Judicious DICER1 testing and surveillance imaging facilitates early diagnosis and cure of pleuropulmonary blastoma

Outcomes in ovarian Sertoli-Leydig cell tumor: A report from the International Pleuropulmonary Blastoma/DICER1 and Ovarian and Testicular Stromal Tumor Registries

OBJECTIVE

Sertoli-Leydig cell tumors (SLCTs) are rare sex cord-stromal tumors, representing <0.5% of all ovarian tumors. We sought to describe prognostic factors, treatment and outcomes for individuals with ovarian SLCT.

METHODS

Individuals with SLCT were enrolled in the International Pleuropulmonary Blastoma/DICER1 Registry and/or the International Ovarian and Testicular Stromal Tumor Registry. Medical records were systematically abstracted, and pathology was centrally reviewed when available.

RESULTS

In total, 191 participants with ovarian SLCT enrolled, with most (92%, 175/191) presenting with FIGO stage I disease. Germline DICER1 results were available for 156 patients; of these 58% had a pathogenic or likely pathogenic germline variant. Somatic (tumor) DICER1 testing showed RNase IIIb hotspot variants in 97% (88/91) of intermediately and poorly differentiated tumors. Adjuvant chemotherapy was administered in 40% (77/191) of cases, and among these, nearly all patients received platinum-based regimens (95%, 73/77), and 30% (23/77) received regimens that included an alkylating agent. Three-year recurrence-free survival for patients with stage IA tumors was 93.6% (95% CI: 88.2-99.3%) compared to 67.1% (95% CI: 55.2-81.6%) for all stage IC and 60.6% (95% CI: 40.3-91.0%) for stage II-IV (p < .001) tumors. Among patients with FIGO stage I tumors, those with mesenchymal heterologous elements treated with surgery alone were at higher risk for recurrence (HR: 74.18, 95% CI: 17.99-305.85).

CONCLUSION

Most individuals with SLCT fare well, though specific risk factors such as mesenchymal heterologous elements are associated with poor prognosis. We also highlight the role of DICER1 surveillance in early detection of SLCT, facilitating stage IA resection.

Prevalence of lung cysts in adolescents and adults with a germline DICER1 pathogenic/likely pathogenic variant: a report from the National Institutes of Health and International Pleuropulmonary Blastoma/DICER1 Registry

BACKGROUND

Pleuropulmonary blastoma (PPB), the hallmark tumour associated with DICER1-related tumour predisposition, is characterised by an age-related progression from a cystic lesion (type I) to a high-grade sarcoma with mixed cystic and solid features (type II) or purely solid lesion (type III). Not all cystic PPBs progress; type Ir (regressed), hypothesised to represent regressed or non-progressed type I PPB, is an air-filled, cystic lesion lacking a primitive sarcomatous component. This study aims to evaluate the prevalence of non-progressed lung cysts detected by CT scan in adolescents and adults with germline DICER1 pathogenic/likely pathogenic (P/LP) variants.

METHODS

Individuals were enrolled in the National Cancer Institute Natural History of DICER1 Syndrome study, the International PPB/DICER1 Registry and/or the International Ovarian and Testicular Stromal Tumor Registry. Individuals with a germline DICER1 P/LP variant with first chest CT at 12 years of age or older were selected for this analysis.

RESULTS

In the combined databases, 110 individuals with a germline DICER1 P/LP variant who underwent first chest CT at or after the age of 12 were identified. Cystic lung lesions were identified in 38% (42/110) with a total of 72 cystic lesions detected. No demographic differences were noted between those with lung cysts and those without lung cysts. Five cysts were resected with four centrally reviewed as type Ir PPB.

CONCLUSION

Lung cysts are common in adolescents and adults with germline DICER1 variation. Further study is needed to understand the mechanism of non-progression or regression of lung cysts in childhood to guide judicious intervention.

Type I and Ir pleuropulmonary blastoma (PPB): A report from the International PPB/DICER1 Registry

BACKGROUND

Pleuropulmonary blastoma (PPB) is the most common lung cancer of infancy and early childhood. Type I PPB is a purely cystic lesion that has a microscopic population of primitive small cells with or without rhabdomyoblastic features and may progress to type II or III PPB, whereas type Ir lacks primitive small cells.

METHODS

Children with suspected PPB were enrolled in the International PPB/DICER1 Registry. Pathology was centrally reviewed, and follow-up was ascertained annually.

RESULTS

Between 2006 and 2022, 205 children had centrally reviewed type I or Ir PPB; 39% of children with type I and 5% of children with type Ir PPB received chemotherapy. Outcomes were favorable, although 11 children (nine with type I and two with type Ir PPB) experienced progression to type II/III (n = 8) or regrowth of type I PPB at the surgical site (n = 3), none of whom received chemotherapy before progression. Age and cyst size in combination were more suitable than either factor alone in predicting whether a particular lesion was type I or Ir PPB.

CONCLUSIONS

For young children with type I PPB, outcomes are favorable, but complete resection is indicated because of the risk for progression. Chemotherapy may be useful in a subset of children at increased risk for recurrence/progression. Efforts to risk stratify children with type I PPB to optimize outcomes while reducing treatment-related side effects are underway.

