Temporal order of RNase IIIb and loss-of-function mutations during development determines phenotype in pleuropulmonary blastoma / DICER1 syndrome: a unique variant of the two-hit tumor suppression model

Identification of Homozygous Somatic DICER1 Mutation in Pleuropulmonary Blastoma

Pleuropulmonary blastoma (PPB) is a rare, progressive, and aggressive malignant intrathoracic tumor observed during childhood. Mutations in the DICER1 gene have been considered a major etiologic factor of PPB and cause a variety of tumor types in children and young adults. We present a 3-year-old boy with type II PPB. Multimodal treatment consisting of surgery and neoadjuvant chemotherapy was effective. DICER1 mutations were examined by Sanger sequencing, microarray comparative genomic hybridization, and microsatellite markers. The results revealed that a somatic biallelic DICER1 mutation with uniparental disomy was present in the tumor tissue.

DICER1-Related Embryonal Rhabdomyosarcoma of the Uterine Corpus in a Prepubertal Girl

BACKGROUND

Germline DICER1 mutations increase the risk of developing a wide variety of generally uncommon tumors. We describe a case of DICER1-related embryonal rhabdomyosarcoma (ERMS) of the uterine corpus in a prepubertal girl.

CASE

A 10-year-old- girl with a history of cystic nephroma presented with a 3-week history of vaginal bleeding. A 3-cm mass filling the uterine cavity was detected, and histopathologic examination of hysteroscopy-guided biopsy samples revealed ERMS. Molecular genetic sequencing of the tumor sample revealed a DICER1 mutation.

SUMMARY AND CONCLUSION

This report highlights the importance of screening for DICER1 mutations in the presence of the early-onset features of this syndrome, and extends the spectrum of DICER1-related tumors by showing the mutation in a case of ERMS of the uterine corpus.

Secondary Sarcomas: Biology, Presentation, and Clinical Care

Secondary sarcomas are a subset of sarcomas that occur in patients with prior cancer diagnoses and are associated with environmental or genetic factors. Although secondary sarcomas are rare in general, there are predisposing factors that can substantially increase this risk in certain populations. Herein, we review the environmental factors with the strongest association of sarcoma risk, including chemical exposure, certain viruses, cytotoxic and immunosuppressive agents, chronic edema, and radiation exposure. Additionally, the most common genetic disorders that carry a predisposition for sarcoma development will be discussed, including hereditary retinoblastoma (RB), Li-Fraumeni syndrome (LFS), neurofibromatosis type 1 (NF1), and DICER1 syndrome. Although treatment does not generally differ for sporadic versus secondary sarcomas, awareness of the risk factors can alter therapeutic strategies to minimize risk, aid prompt diagnosis by increasing clinical suspicion, and allow for appropriate surveillance and genetic counseling for those patients with cancer predisposition syndromes.

Presacral malignant teratoid neoplasm in association with pathogenic DICER1 variation

We report two malignant sacrococcygeal tumors in infants that were associated with pathogenic DICER1 variation. These tumors were composed of primitive neuroepithelium, embryonal rhabdomyosarcoma, and cartilage and initially diagnosed as immature teratomas. One child developed intracranial metastasis and died. The second child underwent surgery and chemotherapy and achieved complete remission. This child subsequently developed five additional DICER1-associated neoplasms by age nine. Genetic analysis revealed that both tumors harbored biallelic pathogenic DICER1 variation. We believe these cases represent another novel subtype of DICER1-associated tumor. This new entity, which we propose to call DICER1-associated presacral malignant teratoid neoplasm, may be difficult initially to distinguish from immature teratoma, but recognizing it as an entity can prompt appropriate classification as an aggressive malignancy and facilitate appropriate genetic counseling, DICER1 germline variant testing, screening, and education.

Multinodular goitre is a gateway for molecular testing of DICER1 syndrome

BACKGROUND

DICER1 syndrome is an autosomal dominant disorder that predisposes individuals to develop benign or malignant tumours from infancy to adulthood. There is low-to-moderate penetrance of tumour development, which is sex- and age-dependent. Multinodular goitre (MNG) is among the most highly penetrant phenotype of the disorder, especially in females.

PATIENTS AND METHODS

We report a series of eight families referred for childhood-onset of MNG or DICER1-related tumours with familial history of MNG in relatives. No additional families with these criteria stated were identified during the same date. We screened DNA samples from the probands and members of their family (40) for constitutional DICER1 variants using Next Generation Sequencing tools.

RESULTS

Germline pathogenic DICER1 gene variants were identified in all probands and several of their relatives: 64% presented with MNG/thyroidectomy as the phenotypic expression of the syndrome. DICER1 gene variants were identified in the RNAseIII and the PAZ domains. All tumour tissues studied presented clonal pathogenic variants in hotspot regions. Early identification of DICER1 variant carriers has permitted diagnosis and therapeutic scheme correction for two patients and cascade testing in relatives.

