Germline DICER1 Mutations Research Articles

Somatic DICER1-Mutant Benign Thyroid Nodules in Adults: A Group of Follicular Nodular Disease With Continuous Growth.

Germline DICER1 mutations cause familial multinodular goiter (MNG). However, the prevalence of somatic DICER1 mutations in non-MNG benign thyroid nodules and their characteristics remain unknown. Adult-onset thyroid nodules with a pathological diagnosis were genotyped via targeted sequencing. DICER1-mutant nodules were assessed clinically and pathologically. Organoids were established to investigate follicular formation and growth. Transcriptomic analysis was conducted to evaluate transcriptional features, which were validated by immunofluorescence. Among 931 adult-onset thyroid nodules, we identified 13 benign thyroid nodules with DICER1 hotspot mutations. The majority harbored a somatic DICER1 hotspot mutation with a somatic DICER1 truncating variant. Clinically, 38.5% of the DICER1-mutant nodules exhibited substantial growth. DICER1-mutant nodules with durations longer than 2 years were substantially enlarged (P=.0448). Pathologically, all DICER1-mutant nodules were defined as thyroid follicular nodular disease (TFND). The TFND nodules with DICER1 mutations grew faster than those with wild-type DICER1. Organoid culture of a DICER1-mutant nodule revealed increased active follicular formation. Compared with the normal thyroid tissues, the DICER1-mutant nodules had comparable thyroid differentiation scores, significantly higher ERK scores (P=.0141) and lower epithelial‒mesenchymal transition scores (P=.0001). Moreover, the expression of genes related to follicular polarity, such as CDH16, SLC5A5, TSHR and TPO, was downregulated in the DICER1-mutant nodules. Somatic DICER1 two-hit mutations represent a notable percentage in adult TFND patients, and DICER1-mutant benign thyroid nodules were characterized by continuous growth.

DICER-1 Mutation Associated Sarcoma of Thyroid in An Adult Male

Abstract Introduction/Objective DICER-1 is an autosomal dominant tumor predisposition syndrome caused by germline DICER1 mutations. In the thyroid, it is associated with an early-onset multinodular goiter (MNG) and low-grade thyroid carcinomas. The aggressive variants thyroblastoma and poorly differentiated carcinoma are however seen in the pediatric age group. We report a case of DICER-1-associated (rhabdomyo) sarcoma without primitive components in an adult male. Methods/Case Report A 44-year-old healthy male with a family history of MNG, presented with a large left neck mass confirmed on imaging with largest 6.4cm, and extension into the mediastinum. FNA showed a malignant spindle cell- rich neoplasm with negative expression for Keratins, TTF-1, PAX-8, Calcitonin, INSM- 1 and SOX-10. The CEA and calcitonin were normal. The lymphoma was excluded by flow cytometry. The patient underwent a left thyroidectomy with central and left selective neck dissection. On gross examination, the left lobe of the thyroid was replaced by a tan- white, partially encapsulated solid mass. Microscopic examination revealed nests and sheets of ovoid to spindle- shaped cells with eosinophilic cytoplasm in fascicles with hypocellular areas with loose stroma. Foci of rhabdomyoblastic differentiation with straps cells, positive for desmin and myogenin were identified. Brisk mitotic activity and tumor necrosis were present. No primitive thyroid epithelium or blastemal component was identified. Tumor cells were negative for S100, SOX10 CD34, CD31, SMA, calponin, CD99, NKX2.2, SS18-SSX which excluded malignant peripheral nerve sheath tumor, angiosarcoma, leiomyosarcoma, Ewing’s sarcoma, and synovial sarcoma. Next-generation sequencing showed a DICER1 c.4517G>A (p.W1506) and c.5437G>C (p.E1813Q) mutation, both variants reported as germ-line variants. A final diagnosis of DICER-1-associated rhabdomyosarcoma was rendered. The patient underwent rehabilitation at another facility and lost to follow-up. Results (if a Case Study enter NA) NA Conclusion The case highlights the expanding spectrum of DICER-1-associated malignant tumors and the importance of keeping it in the differential diagnosis of unusual malignant tumors of the thyroid even in adults.