DICER1 tumor predisposition syndrome: an evolving story initiated with the pleuropulmonary blastoma

DICER1 syndrome (OMIM 606241, 601200) is a rare autosomal dominant familial tumor predisposition disorder with a heterozygous DICER1 germline mutation. The most common tumor seen clinically is the pleuropulmonary blastoma (PPB), a lung neoplasm of early childhood which is classified on its morphologic features into four types (IR, I, II and III) with tumor progression over time within the first 4-5 years of life from the prognostically favorable cystic type I to the unfavorable solid type III. Following the initial report of PPB, its association with other cystic neoplasms was demonstrated in family studies. The detection of the germline mutation in DICER1 provided the opportunity to identify and continue to recognize a number seemingly unrelated extrapulmonary neoplasms: Sertoli-Leydig cell tumor, gynandroblastoma, embryonal rhabdomyosarcomas of the cervix and other sites, multinodular goiter, differentiated and poorly differentiated thyroid carcinoma, cervical-thyroid teratoma, cystic nephroma-anaplastic sarcoma of kidney, nasal chondromesenchymal hamartoma, intestinal juvenile-like hamartomatous polyp, ciliary body medulloepithelioma, pituitary blastoma, pineoblastoma, primary central nervous system sarcoma, embryonal tumor with multilayered rosettes-like cerebellar tumor, PPB-like peritoneal sarcoma, DICER1-associated presacral malignant teratoid neoplasm and other non-neoplastic associations. Each of these neoplasms is characterized by a second somatic mutation in DICER1. In this review, we have summarized the salient clinicopathologic aspects of these tumors whose histopathologic features have several overlapping morphologic attributes particularly the primitive mesenchyme often with rhabdomyoblastic and chondroid differentiation and an uncommitted spindle cell pattern. Several of these tumors have an initial cystic stage from which there is progression to a high grade, complex patterned neoplasm. These pathologic findings in the appropriate clinical setting should serve to alert the pathologist to the possibility of a DICER1-associated neoplasm and initiate appropriate testing on the neoplasm and to alert the clinician about the concern for a DICER1 mutation.

Pleuropulmonary blastoma in children and adolescents: The EXPeRT/PARTNER diagnostic and therapeutic recommendations

Pleuropulmonary blastoma (PPB) is a rare cancer occurring mainly during early childhood and often associated with germline DICER1 mutations. It is classified by the macroscopic appearance into three interrelated clinico-pathologic entities on a developmental continuum. Complete tumor resection is a main prognostic factor and can be performed at diagnosis or after neoadjuvant treatment that includes chemotherapy and in some cases radiotherapy. Optimal modalities of neo- or adjuvant treatments can be challenging taking into account potential long-term toxicities in this young population. This paper presents the recommendations for diagnosis and treatment of children and adolescents with PPB elaborated by the European Cooperative Study Group for Pediatric Rare Tumors (EXPeRT) within the European Union-funded project PARTNER (Paediatric Rare Tumours Network - European Registry).

Consensus recommendations from the EXPeRT/PARTNER groups for the diagnosis and therapy of sex cord stromal tumors in children and adolescents

As part of the European Union-funded project designated Paediatric Rare Tumours Network - European Registry (PARTNER), the European Cooperative Study Group for Pediatric Rare Tumors (EXPeRT) is continuously developing consensus recommendations in order to harmonize standard care for very rare solid tumors of children and adolescents. This paper presents the internationally recognized recommendations for the diagnosis and treatment of sex cord stromal tumors (SCST). The clinical approach to sex cord stromal tumors of the testis (TSCST) and ovary (OSCST) depends on histological differentiation and tumor stage. Virtually all TSCSTs present as localized nonmetastatic tumors, with excellent prognosis after complete resection. In contrast, the prognosis of OSCSTs may be adversely affected by tumor spillage during surgery or presence of metastases. In these cases, cisplatin-based chemotherapy is recommended. Of note, some SCSTs may develop in the context of tumor predisposition syndromes, for example, DICER-1, so that specific follow-up is indicated. SCSTs should be diagnosed and treated according to standardized recommendations that include reference pathology, genetic testing for tumor predisposition syndromes in selected cases, and stratified adjuvant chemotherapy in patients with unfavorable risk profile. To ensure high quality of diagnosis and therapy, patients should be enrolled into prospective registries.

Type II Pleuropulmonary Blastoma in a 4 Month Old Infant with Negative Dicer1 Mutation on Next Generation Sequencing

INTRODUCTION

Pleuropulmonary blastoma (PPB) is a rare, but aggressive tumor in the pediatric population. PPB is a dysontogenetic neoplasm of childhood that involves the lungs and/or pleura. Young relatives of children with PPB have an increased incidence of neoplasias and dysplasias. According to tumor tissue histopathology, PPB evolves from a cystic to solid state over time. PPBs can be sub-classified as type I (purely cystic), type II (having both cystic and solid elements), and type III (completely solid). Type II and type III tumors may be associated with metastasis, with the brain being the most common metastatic site. Due to the primitive nature of cells in the tumor mass, PPBs are very aggressive tumors that are resistant to therapy. The prognosis depends on the histopathology content and tumor type. Respiratory problems are the main complaint and diagnosis can be made only after additional examinations. Genetic relations through family members are associated with mutations in the DICER1 gene; between 60-80% of patients with PPBs are positive for DICER1 mutations. Mosaicism has also been reported.

AIM

The aim was to present a case of a 4 month-old infant with type II PPB, who had a negative result for DICER1 mutation in next generation sequencing. To detail the clinical presentation of this patient, we present radiographic and ultrasound findings and results of histopathological analysis, as well as genetic and scintigraphic findings and chemotherapy treatment.

CASE REPORT

Here we describe the genetic analysis of a patient with PPB who was negative for mutations in DICER1 and who had no relatives with disease. This patient underwent radical resection of the tumor and began therapy, but subsequently died after developing leukopenia and sepsis.

CONCLUSION

This case provides an example of a patient with PPB who was negative for DICER1 mutation upon genetic analysis and emphasizes the potential for disease that does not involve mutation of this gene.

