03047972); and the SNUH Research Fund (04-2015-0830).TRIAL REGISTRATIONTwo patients received fusion-targeted therapy with larotrectinib (NCT02576431; NAVIGATE) or selpercatinib (LOXO-RET-18018).

Prevalence of Pathogenic Germline DICER1 Variants in Young Individuals Thyroidectomised Due to Goitre - A National Danish Cohort.

IntroductionDICER1 syndrome encompasses a variety of benign and malignant manifestations including multinodular goitre, which is the most common manifestation among individuals carrying pathogenic DICER1 variants. This is the first study estimating the prevalence of pathogenic DICER1 variants in young individuals with multinodular goitre.MethodsDanish individuals diagnosed with nodular goitre based on thyroidectomy samples in 2001-2016 with the age limit at time of operation being ≤ 25 years were offered germline DICER1 gene testing.ResultsSix of 46 individuals, 13% (CI [3.3;22.7], p <0.05), diagnosed with nodular goitre on the basis of thyroidectomy samples under the age of 25 years had pathogenic germline variants in DICER1. They were found in different pathoanatomical nodular goitre cohorts i.e. nodular goitre (n=2), colloid nodular goitre (n=3) and hyperplastic nodular goitre (n=1).ConclusionsWe recommend referral of patients thyroidectomised due to goitre aged <21 years and patients thyroidectomised due to goitre aged <25 years with a family history of goitre to genetic counselling. Patients of all ages thyroidectomised due to goitre, who are affected by another DICER1 manifestation should be referred to genetic counselling.

Unusual phenotypes in patients with a pathogenic germline variant in DICER1.

Pathogenic germline DICER1 variants are associated with pleuropulmonary blastoma, multinodular goiter, embryonal rhabdomyosarcoma and other tumour types, while mosaic missense DICER1 variants in the RNase IIIb domain are linked to cause GLOW (global developmental delay, lung cysts, overgrowth, and Wilms' tumor) syndrome. Here, we report four families with germline DICER1 pathogenic variants in which one member in each family had a more complex phenotype, including skeletal findings, facial dysmorphism and developmental abnormalities. The developmental features occur with a variable expressivity and incomplete penetrance as also described for the neoplastic and dysplastic lesions associated with DICER1 variants. Whole exome sequencing (WES) was performed on all four cases and revealed no further pathogenic or likely pathogenic dominant, homozygous or compound heterozygous variants in three of them. Notably, a frameshift variant in ARID1B was detected in one patient explaining part of her phenotype. This series of patients shows that pathogenic DICER1 variants may be associated with a broader phenotypic spectrum than initially assumed, including predisposition to different tumours, skeletal findings, dysmorphism and developmental abnormalities, but genetic work up in syndromic patients should be comprehensive in order not to miss additional underlying /modifying causes.

DICER1-Mutated Botryoid Fibroepithelial Polyp of the Parotid Duct: Report of the First Case

DICER1, a member of the ribonuclease III family, is involved in the biogenesis of microRNAs and, hence, it influences gene expression regulation. DICER1 germline (associated with the inherited DICER1 syndrome) or somatic mutations have been linked to tumorigenesis in histogenetically diverse benign and malignant neoplasms in different organs including pleuropulmonary blastoma, cystic nephroma, embryonal rhabdomyosarcoma, nasal chondromesenchymal hamartoma, poorly differentiated thyroid carcinoma, thyroblastoma, intracranial sarcoma and gonadal Sertoli-Leydig cell tumors in addition to others. Moreover, rare botryoid (giant) fibroepithelial polyps may harbor this mutation. Herein, we describe the first reported case of a DICER1-mutated botryoid fibroepithelial polyp occurring within the parotid duct of a 65-year-old female who has no other features or family history of the DICER1 syndrome. Based on its distinctive morphology, we tested this lesion specifically for DICER1 mutations and confirmed the presence of a pathogenic DICER1 variant with a low allele frequency, consistent with a somatic mutation.

Programmed Death Ligand 1 Expression and Related Markers in Pleuropulmonary Blastoma.