CONCLUSIONS

Multinodular goitre is uncommon in children. Childhood-onset MNG, multiple occurrences of the disease within the same family, or its association with rare benign or malignant tumours should raise suspicions of anomalies in the DICER1 gene, as proposed by recent international recommendations. Early detection of DICER1 pathogenic variants has important consequences in terms of therapeutic strategy, early tumour screening, and genetic counselling.

[DICER1 constitutional pathogenic variant syndrome: Where are we in 2019?]

Inactivating germline pathogenic variants of the DICER1 gene are responsible for a spectrum of rare diseases, which expanded a lot in recent years. The constitution of an U.S. registry with these patients and their families as well as the registration of patients in European databases of rare tumors helped to better identify diseases encountered in this syndrome but also to study its pathophysiology (major role in miRNA maturation and recently discovered functions, e.g. in genome integrity maintenance). Most encountered disorders are pediatric malignancies, mainly the pulmonary pneumoblastoma and Sertoli-Leydig tumours. However, benign pathologies such as thyroid goiters, cystic nephromas or pulmonary cystic lesions are also frequently reported. Homogeneous guidelines regimens written by the European groups working on very rare pediatric tumors are proposed but it is important to underscore that they rely on rare scientific data; therefore overall consensus remains precarious. The genetic counseling to families is still difficult due to the large observed spectrum of tumors and the incomplete penetrance. In this article, the authors update current knowledge on the DICER1 syndrome.

Imaging of DICER1 syndrome

DICER1 syndrome is a highly pleiotropic tumor predisposition syndrome that has been increasingly recognized in the last 10 years. Diseases in the syndrome result from mutations in both copies of the gene DICER1, a highly conserved gene that is critically implicated in micro-ribonucleic acid (miRNA) biogenesis and hence modulation of messenger RNAs. In general, susceptible individuals carry an inherited germline mutation that disables one copy of DICER1; within tumors, a very characteristic second mutation alters function of the other gene copy. About 20 hamartomatous, hyperplastic or neoplastic conditions comprise DICER1 syndrome. Most are not life-threatening, but some are aggressive malignancies. There are many unaffected carriers because penetrance is generally low; however, clinically occult thyroid nodules and lung cysts are frequent. Rare diseases of early childhood were the first recognized conditions in DICER1 syndrome, while other conditions affect adolescents and adults. The hallmarks of DICER1 syndrome are certain rare tumors including pleuropulmonary blastoma; cystic nephroma; ovarian Sertoli-Leydig cell tumor; sarcomas of the cervix, kidneys and cerebrum; pituitary blastoma; ciliary body medulloepithelioma; and nasal chondromesenchymal hamartoma. Radiologists are often the first practitioners to observe these diverse manifestations and play a primary role in recognizing DICER1 syndrome.

Dental abnormalities in individuals with pathogenic germline variation in DICER1

Pathogenic germline variation in the microRNA processing gene DICER1 gives rise to an autosomal dominant, tumor-predisposition disorder. Conditional deletion of Dicer1 in murine dental epithelium shows that it controls tooth patterning, size, number, and shape. The human dental phenotype of people with germline pathogenic variation in DICER1 is unknown. DICER1-carriers (n = 57) and family controls (n = 55) were evaluated at the NIH Clinical Center dental clinic as part of a comprehensive medical evaluation. Digital panoramic radiographs, bite-wing radiographs, and oral photographs were collected. A single observer, blind to DICER1 status, reviewed the dental records and determined the presence or absence of 11 dental characteristics as described in the clinic notes, radiographs, or oral photographs. Subjective phenotypes were reviewed on radiographs by two examiners (blind to DICER1 status) for the presence or absence of the dental characteristics to reduce inconsistencies. By simple association, bulbous crown, periodontitis, and taurodontism were all significant (p < .05). Logistic regression with chi-square maximum likelihood estimates showed that bulbous crown and periodontitis remained significant. Recognition of these phenotypes may aid identification of individuals and families at risk for DICER1-associated neoplasms. These findings may also guide dental care for individuals with germline DICER1 pathogenic variation.

Successful treatment of metastatic cerebral recurrence of pleuropulmonary blastoma

Pleuropulmonary blastoma (PPB) is a rare pediatric tumor. The central nervous system (CNS) is the most common site of extrathoracic metastasis. The prognosis of PPB patients with CNS metastases is dismal: most patients die within one year after recurrence. Here, we describe two patients diagnosed with PPB who developed intracranial recurrences shortly after the end of their initial treatment and were successfully treated by gross total resection, radiotherapy, and chemotherapy. Both patients are in complete remission four and three years after recurrence. Although an optimal regimen remains to be determined, these cases demonstrate that PPB with CNS metastases is potentially curable.

DICER1 Mutations in the Era of Expanding Integrative Clinical Sequencing in Pediatric Oncology

PURPOSE

DICER1 syndrome is a recently described inherited cancer predisposition syndrome caused by pathogenic variants in DICER1. With the recent increase in integrative clinical sequencing for pediatric patients with cancer, our understanding of the DICER1 syndrome continues to evolve, as new and rare pathogenic variants are reported. As the frequency of integrative clinical sequencing increases, discussions regarding challenges encountered in the interpretation of sequencing results are essential to continue to advance the field of cancer predisposition. The purpose of this work was to identify patients with somatic and/or germline DICER1 variants in our patient population and to discuss sequencing interpretation and the clinical recommendations that result from the integrative clinical sequencing results.