A Genome-First Approach to Characterize DICER1 Pathogenic Variant Prevalence, Penetrance, and Phenotype

IMPORTANCE

Genetic disorders are historically defined through phenotype-first approaches. However, risk estimates derived from phenotype-linked ascertainment may overestimate severity and penetrance. Pathogenic variants in DICER1 are associated with increased risks of rare and common neoplasms and thyroid disease in adults and children. This study explored how effectively a genome-first approach could characterize the clinical traits associated with germline DICER1 putative loss-of-function (pLOF) variants in an unselected clinical cohort.

OBJECTIVE

To examine the prevalence, penetrance, and phenotypic characteristics of carriers of germline DICER1 pLOF variants via genome-first ascertainment.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study classifies DICER1 variants in germline exome sequence data from 92 296 participants of the Geisinger MyCode Community Health Initiative. Data for each MyCode participant were used from the start of the Geisinger electronic health record to February 1, 2018.

MAIN OUTCOMES AND MEASURES

Prevalence of germline DICER1 variation; penetrance of malignant tumors and thyroid disease in carriers of germline DICER1 variation; structured, manual review of electronic health records; and DICER1 sequencing of available tumors from an associated cancer registry.

RESULTS

A total of 92 296 adults (mean [SD] age, 59 [18] years; 98% white; 60% female) participated in the study. Germline DICER1 pLOF variants were observed in 1 in 3700 to 1 in 4600 participants, more than double the expected prevalence. Malignant tumors (primarily thyroid carcinoma) were observed in 4 of 25 participants (16%) with DICER1 pLOF variants, which is comparable (by 50 years of age) to the frequency of neoplasms in the largest registry- and clinic-based (phenotype-first) DICER1 studies published to date. DICER1 pLOF variants were significantly associated with risks of thyroidectomy (odds ratio [OR], 6.0; 95% CI, 2.2-16.3; P = .007) and thyroid cancer (OR, 9.2; 95% CI, 2.1-34.7; P = .02) compared with controls, but there was not a significant increase in the risk of goiter (OR, 1.8; 95% CI, 0.7-4.9). A female patient in her 80s who was a carrier of a germline DICER1 hotspot variant was apparently healthy on electronic health record review. The term DICER1 did not appear in any of the medical records of the 25 participants with a pLOF DICER1 variant, even in those affected with a known DICER1-associated tumor or thyroid phenotype.

CONCLUSIONS AND RELEVANCE

This cohort study was able to ascertain individuals with germline DICER1 variants based on a genome-first approach rather than through a previously established DICER1-related phenotype. Use of the genome-first approach may complement more traditional approaches to syndrome delineation and may be an efficient approach for risk estimation.

Germline predisposition to genitourinary rhabdomyosarcoma

Multiple genetic conditions predispose to the development of rhabdomyosarcoma. Much of the literature on rhabdomyosarcoma in genetic syndromes does not sub-divide the location or the pathology of the sarcomas. Therefore, there are limited data on genitourinary specific associations with certain genetic syndromes. We summarize, here, the primary differential considerations for rhabdomyosarcoma of the genitourinary system. Primary considerations include DICER1 pathogenic variation, Li-Fraumeni syndrome, constitutional mismatch repair deficiency, mosaic variegated aneuploidy, neurofibromatosis type 1, Noonan syndrome, other RASopathies, Costello syndrome, and Beckwith-Wiedemann syndrome. Some conditions may present with specific pathological, clinical and/or family history features, but for others, the genitourinary tumor may be the only presenting sign at the time of diagnosis. Genetic evaluation with counseling and/or testing may help identify an underlying tumor predisposition. This manuscript serves as an introduction to germline considerations for children with genitourinary rhabdomyosarcoma.

Pleuropulmonary blastoma-like peritoneal sarcoma: a newly described malignancy associated with biallelic DICER1 pathogenic variation

Since the original description of pathogenic germline DICER1 variation underlying pleuropulmonary blastoma (PPB), the spectrum of extrapulmonary neoplasms known to be associated with DICER1 has continued to expand and now includes tumors of the ovary, thyroid, kidney, eye, and brain among other sites. This report documents our experience with another manifestation: a primitive sarcoma that resembles PPB and DICER1-associated sarcoma of the kidney. These tumors are distinguished by their unusual location in the peritoneal cavity, associated with visceral and/or parietal mesothelium. A total of seven cases were identified through pathology review in children presenting at a median age of 13 years (range 3-14 years). Primary sites of origin included the fallopian tube (four cases), serosal surface of the colon (one case), and pelvic sidewall (two cases). One case had pathologic features of type I PPB, another type Ir (regressed) PPB, and the remaining five had features of type II or III PPB with a mixed primitive sarcomatous pattern with or without cystic elements. All had a pathogenic DICER1 variation identified in germline and/or tumor DNA. PPB-like peritoneal tumors represent a newly described manifestation of DICER1 pathogenic variation whose pathologic features are also recapitulated in DICER1-related renal sarcoma, cervical embryonal rhabdomyosarcoma, and some Sertoli-Leydig cell tumors with heterologous elements. Tumors arising from the fallopian tube or elsewhere in the abdomen/pelvis, especially those with heterogeneous rhabdomyosarcomatous and/or cartilaginous differentiation, should prompt consideration of germline and tumor DICER1 testing.