DICER1 Mutations Enable Rare Tumor Formation

Abstract Introduction/Objective DICER1 is a tumor suppressor gene that imparts a slight increase in tumor formation when mutated. The protein plays a role in processing miRNA that silences transcription. Germline mutations of DICER1 predispose to tumors in a known set of organs and rarely in other locations. However the presence of additional genetic aberrations further increases the likelihood of tumor formation. Acting as a compounding factor, DICER1 mutations can present a constantly shifting cancer phenotype of affected patients. Of particular interest here is the development of both Pineoblastoma and Malignant spindle cell sarcoma in a young patient. Sarcomas are estimated to make up only 10% of pediatric cancers and Pineal masses only 3%. Methods/Case Report This case involves an 8 year old male with a history of Pineoblastoma who originally presented with slowly worsening ataxia. A screening ultrasound on following visits identified an abdominal mass that was confirmed with computed tomography. Subsequent biopsies showed malignant spindle cells arranged in a herringbone pattern. Additionally these cells displayed high mitotic activity and hyperchromatic nuclei. Surprisingly, they also demonstrated extramedullary hematopoiesis. Multiple stains were performed however no significant conclusion could be made. The appearance of this tumor and its rarity prompted a request for a Complete Comprehensive Sarcoma Panel via Next Generation Sequencing. This confirmed the presence of pathologic BRAF and DICER1 genes. From that the diagnosis of DICER1 associated Malignant Spindle Cell Sarcoma was made. BRAF V600E is the most common genetic variant and is seen in multiple cancers but only seen in 1-3% of sarcomas. Pathologic variants of the DICER1 gene exist on exons 13 and 25. The presence of these exon mutations in some way affect DICER1 protein function and compound the effects of the mutated BRAF gene. This situation is unique as such neoplasms are rarely found in the anterior abdominal wall and showcases the effects of DICER1 on rare tumor phenotypes. Results (if a Case Study enter NA) NA Conclusion Continuing research into both DICER1 protein pathways is essential for isolating a diagnosis and guiding treatment. It would seem screening images and genetic testing would benefit pediatric or even adult patients with common and rare cancers. Extra effort made toward this would not be outside the norm as personalized medicine is gradually becoming the standard for cancer treatment.

Abstract 135: Resolving the tumorigenesis continuum of DICER1 syndrome with novel lineage-trackable genetically engineered mouse model

Abstract Background: DICER1 syndrome is a rare cancer predisposition syndrome associated with germline DICER1 mutations, which develops pulmonary or extra-pulmonary manifestations mostly in pediatric patients. Unlike classic tumor suppressors, the 2nd hit in DICER1 gene is a missense mutation that renders the RNase IIIb domain defective; therefore, this mutant form of DICER1 is the only protein expressed in these cancer cells, leading to a biased 5p-miRNA production deficiency. Many DICER1 cancers are sarcomas; we therefore postulate the cell of origin is mesenchymal. We recently developed a RNase IIIb-mutant mouse strain and embryonic activation of this mutant along with silencing of the other Dicer1 allele in Mullerian mesenchymal progenitor cells led to the development of tumors resembling sarcomas in human patients. To expand the model and enable lineage tracking, we developed a tamoxifen inducible, tdTomato-trackable, Hypermethylated in Cancer 1 (HIC1)-creERT2 driven transgenic mouse strain. Hic1 marks mesenchymal progenitors. With this strain, we created a model that histologically recapitulates the 3 renal tumors in DICER1 syndrome: cystic nephromas, Wilms tumors, and anaplastic sarcomas. Objective: to identify oncogenic events underlying Dicer1 mutation-driven murine kidney tumor development with single cell RNA-sequencing (scRNA-seq). Method: To build the tumorigenesis continuum, we harvested kidneys from Dicer1+/fl-D1693N and Dicer1fl/fl-D1693N mice at 1, 3, 6, months post tamoxifen injection, sorted out tdTomato+/CD45-/Epcam- cells, and performed scRNA-seq. Five endpoint tumors were included for analyses. Single cell transcriptomic profiles were integrated and clustered using Seurat to identify cell populations that emerge and expand along the tumor development continuum. Differential gene expression, pathway analysis were conducted to identify genes/oncogenic pathways that are activated along the course of tumor development. Cell differentiation trajectory analysis will be performed using Monocle. Results: Integration of 5 tumors revealed diverse cell populations: epithelial, mesenchymal, endothelial cells, lymphocytes, and macrophages. We further clustered the mesenchymal population and identified sub-populations such as highly proliferative cells, muscle satellite cells, and terminally differentiated muscle cells. These mesenchymal cells show high expression of blastema markers (Ncam1, Sox11) - a histological component in Wilms tumors. Temporal trajectory of tumorigenesis with time point samples is currently being analyzed. Conclusion: With scRNA-seq, we begin to unravel heterogeneity of these murine tumors and will identify critical oncogenic events driving the development of DICER1 syndrome-associated cancer, enabling us to utilize this model to develop therapeutic approaches to improve patient management. Citation Format: Joyce Zhang, Shary Chen, Yana Moscovitz, Branden Lynch, Maxwell Douglas, Janine Senz, Wilder Scott, Michael Underhill, Yemin Wang, David Huntsman. Resolving the tumorigenesis continuum of DICER1 syndrome with novel lineage-trackable genetically engineered mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 135.