METHODS

Patients were enrolled in the PEDS-MIONCOSEQ study. This integrative clinical sequencing study includes paired tumor/normal whole-exome sequencing and tumor transcriptome sequencing. Patients identified as having DICER1 variants were included.

RESULTS

We report a DICER1 variant of unknown clinical significance in a patient with a highly unusual response to therapy. Two patients had diagnoses clarified once the integrative clinical sequencing revealing a DICER1 variant was available. We also discovered a patient with low-level DICER1 mosaicism and the challenges encountered in the sequencing interpretation for this patient. In addition to the sequencing data and result interpretation, this work also highlights testing and screening recommendations made to patients with DICER1 variants and their families on the basis of these results.

CONCLUSION

This work serves to extend the DICER1 phenotype and advance the utility of clinical integrative sequencing in the fields of pediatric oncology and cancer genetic predisposition.

Neoplasm Risk Among Individuals With a Pathogenic Germline Variant in DICER1

PURPOSE

DICER1 syndrome is an autosomal-dominant, pleiotropic tumor-predisposition disorder caused by pathogenic germline variants in DICER1. We sought to quantify risk, hazard rates, and the probability of neoplasm incidence accounting for competing risks ("cumulative incidence") of neoplasms (benign and malignant) and standardized incidence ratios for malignant tumors in individuals with DICER1 pathogenic variation.

PATIENTS AND METHODS

We combined data from three large cohorts of patients who carry germline pathogenic variation in DICER1. To reduce ascertainment bias, we distinguished probands from nonprobands. Neoplasm diagnoses were confirmed by review of pathology reports and/or central review of surgical pathology materials. Standardized cancer incidence ratios were determined relative to the SEER program, which does not capture all DICER1-associated neoplasms. For all malignancies and benign tumors ("neoplasms," excluding type Ir pleuropulmonary blastoma and thyroid nodules), we used the Kaplan-Meier method and nonparametric cumulative incidence curves to estimate neoplasm-free survival.

RESULTS

We calculated the age at first neoplasm diagnosis (systematically ascertained cancers plus DICER1-associated neoplasms pleuropulmonary blastoma, cystic nephroma, and nasal chondromesenchymal hamartoma) in 102 female and male nonproband DICER1 carriers. By age 10 years, 5.3% (95% CI, 0.6% to 9.7%) of nonproband DICER1 carriers had developed a neoplasm (females, 4.0%; males, 6.6%). By age 50 years, 19.3% (95% CI, 8.4% to 29.0%) of nonprobands had developed a neoplasm (females, 26.5%; males, 10.2%). After age 10 years, female risk was elevated compared with male risk. Standardized cancer incidence ratio analysis of 102 nonproband DICER1 carriers, which represented 3,344 person-years of observation, showed significant cancer excesses overall, particularly of gynecologic and thyroid cancers.

CONCLUSION

This work provides the first quantitative analysis of site-specific neoplasm risk and excess malignancy risk in 102 systematically characterized nonproband DICER1 carriers. Our findings inform DICER1 syndrome phenotype, natural history, and genetic counseling.

The prevalence of germline DICER1 pathogenic variation in cancer populations

BACKGROUND

The DICER1 syndrome is an autosomal dominant tumor-predisposition disorder associated with pleuropulmonary blastoma, a rare pediatric lung cancer. Somatic missense variation in "hotspot" codons in the RNaseIIIb domain (E1705, D1709, G1809, D1810, E1813) is observed in DICER1-associated tumors. Previously, we found the prevalence of germline pathogenic DICER1 variation in the general population is 1:10,600. In this study, we investigated the prevalence of pathogenic DICER1 germline variation in The Cancer Genome Atlas (TCGA; 32 adult cancer types; 9,173 exomes) and the Therapeutically Applicable Research to Generate Effective Treatment (TARGET; two pediatric cancer types; 175 exomes) cohorts.

METHODS

All datasets were annotated and binned into four categories: pathogenic, likely pathogenic, variant of unknown significance, or likely benign.

RESULTS

The prevalence of DICER1 pathogenic variants was 1:4,600 in TCGA. A single participant with a uterine corpus endometrial carcinoma harbored two pathogenic germline DICER1 (hotspot and splice-donor) variants, and a single participant with a rectal adenocarcinoma harbored a germline DICER1 stop-gained variant. In the smaller TARGET dataset, we observed no pathogenic germline variants.

CONCLUSION

This is the largest comprehensive analysis of DICER1 pathogenic variation in adult and pediatric cancer populations using publicly available data. The observation of germline DICER1 variation with uterine corpus endometrial carcinoma merits additional investigation.