Pleuropulmonary blastoma (PPB), a rare childhood neoplasm of the lung, is linked to pathogenic DICER1 variants. We investigated checkpoint inhibitor markers including Programmed Death Ligand 1 (PD-L1), PD1, CD8 and tumor mutational burden (TMB) in PPB. Cases were collected from departmental archives and the International PPB/DICER1 Registry. Immunohistochemistry (IHC) for PD-L1, PD-1, CD8 and DNA mismatch repair (MMR) genes were performed. In addition, normal-tumor paired whole exome sequencing (WES) was performed in two cases. Twenty-five PPB cases were studied, consisting of Type I (n = 8, including 2 Ir), Type II (n = 8) and Type III (n = 9). PD-L1 combined positive score (CPS) of 1, 4 and 80 was seen in three (3/25, 12.0%) cases of Type II PPB with negative staining in the remaining cases. PD-1 and CD8 stains demonstrated positive correlation (P < .05). The density of PD1 and CD8 in the interface area was higher than within tumor (P < .05). The MMR proteins were retained. TMB was 0.65 mutations/Mb in type II PPB with high expression of PD-L1, and 0.94 mutations/Mb in one negative PD-L1 case with metastatic tumor. A small subpopulation of PPB patient might benefit from checkpoint immunotherapy due to positive PD-L1 staining.

Evaluating the Effect of 3'-UTR Variants in DICER1 and DROSHA on Their Tissue-Specific Expression by miRNA Target Prediction.

Untranslated gene regions (UTRs) play an important role in controlling gene expression. 3′-UTRs are primarily targeted by microRNA (miRNA) molecules that form complex gene regulatory networks. Cancer genomes are replete with non-coding mutations, many of which are connected to changes in tumor gene expression that accompany the development of cancer and are associated with resistance to therapy. Therefore, variants that occurred in 3′-UTR under cancer progression should be analysed to predict their phenotypic effect on gene expression, e.g., by evaluating their impact on miRNA target sites. Here, we analyze 3′-UTR variants in DICER1 and DROSHA genes in the context of myelodysplastic syndrome (MDS) development. The key features of this analysis include an assessment of both “canonical” and “non-canonical” types of mRNA-miRNA binding and tissue-specific profiling of miRNA interactions with wild-type and mutated genes. As a result, we obtained a list of DICER1 and DROSHA variants likely altering the miRNA sites and, therefore, potentially leading to the observed tissue-specific gene downregulation. All identified variants have low population frequency consistent with their potential association with pathology progression.

Prevalence and Spectrum of DICER1Mutations in Adult-Onset Thyroid Nodules

Abstract Context: DICER1 mutations are found in multinodular goiter and differentiated thyroid carcinoma in children, and can be a manifestation of DICER1 syndrome, but the prevalence of DICER1 mutations and their significance in adult-onset thyroid nodules is unknown. Objective: Determine 1) the prevalence of DICER1 hotspot mutations in thyroid nodules; 2) the frequency of a second DICER1 pathogenic variant in thyroid nodules with DICER1 hotspot mutations; 3) the prevalence of other thyroid cancer driver mutations in thyroid nodules with and without DICER1 hotspot mutations. Design: Population-based study of 14,993 consecutive fine needle aspiration biopsies of thyroid nodules evaluated by ThyroSeq v3. From 214 DICER1 hotspot-positive cases, we selected 61, matched to DICER1 hotspot-negative nodules. We performed full sequencing of all exons and exon-intron boundaries of DICER1. Setting: Commercial and university-based laboratories in the United States and Canada Results: Among 14,993 thyroid nodules, 214 (1.4%) revealed a DICER1 hotspot mutation. A second pathogenic/likely pathogenic variant in DICER1 was found in 45/59 (76%) DICER1 hotspot-positive nodules studied while no other DICER1 variant was identified in the DICER1 hotspot-negative group by full DICER1 sequencing. Other alterations in thyroid-related genes were significantly more frequent in DICER1 hotspot-negative nodules (32/61) than in DICER1 hotspot-positive nodules (4/59) (p&amp;lt;0.0001). Conclusions: DICER1 alterations occur in a proportion of adult thyroid nodules and appear mutually exclusive with alterations in other thyroid cancer-related genes. DICER1 hotspot mutations occur with a second hit in most cases and could suggest occult DICER1 syndrome in adults with thyroid nodules.