Expanding Our Knowledge of DICER1 Gene Alterations and Their Role in Thyroid Diseases.

Mutations in DICER1, a gene involved in RNA interference, have been associated with a wide range of multi-organ neoplastic and non-neoplastic conditions. Historically known for its association with pleuropulmonary blastoma, DICER1 syndrome has received more attention due to the association with newly discovered diseases and tumors. Recent studies evaluating DICER1 mutations and DICER1-driven thyroid disease in both pediatric and adult thyroid nodules revealed thyroid disease as the most common manifestation of DICER1 mutations. This study undertakes a comprehensive investigation into DICER1 mutations, focusing on their role in thyroid diseases. Specific attention was given to thyroid follicular nodular disease and differentiated thyroid carcinomas in infancy as highly indicative of germline DICER1 mutation or DICER1 syndrome. Additionally, poorly differentiated thyroid carcinoma and thyroblastoma were identified as potential indicators of somatic DICER1 mutations. Recognizing these manifestations should prompt clinicians to expedite genetic evaluation for this neoplastic syndrome and classify these patients as high risk for additional multi-organ malignancies. This study comprehensively synthesizes the current knowledge surrounding this genetically associated entity, providing intricate details on histologic findings to facilitate its diagnosis.

Pediatric Sertoli-Leydig Cell Tumors of the Ovary: An Integrated Study of Clinicopathological Features, Pan-cancer-Targeted Next-generation Sequencing and Chromosomal Microarray Analysis From a Single Institution.

Sertoli-Leydig cell tumors (SLCTs) are currently classified into 3 molecular subtypes: DICER1 -mutant (younger patient age), FOXL2 -mutant, and DICER1/FOXL2 -wildtype. However, it is not clear whether all pediatric SLCTs are DICER1 -mutant molecular subtypes and whether other molecular genetic aberrations besides DICER1 are involved in the pathogenesis and prognosis of these tumors. We studied comprehensive data for 8 cases of pediatric SLCTs, including clinicopathological features, pan-cancer-targeted next-generation sequencing/OncoKids panel, and chromosomal microarray analysis, to further analyze the correlation among clinicopathological features, molecular genetic aberrations, and prognosis. The ages of the patients ranged from 4 to 16 years (median, 14y). Seven cases were moderately differentiated, and one was poorly differentiated with heterologous mesenchymal elements. Two cases had heterologous epithelium or retiform elements. Follow-up was available for all 8 patients (median, 49.5mo). Seven patients were alive without evidence of recurrence or metastasis, and only case 5 developed metastases (synchronous bilateral pulmonary tumors with rhabdomyosarcomatous differentiation). All 8 tumors were found to harbor somatic hotspot DICER1 mutations, and 5 patients carried germline DICER1 mutations (2 of them had the phenotype of DICER1 syndrome). Together with recent studies, the DICER1 mutation frequency is 100% in pediatric SLCTs (n=27, age≤16y). Copy number alterations were detected in 3 tumors; the only recurrent copy number alterations was the gain of whole chromosome 6 in case 5 and case 8. This is the first report describing clinicopathological features and molecular alterations in pediatric SLCTs. Our results demonstrate that all pediatric SLCTs belong to the DICER1 -mutant molecular subtype, highlighting that somatic hotspot DICER1 mutation detection has high sensitivity (100%) for the auxiliary diagnosis of pediatric SLCTs (age ≤16y). Some pediatric SLCTs harbor molecular genetic aberrations other than DICER1 mutation, and their significance needs further study.