Germline and mosaic mutations causing pituitary tumours: genetic and molecular aspects

While 95% of pituitary adenomas arise sporadically without a known inheritable predisposing mutation, in about 5% of the cases they can arise in a familial setting, either isolated (familial isolated pituitary adenoma or FIPA) or as part of a syndrome. FIPA is caused, in 15-30% of all kindreds, by inactivating mutations in the AIP gene, encoding a co-chaperone with a vast array of interacting partners and causing most commonly growth hormone excess. While the mechanisms linking AIP with pituitary tumorigenesis have not been fully understood, they are likely to involve several pathways, including the cAMP-dependent protein kinase A pathway via defective G inhibitory protein signalling or altered interaction with phosphodiesterases. The cAMP pathway is also affected by other conditions predisposing to pituitary tumours, including X-linked acrogigantism caused by duplications of the GPR101 gene, encoding an orphan G stimulatory protein-coupled receptor. Activating mosaic mutations in the GNAS gene, coding for the Gα stimulatory protein, cause McCune-Albright syndrome, while inactivating mutations in the regulatory type 1α subunit of protein kinase A represent the most frequent genetic cause of Carney complex, a syndromic condition with multi-organ manifestations also involving the pituitary gland. In this review, we discuss the genetic and molecular aspects of isolated and syndromic familial pituitary adenomas due to germline or mosaic mutations, including those secondary to AIP and GPR101 mutations, multiple endocrine neoplasia type 1 and 4, Carney complex, McCune-Albright syndrome, DICER1 syndrome and mutations in the SDHx genes underlying the association of familial paragangliomas and phaeochromocytomas with pituitary adenomas.

Novel intronic DICER1 variation associated with pleuropulmonary blastoma in two siblings

Pleuropulmonary blastomas (PPB) are rare aggressive paediatric lung malignancies associated with DICER1 variants. We present two cases, a 2-year-old girl with upper respiratory tract symptoms as well as a 6-month-old girl sibling undergoing screening due to family history of malignancy. Imaging of the 2-year-old girl revealed a large mass filling the right hemithorax which was determined to be a type II PPB after pathological examination. Imaging of the 6-month-old sibling demonstrated a small cystic lesion in the posterior basal segment of the right lower lobe which was determined to be a type 1r PPB after pathological examination. The 2-year-old girl received adjuvant chemotherapy while the baby sister underwent resection alone and both are alive and well at 12 months and 7 months, respectively. Sequence analysis in both cases confirmed the same DICER1 variation, c.2437-2A>G (likely pathogenic), which has not been previously described in the literature.

Structural renal abnormalities in the DICER1 syndrome: a family-based cohort study

BACKGROUND

The DICER1 syndrome is a tumor-predisposition disorder caused by germline pathogenic variation in DICER1 and is associated with cystic nephroma and other renal neoplasms. Dicer1 mouse and rare human DICER1 syndrome case reports describe structural kidney and collecting system anomalies. We investigated renal function and the frequency of structural abnormalities of the kidney and collecting system in individuals with germline loss-of-function variants in DICER1.

METHODS

In this family-based cohort study, prospectively ascertained germline DICER1-mutation carriers (DICER1-carriers) and unaffected family controls were evaluated at the National Institutes of Health Clinical Center with renal ultrasound and comprehensive laboratory testing. Two radiologists reviewed the imaging studies from all participants for structural abnormalities, cysts, and tumors.

RESULTS

Eighty-nine DICER1-carriers and 61 family controls were studied. Renal cysts were detected in 1/33 DICER1-carrier children without history of cystic nephroma. Similar proportions of adult DICER1-carriers (8/48; 17%) and controls (11/50; 22%) had ultrasound-detected renal cysts (P = 0.504). 8/89 (9%) DICER1-carriers harbored ultrasound-detected structural abnormalities of varying severity within the collecting system or kidney, nephrolithiasis, or nephrocalcinosis. None of the family controls (0/61) had similar findings on ultrasound (P = 0.02). No meaningful differences in renal laboratory values between DICER1-carriers and unaffected family controls were observed.

CONCLUSIONS

Our report is the first to systematically characterize renal function and anatomy in a large prospective cohort of DICER1-carriers and DICER1-negative family controls. DICER1-carriers may be at increased risk of structural anomalies of the kidney or collecting system. The role for DICER1 in renal morphogenesis merits additional investigation.

DICER1 mutation and pituitary prolactinoma

A young woman carrying germline DICER1 mutation was discovered to have a pituitary microprolactinoma when she became amenorrhoic. The mutation was identified as a result of family screening following the early death of the patient’s daughter with ovarian cancer. The patient was in follow-up screening for thyroid disease, and investigations were initiated when she became amenorrhoic. MR scan revealed a 6 mm diameter pituitary microadenoma and raised prolactin. The prolactin was efficiently suppressed with low-dose cabergoline, and her menstrual cycles resumed. Dicer is an RNase enzyme, which is essential for processing small non-coding RNAs. These molecules play pleiotropic roles in regulating gene expression, by targeting mRNA sequences for degradation. DICER1 plays different roles depending on cell context, but is thought to be a functional tumour suppressor gene. Accordingly, germline mutation in one DICER1 allele is insufficient for oncogenesis, and a second hit on the other allele is required, as a result of postnatal somatic mutation. Loss of DICER1 is linked to multiple tumours, with prominent endocrine representation. Multinodular goitre is frequent, with increased risk of differentiated thyroid cancer. Rare, developmental pituitary tumours are reported, including pituitary blastoma, but not reports of functional pituitary adenomas. As DICER1 mutations are rare, case reports are the only means to identify new manifestations and to inform appropriate screening protocols.