Practical roles for molecular diagnostic testing in ovarian adult granulosa cell tumour, Sertoli-Leydig cell tumour, microcystic stromal tumour and their mimics

Within the last decade, molecular advances have provided insights into the genetics of several ovarian sex cord-stromal tumours that have otherwise been enigmatic. Chief among these advances are the identification of FOXL2, DICER1 and CTNNB1 mutations in adult granulosa cell tumours, Sertoli-Leydig cell tumours (SLCTs), and microcystic stromal tumours (MCSTs), respectively. As access to molecular diagnostic laboratories continues to become more widely available, the potential roles for tumour mutation testing in the pathological diagnosis of these tumours merit discussion. Furthermore, links to inherited cancer susceptibility syndromes may exist for some women with SLCT (DICER1 syndrome) and MCST [familial adenomatous polyposis (FAP)]. This review will address practical issues in deciding when and how to apply mutation testing in the diagnosis of these three sex cord-stromal tumours. The pathologist's role in recommending referral for formal risk assessment for DICER1 syndrome and FAP will also be discussed.

DICER1 and FOXL2 Mutation Status Correlates With Clinicopathologic Features in Ovarian Sertoli-Leydig Cell Tumors

Sertoli-Leydig cell tumors (SLCTs) are rare ovarian sex cord-stromal neoplasms. The only known recurrent genetic abnormality is DICER1 mutation, with rare mutations reported in FOXL2. We set out to establish a molecular classifier using DICER1 and FOXL2 somatic mutation status and clinicopathologic features in 42 SLCTs. Five tumors (12%) were well differentiated, 31 (74%) moderately differentiated, and 6 (14%) poorly differentiated. Eight (19%) had heterologous elements, and 2 (5%) showed retiform differentiation; all 10 were moderately differentiated. DICER1 RNase IIIb domain mutations were identified in 18/41 (44%; 17 moderately, 1 poorly differentiated), including all cases with retiform or heterologous elements. FOXL2 c.402C>G (p.C134W) mutation was identified in 8/42 (19%) tumors (5 moderately, 3 poorly differentiated). DICER1 and FOXL2 mutations were mutually exclusive. Median age for the cohort was 47 years (range, 15 to 90 y). Patients with DICER1 mutations were younger (median, 24.5 y; range, 15 to 62 y) than patients with FOXL2 mutation (median, 79.5 y; range, 51 to 90 y) (P<0.0001). Nine of 10 tumors with retiform or heterologous elements occurred in premenopausal patients (median, 26.5 y; range, 15 to 57 y). Patients with tumors that were wild type for DICER1 and FOXL2 (15/42, 37%) had an intermediate age (median, 51 y; range, 17 to 74 y). All tumors were FOXL2 positive by immunohistochemistry. Patients with FOXL2 mutation trended toward presenting more often with abnormal bleeding (P=0.13); DICER1-mutant patients trended toward having more androgenic symptoms (P=0.22). Our data suggest at least 3 molecular subtypes of SLCT with distinct clinicopathologic features: DICER1 mutant (younger, more androgenic symptoms, moderately/poorly differentiated, retiform or heterologous elements), FOXL2 mutant (postmenopausal, abnormal bleeding, moderately/poorly differentiated, no retiform or heterologous elements), and DICER1/FOXL2 wild type (intermediate age, no retiform or heterologous elements, including all well-differentiated tumors).

Gynecologic and reproductive health in patients with pathogenic germline variants in DICER1

OBJECTIVE

Germline pathogenic variation in DICER1 underlies a tumor-predisposition disorder with increased risk for cervical embryonal rhabdomyosarcoma and ovarian sex-cord stromal tumors, particularly Sertoli-Leydig cell tumors. The gynecologic and reproductive health of these females has not yet been described.

METHODS

All female subjects recruited from November 2011 to July 2018 participating in an epidemiologic study of families with pathogenic DICER1 germline variation were included in this cross-sectional analysis. Participant evaluation included obstetric-gynecologic history, physical examination, hormone testing, pelvic ultrasound and record review.

RESULTS

Of 64 females aged 2-72 years, fifteen underwent treatment for pleuropulmonary blastoma as children and three were treated for cervical embryonal rhabdomyosarcoma. Of nine patients reporting a history of ovarian tumors, all presented with virilization or amenorrhea; eight occurred in adolescence. Post-pubertal females with no history of ovarian tumors experienced normal pubertal development, reported regular menstrual cycles, were fertile and underwent natural menopause at median age of 52 years. Thirty-two of 33 women who tried to conceive successfully delivered liveborn children. Of these 32, 10 experienced pregnancy-related thyroid enlargement resulting in thyroidectomy within one year of pregnancy; nine others had undergone pre-pregnancy thyroidectomy.

CONCLUSION

In these DICER1-carrier females, DICER1-related gynecological tumors occurred during childhood or adolescence in some after which women generally experienced healthy reproductive lives. Individual education and screening for these tumors is warranted. The high rate of DICER1-related multinodular goiter resulting in pre- and post-pregnancy thyroidectomy underscores the importance of thyroid monitoring during pregnancy to ensure maternal and fetal wellbeing.

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.

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.

Ovarian cancer in adolescents and young adults

The diagnosis of ovarian cancer in adolescents and young adults is always challenging. Many issues exist, and most important of these may be access to care with an appropriate provider. A range of histologies occur in the ovaries, and their frequency changes markedly as patients progress from adolescence to young adulthood. The very curable germ cell tumors of adolescence slowly give way to aggressive carcinomas, which require a different treatment approach. Special consideration is needed for treatment of toxicity. In an ideal world, centers consisting of pediatric, medical, and gynecological oncologists may be the most appropriate to care for these complex and diverse patients.