Congenital pleuropulmonary blastoma in a newborn with a variant of uncertain significance in DICER1 evaluated by RNA-sequencing

BackgroundPleuropulmonary blastoma (PPB) is a rare mesenchymal malignancy of the lung and is the most common pulmonary malignancy in infants and children. Cystic PPB, the earliest form of PPB occurring from birth to approximately two years of age, is often mistaken for a congenital pulmonary airway malformation, as the two entities can be difficult to distinguish on imaging and pathology. Diagnosis of PPB should prompt workup for DICER1 syndrome, an autosomal dominant tumor predisposition syndrome. We report a newborn with a congenital PPB presenting with tachypnea and hypoxia, who was found to have variant of uncertain clinical significance (VUS) in DICER1.Case presentationA term female infant developed respiratory distress shortly after birth. Initial imaging was concerning for a congenital pulmonary airway malformation versus congenital diaphragmatic hernia, and she was transferred to a quaternary neonatal intensive care unit for management and workup. Chest CT angiography demonstrated a macrocytic multicystic lesion within the right lower lobe without systemic arterial supply. The pediatric surgery team was consulted, and the neonate underwent right lower lobectomy. Pathology revealed a type I PPB. Oncology and genetics consultants recommended observation without chemotherapy and single gene sequencing of DICER1, which identified a germline VUS in DICER1 predicted to alter splicing. RNA-sequencing from blood demonstrated that the variant resulted in an in-frame deletion of 29 amino acids in a majority of transcripts from the affected allele. Due to the patient’s young age at presentation and high clinical suspicion for DICER1 syndrome, tumor surveillance was initiated. Renal and pelvic ultrasonography were unremarkable.ConclusionWe present the case of a term neonate with respiratory distress and cystic lung mass, found to have a type I PPB with a germline VUS in DICER1 that likely increased her risk of DICER1-related tumors. Nearly 70% of patients with PPB demonstrate germline mutations in DICER1. Review of RNA sequencing data demonstrates the difficulty in classifying splice variants such as this. Penetrance is low, and many patients with pathogenic DICER1 variants do not develop a malignancy. Best practice surgical and oncologic recommendations include an individualized approach and tumor board discussion. This case highlights the importance of a multidisciplinary team approach and the utility of international registries for patients with rare diagnoses.

Challenges in DICER1-Associated Lung Disease

Pleuropulmonary blastoma (PPB) is a tumor occurring almost exclusively in infants and young children. This is the most common primary-lung malignancy in childhood. There is age-associated progression through a distinctive sequence of pathologic changes, from a purely multicystic lesion type I to a high-grade sarcoma type II and III. While complete resection is the cornerstone treatment for type I PPB, aggressive chemotherapy with a less favorable prognosis is associated with type II and III. DICER1 germline mutation is positive in 70% of children with PPB. Diagnosis is challenging, as it resembles congenital pulmonary airway malformation (CPAM) in imaging. Although PPB is an extremely rare malignancy, over the past five years we have encountered several children diagnosed with PPB in our medical center. Herein, we present some of these children and discuss diagnostic, ethical, and therapeutic challenges.