DICER1 Syndrome: DICER1 Mutations in Rare Cancers

DICER1 syndrome is a rare genetic disorder that predisposes individuals to multiple cancer types. Through mutations of the gene encoding the endoribonuclease, Dicer, DICER1 syndrome disrupts the biogenesis and processing of miRNAs with subsequent disruption in control of gene expression. Since the first description of DICER1 syndrome, case reports have documented novel germline mutations of the DICER1 gene in patients with cancers as well as second site mutations that alter the function of the Dicer protein expressed. Here, we present a review of mutations in the DICER1 gene, the respective protein sequence changes, and clinical manifestations of DICER1 syndrome. Directions for future research are discussed.

PTEN, DICER1, FH, and Their Associated Tumor Susceptibility Syndromes: Clinical Features, Genetics, and Surveillance Recommendations in Childhood

PTEN hamartoma tumor syndrome (PHTS), DICER1 syndrome, and hereditary leiomyomatosis and renal cell cancer (HLRCC) syndrome are pleiotropic tumor predisposition syndromes that include benign and malignant neoplasms affecting adults and children. PHTS includes several disorders with shared and distinct clinical features. These are associated with elevated lifetime risk of breast, thyroid, endometrial, colorectal, and renal cancers as well as melanoma. Thyroid cancer represents the predominant cancer risk under age 20 years. DICER1 syndrome includes risk for pleuropulmonary blastoma, cystic nephroma, ovarian sex cord-stromal tumors, and multinodular goiter and thyroid carcinoma as well as brain tumors including pineoblastoma and pituitary blastoma. Individuals with HLRCC may develop multiple cutaneous and uterine leiomyomas, and they have an elevated risk of renal cell carcinoma. For each of these syndromes, a summary of the key syndromic features is provided, the underlying genetic events are discussed, and specific screening is recommended. Clin Cancer Res; 23(12); e76-e82. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

Familial multinodular goiter and Sertoli-Leydig cell tumors associated with a large intragenic in-frame DICER1 deletion

OBJECTIVE

Familial multinodular goiter (MNG), with or without ovarian Sertoli-Leydig cell tumor (SLCT), has been linked to DICER1 syndrome. We aimed to search for the presence of a germline DICER1 mutation in a large family with a remarkable history of MNG and SLCT, and to further explore the relevance of the identified mutation.

DESIGN AND METHODS

Sanger sequencing, Fluidigm Access Array and multiplex ligation-dependent probe amplification (MLPA) techniques were used to screen for DICER1 mutations in germline DNA from 16 family members. Where available, tumor DNA was also studied. mRNA and protein extracted from carriers' lymphocytes were used to characterize the expression of the mutant DICER1.

RESULTS

Nine of 16 tested individuals carried a germline, in-frame DICER1 deletion (c.4207-41_5364+1034del), which resulted in the loss of exons 23 and 24 from the cDNA. The mutant transcript does not undergo nonsense-mediated decay and the protein is devoid of specific metal ion-binding amino acids (p.E1705 and p.D1709) in the RNase IIIb domain. In addition, characteristic somatic 'second hit' mutations in this region were found on the other allele in tumors.

CONCLUSIONS

Patients with DICER1 syndrome usually present a combination of a typically truncating germline DICER1 mutation and a tumor-specific hotspot missense mutation within the sequence encoding the RNase IIIb domain. The in-frame deletion found in this family suggests that the germline absence of p.E1705 and p.D1709, which are crucial for RNase IIIb activity, may be enough to permit DICER1 syndrome to occur.

DICER1 and Associated Conditions: Identification of At-risk Individuals and Recommended Surveillance Strategies

Pathogenic germline DICER1 variants cause a hereditary cancer predisposition syndrome with a variety of manifestations. In addition to conferring increased cancer risks for pleuropulmonary blastoma (PPB) and ovarian sex cord-stromal tumors, particularly Sertoli-Leydig cell tumor, individuals with pathogenic germline DICER1 variants may also develop lung cysts, cystic nephroma, renal sarcoma and Wilms tumor, nodular hyperplasia of the thyroid, nasal chondromesenchymal hamartoma, ciliary body medulloepithelioma, genitourinary embryonal rhabdomyosarcoma, and brain tumors including pineoblastoma and pituitary blastoma. In May 2016, the International PPB Registry convened the inaugural International DICER1 Symposium to develop consensus testing and surveillance and treatment recommendations. Attendees from North America, Europe, and Russia provided expert representation from the disciplines of pediatric oncology, endocrinology, genetics, genetic counseling, radiology, pediatric surgery, pathology, and clinical research. Recommendations are provided for genetic testing; prenatal management; and surveillance for DICER1-associated pulmonary, renal, gynecologic, thyroid, ophthalmologic, otolaryngologic, and central nervous system tumors and gastrointestinal polyps. Risk for most DICER1-associated neoplasms is highest in early childhood and decreases in adulthood. Individual and caregiver education and judicious imaging-based surveillance are the primary recommended approaches. These testing and surveillance recommendations reflect a consensus of expert opinion and current literature. As DICER1 research expands, guidelines for screening and treatment will continue to be updated. Clin Cancer Res; 24(10); 2251-61. ©2018 AACR.