Identification of a Novel DICER1 Germline Mutation in Thyroid Follicular Adenoma Using Whole Exome Sequencing

Backgrounds: DICER1 protein is a member of the ribonuclease III family of proteins that cleaves non-coding small RNA precursors to generate mature miRNAs, which in turn regulate gene expression post-transcriptionally. Thyroid abnormalities are frequently observed in DICER1 syndrome with multinodular goiter present in families in which a germline DICER1 mutation is segregating. Recently, we identified a germline DICER1 mutation in a family with multiple tumors using whole exome sequencing (WES). Methods and Materials: Following informed consent, WES of peripheral blood DNA was carried out on affected individual. Sanger sequencing was performed to confirm the DICER1 variant detected by WES and to assess her family for mutation in the same DICER1 exon (exon 20). Results: An 8 year-old girl presented with abdominal mass. Laparoscopic radical nephrectomy was done due to Wilms tumor. At age 12, palpable mass on the right thyroid lobe was found, and right hemithyroidectomy was performed. She was diagnosed with follicular adenoma, and she started to take levothyroxine. At age 13, palpable thyroid mass on the left thyroid lobe was identified, and total thyroidectomy was performed due to progressively enlarged remnant thyroid gland with multiple nodules. The pathological result was adenomatous goiter with a cystic change. During the evaluation, a 1.5cm follicular cyst in the left ovary, 0.7cm cystic lesion in the right middle lobe of the lung, and air-trappings in both lungs were observed. We performed WES which revealed a novel heterozygous missense mutation, c.3506C>G(p.S1169*) in exon 20 of the DICER1 gene. During the follow-up, she showed a severely enlarged right kidney with multiple septated cysts. Right total nephrectomy was done due to hemorrhage progression in cysts and biopsy revealed cystic nephroma. Continuous renal replacement therapy was applied after right nephrectomy, and maintenance hemodialysis was applied. Conclusions: We identified a novel DICER1 germline mutation in a family with thyroid follicular adenoma, Wilms tumor, and contralateral progressive cystic nephroma which is the first report in Korea.

DICER1 Syndrome and Cancer Predisposition: From a Rare Pediatric Tumor to Lifetime Risk.

DICER1 syndrome is a rare genetic condition predisposing to hereditary cancer and caused by variants in the DICER1 gene. The risk to present a neoplasm before the age of 10 years is 5.3 and 31.5% before the age of 60. DICER1 variants have been associated with a syndrome involving familial pleuropulmonary blastoma (PPB), a rare malignant tumor of the lung, which occurs primarily in children under the age of 6 years and represents the most common life-threatening manifestation of DICER1 syndrome. Type I, II, III, and Ir (type I regressed) PPB are reported with a 5-year overall survival ranging from 53 to 100% (for type Ir). DICER1 gene should be screened in all patients with PPB and considered in other tumors mainly in thyroid neoplasms (multinodular goiter, thyroid cancer, adenomas), ovarian tumors (Sertoli-Leydig cell tumor, sarcoma, and gynandroblastoma), and cystic nephroma. A prompt identification of this syndrome is necessary to plan a correct follow-up and screening during lifetime.

Childhood Rhabdomyosarcoma of the Female Genital Tract: Association with Pathogenic DICER1 Variation, Clinicopathological Features, and Outcomes

Rhabdomyosarcomas (RMS) of the female genital tract (FGT) have been recently found to be associated with germline pathogenic variation in DICER1, which can underlie a tumor-predisposition disorder. We sought to determine the incidence of pathogenic variation in DICER1 in a cohort of RMSs of FGT, as well as to evaluate the clinicopathological features and outcomes of the patients. We retrospectively reviewed medical records of the patients diagnosed with RMS of the FGT between 1990-2019. Molecular genetic sequencing of the tumor to detect an RNase IIIb domain hotspot mutation in DICER1 samples was performed in seven patients. Individuals with a missense mutation in the tumor were also screened for a loss of function germline mutation in DICER1. Of 210 cases of pediatric RMS, 11 arose from the FGT. Molecular genetic sequencing of the tumor samples revealed a somatic missense mutation in the RNase IIIb domain of DICER1 in a total of three patients, two patients with embryonal RMS (ERMS) of cervix/uterus and one patient with ovarian ERMS. As a result of genetic testing for the loss of function germline mutation in DICER1, a heterozygous pathogenic variant was also found in two of these patients. Despite the limited number of patients, our findings suggest that it is important to be aware of the possible association between RMS of FGT and pathogenic germline DICER1 variants since the detection of this mutation in a patient or relatives can provide the opportunity for surveillance of related conditions that may improve long-term outcomes and survival.