Ultrasound features of multinodular goiter in DICER1 syndrome

DICER1 syndrome is caused by germline pathogenic mutations in the DICER1 gene. Multinodular goiter (MNG) is a common clinical feature of DICER1 syndrome in children and adults. The aim of this study was to determine the ultrasound (US) characteristics of MNG in patients with DICER1 syndrome. This retrospective study evaluated thyroid US in patients with DICER1 germline mutations (DICER1mut+) performed between 2011 and 2018 at a single center by the same pediatric endocrinologist, and the images were re-examined by an independent pediatric radiologist from another academic center. Patients < 18 years with DICER1mut+ and DICER1mut+ parents without previous thyroidectomy were included. Ultrasound phenotypes of MNG in the setting of DICER1 mutations were compared with known US features of thyroid malignancy. Thirteen DICER1mut+ patients were identified (10 children, 3 adults). Three children had a normal thyroid US; therefore, thyroid abnormalities were assessed in seven children and three adults. In both children and adults, multiple (≥ 3) mixed (cystic/solid) nodules predominated with single cystic, single cystic septated and single solid nodules, occasionally with a “spoke-like” presentation. All solid lesions were isoechogenic, and in only one with multiple solid nodules, intranodular blood flow on power/color Doppler was observed. Remarkably, macrocalcifications were present in all three adults. The spectrum of ultrasonographic findings of MNG in DICER1mut+ patients is characteristic and largely distinct from typical features of thyroid malignancy and therefore should inform physicians performing thyroid US of the possible presence of underlying DICER1 syndrome.

A systematic review of the clinicopathological features and prognostic outcomes of DICER1-mutant malignant brain neoplasms.

DICER1-mutant malignant brain neoplasms are very rare tumors, and published data have relied on case reports or small case series. In this review, the authors aimed to systematically summarize the types and distribution patterns of DICER1 mutations, clinicopathological characteristics, and prognostic outcomes of these tumors. The authors searched PubMed and Web of Science for relevant studies. They included studies if they provided individual patient data of primary malignant brain tumors carrying DICER1 mutations. The authors found 16 studies consisting of 9 embryonal tumors with multilayered rosettes (ETMRs), 30 pineoblastomas, 52 primary intracranial sarcomas, and 27 pituitary blastomas. Pineoblastoma, ETMR, and pituitary blastoma were more likely to carry DICER1 germline mutations, while only a small subset of primary intracranial sarcomas harbored these mutations (p < 0.001). Nearly 80% of tumors with germline mutations also had another somatic mutation in DICER1. ETMR and primary intracranial sarcoma were associated with an increased risk for tumor progression and relapse compared with pituitary blastoma and pineoblastoma (p = 0.0025), but overall survival (OS) was not significantly different. Gross-total resection (GTR) and radiotherapy administration were associated with prolonged OS. ETMR, pineoblastoma, primary intracranial sarcoma, and pituitary blastoma should be considered rare phenotypes of the DICER1 syndrome, and families should be counseled and screened for associated tumors. ETMR and primary intracranial sarcoma had a higher risk of relapse. GTR and radiotherapy appeared to improve the OS of patients with DICER1-mutant malignant intracranial 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.

DICER1-associated Tumors in the Female Genital Tract: Molecular Basis, Clinicopathologic Features, and Differential Diagnosis.

DICER1 syndrome is a tumor predisposition syndrome in which patients are at an increased risk of developing a wide variety of benign and malignant neoplasms with a hallmark constellation of pediatric pleuropulmonary blastoma, cystic nephroma, and thyroid lesions. DICER1 encodes an RNA endoribonuclease that is crucial to the processing of microRNA and may play a role in the maturation of Müllerian tissue. Within the gynecologic tract, germline mutations in DICER1 are associated with an array of rare tumors, including Sertoli-Leydig cell tumor, embryonal rhabdomyosarcoma of the cervix, gynandroblastoma, and juvenile granulosa cell tumor, which typically present in childhood, adolescence, or early adulthood. In addition, somatic DICER1 mutations have been described in rare gynecologic tumors such as adenosarcoma, Sertoli cell tumor, ovarian fibrosarcoma, cervical primitive neuroectodermal tumor, carcinosarcoma, and germ cell tumors. In light of the significant association with multiple neoplasms, genetic counseling should be considered for patients who present with a personal or family history of these rare DICER1-associated gynecologic tumors. This review highlights the most current understanding of DICER1 genetic alterations and describes the clinical, histopathologic, and immunohistochemical features and differential diagnoses for gynecologic tumors associated with DICER1 mutation.

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 &gt; G (p. Asn1112Asp, n = 58) and c.3227G &gt; 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.