Case report: an identical twin with Sertoli-Leydig cell tumor

Our report details the workup and management of a 43-year-old woman with an identical twin who presented with 2 years of virilization and secondary amenorrhea. Serum total testosterone was elevated. An MRI did not identify adnexal or adrenal pathology. Subsequent ovarian vein sampling demonstrated unilateral testosterone elevation. The patient underwent laparoscopic unilateral oophorectomy resulting in the diagnosis of Sertoli-Leydig cell tumor (SLCT). Although SLCT is a rare sex-cord ovarian tumor, it is associated with endometrial hyperplasia and malignancy. Our goals are to review the workup of androgen-secreting tumors and discuss the clinical importance of the DICER1 mutation in the context of SLCT. In this case, an identical twin underwent DICER1 testing which was one of the essential steps in her clinical management.

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.

DICER1 gene mutations in endocrine tumors

In this review, the importance of the DICER1 gene in the function of endocrine cells is discussed. There is conclusive evidence that DICER1 mutations play a crucial role in the development, progression, cell proliferation, therapeutic responsiveness and behavior of several endocrine tumors. We review the literature of DICER1 gene mutations in thyroid, parathyroid, pituitary, pineal gland, endocrine pancreas, paragangliomas, medullary, adrenocortical, ovarian and testicular tumors. Although significant progress has been made during the last few years, much more work is needed to fully understand the significance of DICER1 mutations.

Uncommon hereditary gynaecological tumour syndromes: pathological features in tumours that may predict risk for a germline mutation

The most common hereditary gynaecological tumour syndromes are hereditary breast and ovarian cancer syndrome and Lynch syndrome. However, pathologists also may encounter gynaecological tumours in women with rare hereditary syndromes. Many of these tumours exhibit distinctive gross and microscopic features that are associated with a risk for an inherited gene mutation. The sensitivity and specificity of these tumour pathology features for predicting an inherited mutation vary depending on the syndrome. By recognising these tumour features, pathologists may potentially contribute to the diagnosis of an unsuspected syndrome by recommending referral of the patient for formal risk assessment by genetic counselling. Patients additionally benefit from diagnosis of an inherited syndrome because many also carry a lifetime risk for developing primary malignancies outside of the gynaecological tract. Early diagnosis of an inherited syndrome permits early screening, detection, and management of additional malignancies associated with the syndrome. This review highlights these rare syndromes and their tumour pathology, including Peutz-Jeghers syndrome (gastric type mucinous carcinoma of the cervix; ovarian sex cord tumour with annular tubules); hereditary leiomyoma renal cell carcinoma syndrome (uterine leiomyoma); tuberous sclerosis complex (uterine PEComa; uterine lymphangioleiomyomatosis); DICER1 syndrome (ovarian Sertoli-Leydig cell tumour; cervical embryonal rhabdomyosarcoma); rhabdoid tumour predisposition syndrome 2 (small cell carcinoma of the ovary, hypercalcaemic type); Cowden syndrome (endometrial endometrioid adenocarcinoma); naevoid basal cell carcinoma syndrome (ovarian fibroma); and Von Hippel-Lindau syndrome (clear cell papillary cystadenoma of the broad ligament).

DICER1 syndrome: Approach to testing and management at a large pediatric tertiary care center

BACKGROUND

To expand the current knowledge of DICER1 syndrome and to propose criteria for genetic testing based on experience at a pediatric tertiary care center.

PROCEDURE

This study involved a retrospective chart review of the 78 patients (47 probands and 31 family members) seen in the Cancer Genetics Program at The Hospital for Sick Children (SickKids) who were offered genetic testing for DICER1.

RESULTS

Of 47 probands offered genetic testing for DICER1, 46 pursued testing: 11 (23.9%) carried a pathogenic variant and one proband (2.1%) carried a missense variant of uncertain significance with evidence for pathogenicity. Thirty-one family members of variant-positive probands were offered testing: eight of the 25 who agreed to testing carried their familial variant (32.0%). Overall, 20 patients were identified to have a variant in DICER1 (eight males, 12 females). Of these, 13 (65.0%) presented with clinical manifestations associated with the syndrome. The most common lesions were pleuropulmonary blastoma (PPB) (five of 20 patients, 25.0%) and pineoblastoma (three of 20 patients, 15.0%). The average age at which individuals were diagnosed with a primary neoplasm was 5.2 years (range 0.8-20 years, median 3.0). Surveillance at our institution, with a median follow-up time of 23 months, has identified PPB in two asymptomatic individuals. These lesions were identified at early stages, thus potentially reducing treatment-related morbidity and mortality.

CONCLUSION

This study further delineates the DICER1 syndrome phenotype and demonstrates the feasibility of a DICER1 syndrome surveillance protocol for the early detection of tumors.

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.

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.

DICER1 mutation and tumors associated with a familial tumor predisposition syndrome: practical considerations

The familial tumor predisposition syndrome known as DICER1-pleuropulmonary blastoma (PPB) or DICER1 tumor predisposition syndrome was first described in 2009, and it involves an increased risk in the occurrence of various tumors, like cystic nephroma and PPB. Here is presented a girl with a cystic nephroma and two cystic lung lesions who was diagnosed years later with the DICER1 gene mutation. This mutation was also found in one of her parents. Thus, the screening for the DICER1 gene mutation may be important in children with certain/multiple tumors and their families.

The natural history of prenatally diagnosed congenital cystic lung lesions: long-term follow-up of 119 cases

BACKGROUND

A paucity of evidence regarding the natural history of congenital pulmonary airway malformations (CPAMs) and pulmonary sequestration (PS) has resulted in a divergence in management strategy of asymptomatic cases.

METHODS

We describe the long-term clinical course of 119 children diagnosed with these lesions treated at Great Ormond Street Hospital (GOSH). Cases were identified via the GOSH patient database. Study entry required the identification of a cystic lung lesion on prenatal ultrasound and confirmation of CPAM/PS on postnatal CT imaging. Patients followed up for at least 5 years were included.