A pair of DICER1-positive monozygotic twins: One with pleuropulmonary blastoma, another with acute transient hepatitis

Pleuropulmonary blastoma (PPB) is the most common primary malignant neoplasm of the lung in children that is associated with a germline mutation in DICER1. In this report, we share an interesting case of a pair of monozygotic twins: one of them developed PPB when she was 4-year old, while the other developed acute transient hepatitis when she was 5-year old. Next-Gen sequencing for DICER1 mutations of their family revealed that both twins and their mother had c.C3675A mutation. The mother also had a history of multinodular goiter. Identification of DICER1 mutation carriers and close surveillance of individuals at risk for DICER1 syndrome may allow early detection and hence better outcome.

The prevalence of DICER1 pathogenic variation in population databases

The DICER1 syndrome is associated with a variety of rare benign and malignant tumors, including pleuropulmonary blastoma (PPB), cystic nephroma (CN) and Sertoli-Leydig cell tumor (SLCT). The prevalence and penetrance of pathogenic DICER1 variation in the general population is unknown. We examined three publicly-available germline whole exome sequence datasets: Exome Aggregation Consortium (ExAC), 1,000 Genomes (1,000 G) and the Exome Sequencing Project (ESP). To avoid over-estimation of pathogenic DICER1 variation from cancer-associated exomes, we excluded The Cancer Genome Atlas (TCGA) variants from ExAC. All datasets were annotated with snpEff and ANNOVAR and variants were classified into four categories: likely benign (LB), unknown significance (VUS), likely pathogenic (LP), or pathogenic (P). The prevalence of DICER1 P/LP variants was 1:870 to 1:2,529 in ExAC-nonTCGA (53,105 exomes) estimated by metaSVM and REVEL/CADD, respectively. A more stringent prevalence calculation considering only loss-of-function and previously-published pathogenic variants detected in ExAC-nonTCGA, yielded a prevalence of 1:10,600. Despite the rarity of most DICER1 syndrome tumors, pathogenic DICER1 variation is more common than expected. If confirmed, these findings may inform future sequencing-based newborn screening programs for PPB, CN and SLCT, in which early detection improves prognosis.

Pleuropulmonary Blastoma: A Single-center Case Series of 6 Patients

Pleuropulmonary blastoma (PPB) is a rare malignancy of childhood which when left untreated often shows pathologic progression resulting in a more aggressive neoplasm with an increasingly poor prognosis. Because of this it is important to diagnose and initiate treatment early. However, early stage PPB can appear as a cystic lung lesion on imaging and can be easily misdiagnosed given the rarity of the malignancy. Moreover, current therapeutic guidelines for these lesions are not well established, making treatment decisions and management difficult for clinicians. DICER1 mutations are known to be present in a majority of PPBs with or without a germline mutation and may be part of a familial tumor predisposition syndrome. The clinical, pathologic, and genetic data of 6 patients are summarized here. Two patients with type I PPB and 4 patients with type II PPB underwent surgical and chemotherapeutic treatment and all are alive and without recurrence 1 to 13 years after treatment. With increasing awareness of PPB, it is important for clinicians to consider this malignant entity in the evaluation and treatment of patients presenting with a cystic lung abnormality, especially in cases with a history strongly suggestive of a DICER1 mutation.

DICER1-related Sertoli-Leydig cell tumor and gynandroblastoma: Clinical and genetic findings from the International Ovarian and Testicular Stromal Tumor Registry

BACKGROUND

Ovarian sex cord-stromal tumors (OSCST) include juvenile granulosa cell tumors (JGCT), Sertoli-Leydig cell tumor (SLCT) and gynandroblastoma (GAB) among others. These ovarian sex cord-stromal tumors as well as other tumors including pleuropulmonary blastoma (PPB) may be associated with DICER1 mutations. We sought to describe the clinical and genetic findings from the first 107 individuals enrolled in the International Ovarian and Testicular Stromal Tumor Registry.

METHODS

Medical and family history were obtained for individuals consecutively enrolled in the International Ovarian and Testicular Stromal Tumor Registry. Pathology was centrally reviewed. DICER1 sequencing was performed on blood and tumor tissue.

RESULTS

Of the 107 participants, 49 had SLCT, 25 had JGCT and 5 had GAB. Nearly all (36/37) SLCTs and 4/4 GAB tested had a DICER1 mutation in an RNase IIIb domain hotspot; approximately half of these individuals had a predisposing germline DICER1 mutation. Metachronous SLCTs were seen in 3 individuals with germline DICER1 mutations. Other DICER1-associated conditions were seen in 19% of patients with SLCT or GAB. Three children of women with SLCT were diagnosed with PPB based on genetic testing and clinical screening during the course of this study. All were diagnosed with PPB in its earliest and most curable form (Type I), were treated with surgery alone, and are alive without evidence of disease.