Prevalence and Spectrum of DICER1 Mutations in Adult-onset Thyroid Nodules with Indeterminate Cytology.

DICER1 mutations are found in multinodular goiter and differentiated thyroid carcinoma in children, and can be a manifestation of DICER1 syndrome, but the prevalence of DICER1 mutations and their significance in adult-onset thyroid nodules is unknown. Determine (1) the prevalence of DICER1 hotspot mutations in thyroid nodules; (2) the frequency of a second DICER1 pathogenic variant in thyroid nodules with DICER1 hotspot mutations; (3) the prevalence of other thyroid cancer driver mutations in thyroid nodules with and without DICER1 hotspot mutations. Population-based study of 14 993 consecutive fine needle aspiration biopsies of thyroid nodules evaluated by ThyroSeq v3. From 214 DICER1 hotspot-positive cases, we selected 61, matched to DICER1 hotspot-negative nodules. We performed full sequencing of all exons and exon-intron boundaries of DICER1. Commercial and university-based laboratories in the United States and Canada. Among 14 993 thyroid nodules, 214 (1.4%) revealed a DICER1 hotspot mutation. A second pathogenic/likely pathogenic variant in DICER1 was found in 45/59 (76%) DICER1 hotspot-positive nodules studied while no other DICER1 variant was identified in the DICER1 hotspot-negative group by full DICER1 sequencing. Other alterations in thyroid-related genes were significantly more frequent in DICER1 hotspot-negative nodules (32/61) than in DICER1 hotspot--positive nodules (4/59) (P < .0001). DICER1 alterations occur in a proportion of adult thyroid nodules and appear mutually exclusive with alterations in other thyroid cancer-related genes. DICER1 hotspot mutations occur with a second hit in most cases and could suggest occult DICER1 syndrome in adults with thyroid nodules.

Hematologic indices in individuals with pathogenic germline DICER1 variants.

Pathogenic germline variants in DICER1 underlie an autosomal dominant, pleiotropic tumor-predisposition disorder. Murine models with the loss of DICER1 in hematopoietic stem cell progenitors demonstrate hematologic aberrations that include reductions in red and white blood cell counts, hemoglobin volume, and impaired maturation resulting in dysplasia. We investigated whether hematologic abnormalities such as those observed in DICER1-deficient mice were observed in humans with a pathogenic germline variant in DICER1. A natural history study of individuals with germline pathogenic DICER1 variants and family controls conducted through the National Cancer Institute (NCI) evaluated enrollees at the National Institutes of Health Clinical Center during a comprehensive clinical outpatient visit that included collecting routine clinical laboratory studies. These were compared against normative laboratory values and compared between the DICER1 carriers and controls. There were no statistical differences in routine clinical hematology laboratory studies observed in DICER1 carriers and family controls. A review of the medical history of DICER1 carriers showed that none of the individuals in the NCI cohort developed myelodysplastic syndrome or leukemia. Query of the International Pleuropulmonary Blastoma/DICER1 Registry revealed 1 DICER1 carrier who developed a secondary leukemia after treatment of pleuropulmonary blastoma. We found limited evidence that the hematologic abnormalities observed in murine DICER1 models developed in our cohort of DICER1 carriers. In addition, no cases of myelodysplastic syndrome were observed in either the NCI cohort or the International Pleuropulmonary Blastoma/DICER1 Registry; 1 case of presumed secondary leukemia was reported. Abnormalities in hematologic indices should not be solely attributed to DICER1. This trial was registered at www.clinicaltrials.gov as #NCT01247597.