RESULTS

51 (43%) patients were managed surgically; 8 (6.7%) as an emergency during the neonatal period, 6 (5.1%) electively due to concerning features on CT scan, 20 (17%) following medical advice, 1 (0.8%) following a severe respiratory infection and in 5 (4.2%) the indication was unclear. The indication in 11 (9.2%) was recurrent respiratory infection and median age at surgery was 1.6 years (range 0.4 to 4.6 years). No cases of malignancy were identified on histological examination of resected lesions. 68 (57%) patients were managed conservatively for a median period of 9.9 years (range 5.2 years to 18 years). Seven (10%) were discharged, one was followed-up elsewhere (1.5%) and eight (11%) were lost to follow-up. In four patients (5.9%), the lesion resolved spontaneously. 52 (76%) continue to be followed-up and remain asymptomatic.

CONCLUSIONS

This is one of the largest case series documenting the natural history of CPAMs and PS following a prenatal diagnosis and demonstrates that conservative management is a reasonable option in selected cases.

Pediatric imaging in DICER1 syndrome

BACKGROUND

DICER1 syndrome, arising from a mutation in the DICER1 gene mapped to chromosome 14q32, is associated with an increased risk of a range of benign and malignant neoplasms.

OBJECTIVE

To determine the spectrum of abnormalities and imaging characteristics in patients with DICER1 syndrome at a tertiary pediatric hospital.

MATERIALS AND METHODS

This retrospective analysis evaluated imaging in patients ≤18 years with DICER1 germline variants between January 2004 and July 2016. An imaging database search including keywords pleuropulmonary blastoma, cystic nephroma, pineoblastoma, embryonal rhabdomyosarcoma, ovarian sex cord-stromal tumor, ovarian Sertoli-Leydig cell tumor and DICER1 syndrome, was cross-referenced against the institutional Cancer Genetics Program database, excluding patients with negative/unknown DICER1 gene testing.

RESULTS

Sixteen patients were included (12 females; mean age at presentation: 4.2 years, range: 14 days to 17 years), with surveillance imaging encompassing the following modalities: chest X-ray and CT; abdominal, pelvic and neck US; and brain and whole-body MRI. Malignant lesions (68.8% of patients) included pleuropulmonary blastoma (5), pineoblastoma (3), ovarian Sertoli-Leydig cell tumor (1), embryonal rhabdomyosarcoma (1) and renal sarcoma (1); benign lesions (37.5% of patients) included thyroid cysts (2), thyroid nodules (2), cystic nephroma (2), renal cysts (1) and pineal cyst (1). A common lesional appearance observed across modalities and organs was defined as the "cracked windshield" sign.

CONCLUSION

The spectrum of DICER1-related tumors and the young age at presentation suggest early surveillance of at-risk patients is critical, while minimizing exposure to ionizing radiation.

Multimorbidity and Genetic Characteristics of DICER1 Syndrome Based on Systematic Review

It has been reported that germline DICER1 mutations correlate with a distinctive human disease syndrome. Many published studies within this field have been conducted based on rare cases. We systematically searched bibliographic databases, including PubMed, Embase, and COSMIC for articles which are related to diseases covered by DICER1 syndrome. The weighted summary of mutation frequencies among patients with pleuropulmonary blastoma (PPB), cystic nephroma (CN), and Sertoli-Leydig cell tumor (SLCT) were calculated. Forty-nine eligible articles were included. In total, 72 cases with multimorbidity of DICER1 syndrome were identified. More females (n=46, 64%) presented with multimorbidity than males (n=18, 25%) and the remaining 8 patients' sex were unknown. Nineteen of 72 patients with multimorbidity suffered from another disease that was not yet included in DICER1 syndrome, which would provide potential phenotypes of DICER1 syndrome. The germline DICER1 mutation frequencies in PPB, CN, and SLCT were 66.9%, 73.2%, and 57.1%, respectively. The somatic DICER1 mutation frequencies of PPB, CN, and SLCT were 92.4%, 87.9%, and 43.3%, respectively. Majority of patients with multimorbidity of DICER1 syndrome were mutation positive individuals so that multimorbidity may suggest the possible germline mutation of these patients and their relatives.

Metachronous Type I pleuropulmonary blastoma and atypical choroid plexus papilloma in a young child

Pleuropulmonary blastoma (PPB) is a rare childhood tumor, often associated with germline DICER1 mutations and a risk for development of other benign and malignant tumors, a constellation termed DICER1 syndrome. A 1-year-old male was diagnosed with Type I PPB and screened regularly thereafter for detection of intrathoracic and intraabdominal disease. Ten months after diagnosis of PPB, he presented with headaches and vomiting. He was diagnosed with atypical choroid plexus papilloma, a lesion not previously reported with PPB. The presence of central nervous system symptoms in patients with PPB or a phenotype suggestive of DICER1 syndrome should prompt early intracranial imaging.

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.

Macrocephaly associated with the DICER1 syndrome

Background

Germline mutations in DICER1 increase the risk of various tumors, including pleuropulmonary blastoma. Macrocephaly and symmetric overgrowth has been reported in some, but not all, patients with mosaic DICER1 RNase IIIb mutations; the prevalence of these features in individuals with constitutional germline DICER1 mutations is unknown.

Methods

We analyzed prospectively collected auxology data from 67 DICER1 mutation carriers and 43 family controls. We assessed differences between groups using an exact test for proportions and generalized estimating equations for continuous dependent variables.

Results

Twenty-eight DICER1 mutation carriers (42%) were macrocephalic, and none had an occipital-frontal circumference (OFC) below the 3^rd centile, which significantly differed from family controls, of whom five were macrocephalic (12%) and two had OFC below the 3^rd centile (5%) (P<0.001). DICER1 mutation carriers were taller than familial controls after controlling for gender (P=0.048), but similar proportions of both groups were above the 97^th centile of population norms. Head circumference remained increased after adjusting for differences in height.