CONCLUSIONS

Recognition of the distinct genetic basis for a group of these tumors improves precise classification in difficult cases and promotes mutation-based screening and early detection.

Ovarian Sex Cord-Stromal Tumors

Ovarian sex cord-stromal tumors are clinically significant heterogeneous tumors that include several pathologic types. These tumors are often found in adolescents and young adults and can present with hormonal manifestations as well as signs and symptoms of a pelvic mass. Serum tumor markers may assist in preoperative diagnosis and surveillance. Several subtypes are associated with genetic predisposition, including those observed in patients with Peutz-Jegher syndrome. Recent studies have elucidated the relationship between Sertoli-Leydig cell tumors and DICER1 mutations. When classified as International Federation of Gynecology and Obstetrics stage Ia, most subtypes may be treated with surgery alone. Higher stage or recurrent tumors have variable prognoses that range from a usually rapid course in poorly differentiated Sertoli-Leydig cell tumor to an often prolonged course in adult granulosa cell tumors. New understanding of the molecular pathogenesis of these tumors may pave the way for novel therapeutics.

New roles for Dicer in the nucleolus and its relevance to cancer

The nucleolus is a distinct compartment of the nucleus responsible for ribosome biogenesis. Mis-regulation of nucleolar functions and of the cellular translation machinery has been associated with disease, in particular with many types of cancer. Indeed, many tumor suppressors (p53, Rb, PTEN, PICT1, BRCA1) and proto-oncogenes (MYC, NPM) play a direct role in the nucleolus, and interact with the RNA polymerase I transcription machinery and the nucleolar stress response. We have identified Dicer and the RNA interference pathway as having an essential role in the nucleolus of quiescent Schizosaccharomyces pombe cells, distinct from pericentromeric silencing, by controlling RNA polymerase I release. We propose that this novel function is evolutionarily conserved and may contribute to the tumorigenic pre-disposition of DICER1 mutations in mammals.

Pediatric Cystic Nephroma Is Morphologically, Immunohistochemically, and Genetically Distinct From Adult Cystic Nephroma

The term cystic nephroma has traditionally been used to refer to 2 neoplasms, a lesion in adults that is now thought to be part of the spectrum of mixed epithelial stromal tumor (MEST) and a pediatric lesion that has been associated with mutations in the DICER1 gene. A direct detailed morphologic, immunohistochemical, and genetic comparison of these 2 lesions has not been performed. In this study, we compare the morphologic features, immunoreactivity for estrogen receptor and inhibin, and DICER1 genetic status of 12 adult cystic nephroma/MEST (median age 50.5 y, all females) and 7 pediatric cystic nephroma (median age 1.3 y, male:female=6:1). Both lesions (11 of 12 adult cases, 6 of 7 pediatric cases) frequently demonstrated subepithelial accentuation of stromal cellularity, though the increased cellularity frequently included inflammatory cells in the pediatric cases. All adult and pediatric cases labeled for estrogen receptor; however, whereas most (83%) of adult cases labeled for inhibin at least focally, no pediatric case labeled for inhibin. Most adult cases (58%) demonstrated wavy, ropy collagen in association with cellular stroma, whereas this was not found in pediatric cases. 86% of pediatric cases demonstrated DICER1 mutations, whereas only 1 of 10 adult cases demonstrated a DICER1 mutation. In summary, although cellular stroma and estrogen receptor immunoreactivity are commonly present in both adult and pediatric cystic nephroma, ropy collagen and inhibin immunoreactivity are far more common in adult cystic nephroma/MEST, whereas DICER1 mutations are far more prevalent in pediatric cystic nephroma. These results support the current World Health Organization Classification's separation of adult and pediatric cystic nephromas as distinct entities.

Quantification of Thyroid Cancer and Multinodular Goiter Risk in the DICER1 Syndrome: A Family-Based Cohort Study

CONTEXT

The risk of thyroid cancer and multinodular goiter (MNG) in DICER1 syndrome, a rare tumor-predisposition disorder, is unknown.

OBJECTIVE

To quantify the risk of thyroid cancer and MNG in individuals with DICER1 syndrome.

DESIGN

Family-based cohort study.

SETTING

National Institutes of Health (NIH) Clinical Center (CC).

PARTICIPANTS

The National Cancer Institute DICER1 syndrome cohort included 145 individuals with a DICER1 germline mutation and 135 family controls from 48 families.

INTERVENTIONS

Each individual completed a detailed medical history questionnaire. A subset underwent a 3-day evaluation at the NIH CC.

MAIN OUTCOME MEASURES

The cumulative incidence of MNG (or thyroidectomy) was quantified using the complement of the Kaplan-Meier product limit estimator. We compared the observed number of thyroid cancers in the NCI DICER1 cohort with matched data from the Surveillance, Epidemiology, and End Results (SEER) Program. We performed germline and somatic (thyroid cancer, MNG) DICER1 sequencing.