Proceedings of the North American Society of Head and Neck Pathology, Los Angeles, CA, March 20, 2022: DICER1-Related Thyroid Tumors.

DICER1 syndrome is an autosomal dominant tumor predisposition syndrome caused by germline DICER1 mutations. In the thyroid, DICER1 syndrome is associated with early-onset multinodular goiter and thyroid carcinomas. Subsequent studies have shown that somatic DICER1 mutations, though rare, can occur in follicular-patterned thyroid tumors, such as follicular adenomas and follicular thyroid carcinomas, with a higher rate seen in pediatric follicular thyroid carcinomas and in follicular thyroid carcinomas with a macrofollicular architecture. Somatic DICER1 mutations have also been reported in pediatric papillary thyroid carcinomas lacking other alterations typically associated with thyroid tumorigenesis. Although thyroid carcinomas with underlying DICER1 mutations are usually indolent, recent studies have shown that pediatric poorly differentiated thyroid carcinoma and thyroblastoma, both aggressive tumors, also harbor DICER1 mutations. This review will discuss mechanisms of DICER1 tumorigenesis and describe thyroid tumors associated with germline and somatic DICER1 mutations.

Expanding the spectrum of thyroid carcinoma with somatic DICER1 mutation: a survey of 829 thyroid carcinomas using MSK-IMPACT next-generation sequencing platform.

DICER1 gene encodes an RNaseIII endoribonuclease essential for the cleavage of pre-microRNA to mature microRNA. Germline DICER1 mutation results in DICER syndrome, a cancer predisposition syndrome which manifests in the thyroid gland as early-onset multinodular goiter and increased risk for differentiated thyroid carcinoma. Recently, somatic DICER1 mutations were described in various thyroid neoplasms, including follicular adenoma, papillary thyroid carcinoma, follicular carcinoma, and poorly differentiated thyroid carcinoma. In this study, we identified and described 14 cases (1.7%) with somatic DICER1 mutations from a cohort of 829 patients with thyroid follicular cell-derived thyroid carcinomas which were sequenced using MSK-IMPACT targeted next-generation sequencing platform. We expanded the histologic spectrum of thyroid carcinomas with somatic DICER1 mutations to include Hurthle cell carcinoma, high-grade differentiated thyroid carcinoma, and anaplastic thyroid carcinoma. All patients were adults with a median age of diagnosis of 59years (range: 22-82). Although rare, a subset of thyroid cancers, including the aggressive subtypes, display somatic DICER1 mutations, some of which have oncogenic potential.

Macrofollicular variant follicular thyroid tumors are DICER1 mutated and exhibit distinct histological features.

DICER1 germline mutations cause DICER1 syndrome, in which multinodular goitre is a common feature. Recently, somatic DICER1 mutations have been reported in sporadic thyroid carcinomas, of which the newly described macrofollicular variant of follicular thyroid carcinoma (MV-FTC) seems particularly enriched for this aberrancy. We report here histological and genetic findings in five follicular thyroid tumours with macrofollicular architecture (four carcinomas and one adenoma). We have diagnosed five cases during a year-long period at the Karolinska University Hospital, a tertiary thyroid cancer center with a catchment area of approximately 2.3 million inhabitants. Tumour DNA was interrogated using a commercially available massive parallel sequencing platform. All cases were female patients, ranging from 13 to 33years at surgery. A single patient was a DICER1 syndrome carrier; the others were sporadic cases. All tumours displayed a macrofollicular architecture with a broad capsule. The MV-FTCs displayed capsular invasion, but never vascular invasion. Areas with degenerative changes (microinfarctions) were noted in all cases, and focal papillary growth was observed in the majority. The Ki-67 proliferation index was always above 4%. All cases displayed DICER1 gene mutations, of which four of five cases displayed RNase IIIb hot-spot missense mutations adjoined by a second, deleterious variant in three of five tumouurs. Macrofollicular variants of follicular thyroid tumours are predominantly found in younger females and are strongly linked to somatic DICER1 gene mutations. Histological features such as a broad tumorous capsule, focal infarctions and areas with papillae could constitute clues prompting further genetic analyses.