Conclusions

For the first time, we establish macrocephaly as a common finding in the DICER1 syndrome. Like some of the other tumor-predisposition disorders, macrocephaly may be a useful, albeit a subtle, clinical clue to the DICER1 syndrome diagnosis.

Evolution of Renal Cysts to Anaplastic Sarcoma of Kidney in a Child With DICER1 Syndrome

Anaplastic sarcoma of kidney (ASK) is a rare neoplasm recently associated with DICER1 mutations. We report a child with germline DICER1 mutation who developed ASK in preexisting septated renal cysts, which were likely cystic nephroma. From age 2.5 to 6 years, sonographic imaging illustrated changes in the size and number of renal cysts, followed at age 8.8 years by a mass, pathologically an ASK. Lung cysts resected in infancy were diagnosed retrospectively as pleuropulmonary blastoma. Both tumors had acquired somatic DICER1 mutations. Ultrasonographic evolution of renal cysts to ASK has not previously been documented. Children with both pulmonary and renal cysts are candidates for DICER1 mutation testing.

Rare Tumors in Children: Progress Through Collaboration

Rare pediatric tumors account for approximately 10% of all childhood cancers, which in themselves are a rare entity. The diverse histologies and clinical behaviors of rare pediatric tumors pose challenges to the investigation of their biologic and clinical features. National and international cooperative groups such as the Rare Tumor Committee of the Children's Oncology Group, Rare Tumors in Pediatric Age Project, and European Cooperative Study Group for Pediatric Rare Tumors have developed several initiatives to advance knowledge about rare pediatric cancers. However, these programs have been only partially effective, necessitating the development of alternative mechanisms to study these challenging diseases. In this article, we review the current national and international collaborative strategies to study rare pediatric cancers and alternative methods under exploration to enhance those efforts, such as independent registries and disease-specific, National Cancer Institute-sponsored clinics.

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

Pleuropulmonary blastoma (PPB) is the most frequent pediatric lung tumor and often the first indication of a pleiotropic cancer predisposition,  DICER1 syndrome, comprising a range of other individually rare, benign and malignant tumors of childhood and early adulthood. The genetics of  DICER1-associated tumorigenesis are unusual in that tumors typically bear neomorphic missense mutations at one of five specific “hotspot” codons within the RNase IIIb domain of  DICER 1, combined with complete loss of function (LOF) in the other allele. We analyzed a cohort of 124 PPB children for predisposing  DICER1 mutations and sought correlations with clinical phenotypes. Over 70% have inherited or  de novo germline LOF mutations, most of which truncate the  DICER1 open reading frame. We identified a minority of patients who have no germline mutation, but are instead mosaic for predisposing  DICER1 mutations. Mosaicism for RNase IIIb domain hotspot mutations defines a special category of  DICER1 syndrome patients, clinically distinguished from those with germline or mosaic LOF mutations by earlier onsets and numerous discrete foci of neoplastic disease involving multiple syndromic organ sites. A final category of PBB patients lack predisposing germline or mosaic mutations and have sporadic (rather than syndromic) disease limited to a single PPB tumor bearing tumor-specific RNase IIIb and LOF mutations. We propose that acquisition of a neomorphic RNase IIIb domain mutation is the rate limiting event in  DICER1-associated  tumorigenesis, and that distinct clinical phenotypes associated with mutational categories reflect the temporal order in which LOF and RNase IIIb domain mutations are acquired during development.

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

Pleuropulmonary blastoma (PPB) is the most frequent pediatric lung tumor and often the first indication of a pleiotropic cancer predisposition,  DICER1 syndrome, comprising a range of other individually rare, benign and malignant tumors of childhood and early adulthood. The genetics of  DICER1-associated tumorigenesis are unusual in that tumors typically bear neomorphic missense mutations at one of five specific "hotspot" codons within the RNase IIIb domain of  DICER 1, combined with complete loss of function (LOF) in the other allele. We analyzed a cohort of 124 PPB children for predisposing  DICER1 mutations and sought correlations with clinical phenotypes. Over 70% have inherited or  de novo germline LOF mutations, most of which truncate the  DICER1 open reading frame. We identified a minority of patients who have no germline mutation, but are instead mosaic for predisposing  DICER1 mutations. Mosaicism for RNase IIIb domain hotspot mutations defines a special category of  DICER1 syndrome patients, clinically distinguished from those with germline or mosaic LOF mutations by earlier onsets and numerous discrete foci of neoplastic disease involving multiple syndromic organ sites. A final category of PBB patients lack predisposing germline or mosaic mutations and have sporadic (rather than syndromic) disease limited to a single PPB tumor bearing tumor-specific RNase IIIb and LOF mutations. We propose that acquisition of a neomorphic RNase IIIb domain mutation is the rate limiting event in  DICER1-associated  tumorigenesis, and that distinct clinical phenotypes associated with mutational categories reflect the temporal order in which LOF and RNase IIIb domain mutations are acquired during development.