RESULTS

By the age of 40 years, the cumulative incidence of MNG or thyroidectomy was 75% in women and 17% in men with DICER1 syndrome compared with 8% of control women (P < 0.001) and 0% of control men (P = 0.0096). During 3937 person-years of observation, individuals with DICER1 syndrome had a 16-fold increased risk of thyroid cancer (95% confidence interval, 4.3 to 41; P < 0.05) compared with the SEER rates. Of 19 MNG nodules and 3 thyroid cancers, 16 (84%) and 3 (100%), respectively, harbored germline and somatic pathogenic DICER1 mutations.

CONCLUSIONS

We propose a model of thyroid carcinogenesis in DICER1 syndrome. Early-onset, familial, or male MNG should prompt consideration of the presence of DICER1 syndrome.

Implementation of next generation sequencing into pediatric hematology-oncology practice: moving beyond actionable alterations

BACKGROUND

Molecular characterization has the potential to advance the management of pediatric cancer and high-risk hematologic disease. The clinical integration of genome sequencing into standard clinical practice has been limited and the potential utility of genome sequencing to identify clinically impactful information beyond targetable alterations has been underestimated.

METHODS

The Precision in Pediatric Sequencing (PIPseq) Program at Columbia University Medical Center instituted prospective clinical next generation sequencing (NGS) for pediatric cancer and hematologic disorders at risk for treatment failure. We performed cancer whole exome sequencing (WES) of patient-matched tumor-normal samples and RNA sequencing (RNA-seq) of tumor to identify sequence variants, fusion transcripts, relative gene expression, and copy number variation (CNV). A directed cancer gene panel assay was used when sample adequacy was a concern. Constitutional WES of patients and parents was performed when a constitutionally encoded disease was suspected. Results were initially reviewed by a molecular pathologist and subsequently by a multi-disciplinary molecular tumor board. Clinical reports were issued to the ordering physician and posted to the patient's electronic medical record.

RESULTS

NGS was performed on tumor and/or normal tissue from 101 high-risk pediatric patients. Potentially actionable alterations were identified in 38% of patients, of which only 16% subsequently received matched therapy. In an additional 38% of patients, the genomic data provided clinically relevant information of diagnostic, prognostic, or pharmacogenomic significance. RNA-seq was clinically impactful in 37/65 patients (57%) providing diagnostic and/or prognostic information for 17 patients (26%) and identified therapeutic targets in 15 patients (23%). Known or likely pathogenic germline alterations were discovered in 18/90 patients (20%) with 14% having germline alternations in cancer predisposition genes. American College of Medical Genetics (ACMG) secondary findings were identified in six patients.

CONCLUSIONS

Our results demonstrate the feasibility of incorporating clinical NGS into pediatric hematology-oncology practice. Beyond the identification of actionable alterations, the ability to avoid ineffective/inappropriate therapies, make a definitive diagnosis, and identify pharmacogenomic modifiers is clinically impactful. Taking a more inclusive view of potential clinical utility, 66% of cases tested through our program had clinically impactful findings and samples interrogated with both WES and RNA-seq resulted in data that impacted clinical decisions in 75% of cases.

Ovarian tumors related to intronic mutations in DICER1: a report from the international ovarian and testicular stromal tumor registry

Germline DICER1 mutations have been described in individuals with pleuropulmonary blastoma (PPB), ovarian Sertoli-Leydig cell tumor (SLCT), sarcomas, multinodular goiter, thyroid carcinoma, cystic nephroma and other neoplastic conditions. Early results from the International Ovarian and Testicular Stromal Tumor Registry show germline DICER1 mutations in 48 % of girls and women with SLCT. In this report, a young woman presented with ovarian undifferentiated sarcoma. Four years later, she presented with SLCT. She was successfully treated for both malignancies. Sequence results showed a germline intronic mutation in DICER1. This mutation results in an exact duplication of the six bases at the splice site at the intron 23 and exon 24 junction. Predicted improper splicing leads to inclusion of 10 bases of intronic sequence, frameshift and premature truncation of the protein disrupting the RNase IIIb domain. A second individual with SLCT was found to have an identical germline mutation. In each of the ovarian tumors, an additional somatic mutation in the RNase IIIb domain of DICER1 was found. In rare patients, germline intronic mutations in DICER1 that are predicted to cause incorrect splicing can also contribute to the pathogenesis of SLCT.

Pulmonary and pleural pathology: Contributions of Dr. Louis "Pepper" Dehner

Dr. Louis Dehner is an internationally renowned surgical pathologist who has published multiple textbooks and has authored or co-authored nearly 400 original articles in the medical literature. While many think of him as a pediatric pathologist, he has contributed to the literature across virtually the entire breadth of surgical pathology, and the lung and pleura is no exception. This review will highlight Dr. Dehner׳s contributions to the pulmonary and pleural pathology literature in the areas of infectious disease, medical lung disease and transplant pathology, and a number of neoplasms of the lung and pleura, with the remainder of this manuscript dedicated to the still evolving story of the pleuropulmonary blastoma as the signature contribution of his long and distinguished career.