Nasal Chondromesenchymal Hamartoma in a Patient With DICER1-Predisposition Syndrome

Abstracts Nasal chondromesenchymal hamartomas (CMHs) are extremely rare tumors that are sometimes seen in patients with germline DICER1 mutations. These patients are also at increased risk of pleuropulmonary blastomas, as well as other uncommon tumors. We present the case of an 8-year-old girl with a history of pleuropulmonary blastoma who presented with worsening nasal obstruction and clinical symptoms of sinusitis secondary to a nasal CMH. The diagnosis of nasal CMH is discussed, as well as DICER1 syndrome.

Relationship between DICER1 mutations and immunotherapy biomarkers in solid tumors.

2603 Background: Dicer1 functions as a tumor suppressor in mouse models. In humans, somatic mutations are associated with many cancers in adults, and patients with DICER1 syndrome with DICER1 germline mutations are susceptible to childhood cancers. DICER1 is the core caner-intrinsic CTL-evasion gene, especially positive correlate with innate anti-PD-1 resistance signature or IPRES signature and hERV expression which involved in sensitivity and resistance to ICIs. Nevertheless, the association between mutations in DICER1 and the Chinese patients, the relationship between DICER1 mutations with immunotherapy biomarkers are unknown. Methods: NGS and clinical data were collected from 10953 Western pan-cancer patients (TCGA cohort). A 539-gene panel targeted sequencing assay was performed on FFPE tumor samples from 3514 Chinese pan-cancer patients (Chinese cohort). Both DICER1 mutation ratio and TMB were calculated on the two cohorts following the same criteria.DNA NGS testing (MSI-high vs low/stable (MSS)) in Chinese cohort were included. NGS data of 3514 patients who also detected PD-L1 expression from Chinese clinical dataset were analyzed to explore the association with mutation and PD-L1. The survival information was collected from 1661 pan-cancer patients to analyze the association between DICER1 mutation and efficacy of immunotherapy (MSKCC cohort). Results: In total, 2.91% (319/10953) patients in TCGA harbored DICER1 mutation; in the Chinese cohort, the DICER1 mutation ratio (2.67%, 94/3514) was similar to TCGA. The top 5 mutant DICER1-associated cancer types in Chinese cohort were lung cancer, colon adenocarcinoma, liver cancer, uterine corpus endometrial carcinoma, melanoma. In both cohorts, TMB level of mutation group was significantly higher than wild-type group (p &lt; 0.001). The ration of mutation group in MSI-H (50%) and MSI-L (23.53%) was significantly higher than wild-type group in Chinese cohort (2.17%) (p &lt; 0.001). In addition, the ratio of PD-L1 positive expression (≥1%) in mutation group (48.94%, 46/48) was significantly higher than wild-type in Chinese cohort (38.48%,1316/2104) (p &lt; 0.05). The survival probability of mutation group was significantly longer than wild-type group in immunotherapy. Conclusions: The results indicated that DICER1 mutation was associated with a higher TMB, MSI-H and PD-L1 expression level in Chinese patients. Patients with DICER1 mutations may benefit more from ICIs.

Multimodality Imaging of Pleuropulmonary Blastoma: Pearls, Pitfalls, and Differential Diagnosis

Pleuropulmonary blastomas are rare, potentially aggressive embryonal cancers of the lung parenchyma and pleural surfaces that account for 0.25%-0.5% of primary pulmonary malignancies in children. Pleuropulmonary blastomas are classified as cystic (type I), mixed cystic and solid (type II), and solid (type III). Pleuropulmonary blastoma occurs in the same age group (0-6 years) as other more common solid tumors such as neuroblastoma and Wilms tumor. Differential diagnosis includes metastasis from Wilms tumor and macrocystic congenital pulmonary airway malformation (CPAM). A key pathologic and genetic discriminator is the DICER1 germline mutation found in patients with pleuropulmonary blastoma. Imaging, histopathologic, and clinical data are important to use in conjunction in order to determine the diagnosis and risk stratification of pleuropulmonary blastomas. Survival varies from poor to good, depending on type. However, the spectrum of pleuropulmonary blastoma is insufficiently understood due to the variable presentation of this rare disease. We present a current review of the literature regarding pleuropulmonary blastomas in this article.

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.