[Specificities of sex-cord stromal tumors in children and adolescents]

Sex-cord stromal tumors (SCT) are rare pediatric tumors accounting for less than 5% of gonadal tumors in children and adolescents. They differ from those diagnosed in adults by their presentation, histology, evolution and treatment modalities. Testicular SCT occur mostly in infants less than 6 months. Testicular swelling is often the only symptom, but signs of hormonal secretion with gynecomastia may be present. Juvenile granulosa SCT is the main histologic subtype. Sertoli SCTs are much less frequent while Leydig tumors occurred in older children and adolescents. Prognosis is excellent after inguinal orchiectomy. Testis sparing surgery could be performed but indications and modalities have to be strongly defined. Ovarian SCT are diagnosed in older children and adolescents and present with abdominal symptoms and/or signs of hormonal secretion: estrogenic manifestations (isosexual pseudoprecocity, menometrorrhagia) or virilization (hirsutism, amenorrhea). Main histologic subtype is juvenile granulosa (rarely Sertoli-Leydig). If oophorectomy (or salpingo-oophorectomy) may be curative for localized disease, adjuvant cisplatin-containing chemotherapy is mandatory in case of tumor rupture or peritoneal dissemination to prevent recurrences. Because of the rarity of these pediatric tumors, concerted multidisciplinary cares are required to best adapt therapeutic strategy before any surgical intervention.

Pleuropulmonary blastoma: a report on 350 central pathology-confirmed pleuropulmonary blastoma cases by the International Pleuropulmonary Blastoma Registry

BACKGROUND

Pleuropulmonary blastoma (PPB) has 3 subtypes on a tumor progression pathway ranging from type I (cystic) to type II (cystic/solid) and type III (completely solid). A germline mutation in DICER1 is the genetic cause in the majority of PPB cases.

METHODS

Patients confirmed to have PPB by central pathology review were included, and their clinical characteristics and outcomes were reported. Germline DICER1 mutations were sought with Sanger sequencing.

RESULTS

There were 435 cases, and a central review confirmed 350 cases to be PPB; 85 cases (20%) were another entity. Thirty-three percent of the 350 PPB cases were type I or type I regressed (type Ir), 35% were type II, and 32% were type III or type II/III. The median ages at diagnosis for type I, type II, and type III patients were 8, 35, and 41 months, respectively. The 5-year overall survival (OS) rate for type I/Ir patients was 91%; all deaths in this group were due to progression to type II or III. OS was significantly better for type II versus type III (P = .0061); the 5-year OS rates were 71% and 53%, respectively. Disease-free survival (DFS) was also significantly better for type II versus type III (P = .0002); the 5-year DFS rates were 59% and 37%, respectively. The PPB type was the strongest predictor of outcome. Metastatic disease at the diagnosis of types II and III was also an independent unfavorable prognostic factor. Sixty-six percent of the 97 patients tested had a heterozygous germline DICER1 mutation. In this subset, the DICER1 germline mutation status was not related to the outcome.

CONCLUSIONS

Cystic type I/Ir PPB has a better prognosis than type II, and type II has a better outcome than type III. Surveillance of DICER1 carriers may allow the earlier detection of cystic PPB before its progression to type II or III PPB and thereby improve outcomes.

Management of familial cancer: sequencing, surveillance and society

The clinical management of familial cancer begins with recognition of patterns of cancer occurrence suggestive of genetic susceptibility in a proband or pedigree, to enable subsequent investigation of the underlying DNA mutations. In this regard, next-generation sequencing of DNA continues to transform cancer diagnostics, by enabling screening for cancer-susceptibility genes in the context of known and emerging familial cancer syndromes. Increasingly, not only are candidate cancer genes sequenced, but also entire 'healthy' genomes are mapped in children with cancer and their family members. Although large-scale genomic analysis is considered intrinsic to the success of cancer research and discovery, a number of accompanying ethical and technical issues must be addressed before this approach can be adopted widely in personalized therapy. In this Perspectives article, we describe our views on how the emergence of new sequencing technologies and cancer surveillance strategies is altering the framework for the clinical management of hereditary cancer. Genetic counselling and disclosure issues are discussed, and strategies for approaching ethical dilemmas are proposed.

Germ-line and somatic DICER1 mutations in pineoblastoma

Germ-line RB-1 mutations predispose to pineoblastoma (PinB), but other predisposing genetic factors are not well established. We recently identified a germ-line DICER1 mutation in a child with a PinB. This was accompanied by loss of heterozygosity (LOH) of the wild-type allele within the tumour. We set out to establish the prevalence of DICER1 mutations in an opportunistically ascertained series of PinBs. Twenty-one PinB cases were studied: Eighteen cases had not undergone previous testing for DICER1 mutations; three patients were known carriers of germ-line DICER1 mutations. The eighteen PinBs were sequenced by Sanger and/or Fluidigm-based next-generation sequencing to identify DICER1 mutations in blood gDNA and/or tumour gDNA. Testing for somatic DICER1 mutations was also conducted on one case with a known germ-line DICER1 mutation. From the eighteen PinBs, we identified four deleterious DICER1 mutations, three of which were germ line in origin, and one for which a germ line versus somatic origin could not be determined; in all four, the second allele was also inactivated leading to complete loss of DICER1 protein. No somatic DICER1 RNase IIIb mutations were identified. One PinB arising in a germ-line DICER1 mutation carrier was found to have LOH. This study suggests that germ-line DICER1 mutations make a clinically significant contribution to PinB, establishing DICER1 as an important susceptibility gene for PinB and demonstrates PinB to be a manifestation of a germ-line DICER1 mutation. The means by which the second allele is inactivated may differ from other DICER1-related tumours.

DICER1: mutations, microRNAs and mechanisms

Dicer is central to microRNA-mediated silencing and several other RNA interference phenomena that are profoundly embedded in cancer gene networks. Most recently, both germline and somatic mutations in DICER1 have been identified in diverse types of cancer. Although some of the mutations clearly reduce the dosage of this key enzyme, others dictate surprisingly specific changes in select classes of small RNAs. This Review reflects on the molecular properties of the Dicer enzymes in small RNA silencing pathways, and rationalizes the newly discovered mutations on the basis of the activities and functions of its determinants.