Recurrent genetic alterations in epigenetically defined pineoblastoma subtypes.

Introduction: Genome-wide methylation analyses recently revealed novel epigenetic pineoblastoma (PBL) subtypes, but so far few data are available on recurrent cytogenetic alterations due to the rarity of these neoplasms. Therefore, our aim was to shed further light onto the molecular and genetic characteristics underlying the pathogenesis of pineoblastoma subtypes. Experimental procedures: Cytogenetic alterations of tumor samples of 60 patients with a diagnosis of PBL confirmed by reference neuropathology and methylation array profiling (450K or EPIC BeadChips (Illumina)) were analyzed by high-resolution genome-wide molecular inversion probe analysis. 52 cases could be screened for mutations by next-generation DNA panel sequencing. Survival data of 41 patients were available. All patients had surgery and older patients (≥4y) received RT followed by maintenance chemotherapy (n=37); infants (<4y) were primarily given a RT-sparing regimen that involved intensified chemotherapy dosage. Results: Of the recently published epigenetic consensus PBL subtypes (Liu et al., 2021), our cohort consisted of 37 PBL-miRNA1 (1A, 30; 1B, 7), 17 PBL-miRNA2, 2 PBL-MYC/FOXR2, and 4 PBL-RB1 samples. PBL-miRNA subtype tumors had characteristic alterations in microRNA-processing genes; DICER1 mutations (n=14; 4 in Grp1A/1 in Grp1B/9 in Grp2) were most abundant, followed by homozygous deletions of the DROSHA locus (n=11; 8/1/2) and DROSHA mutations (n=9; 3/3/3). Most frequent cytogenetic aberrations in these subtypes were chromosome (chr.) 7 gains (n=25) and chr. 14 losses (n=20, with all but one of miRNA2 cases). DICER1 mutations were significantly associated with chr. 14 losses (p<0.001). 17 cases showed gains of the chromosomal arm 14q, in 6 additional cases, focal gains were found of the OTX2 oncogene located on chr. 14q. In the miRNA subtypes we identified cases with a tetraploid phenotype (n=11; 7/4/0). Interestingly, none of the 6 patients with tetraploid tumors and survival data had relapses, while the remaining patients of the miRNA subtypes had a 5-year PFS of 72% and 5-year OS of 68% (10 of 31 with relapse/death) after a median follow-up time of 3.9 years. However, this did not reach statistical significance. A significant impact on survival could not be demonstrated for chr. 14q gains or focal OTX2 gains. The PBL-RB1 subtype cases had homozygous RB1 deletions (n=3) or biallelic RB1 mutations (n=1). Focal chromosomal aberrations were frequently found in this subtype, but rarely numerical alterations. Conclusion: The epigenetically defined PBL subtypes were characterized by distinct cytogenetic and mutational events. Although we could not demonstrate a prognostic impact of these events, this might be due to the small sample size. A possible prognostic role for a superior (e.g. tetraploidy) or inferior outcome (e.g. OTX2 gains) need studies in larger cohorts and ideally in prospective clinical trials. Citation Format: Tobias Goschzik, Mathias Yuan, Martin Mynarek, Elke Pfaff, Evelyn Dörner, David T. Jones, Stefan M. Pfister, Stefan Rutkowski, Torsten Pietsch. Recurrent genetic alterations in epigenetic pineoblastoma subtypes. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3561.

INTRODUCTIONGenome-wide methylation analyses recently revealed distinct epigenetic pineoblastoma (PBL) subtypes. The aim of the study was to shed further light onto the genetic characteristics underlying the pathogenesis of pineoblastoma subtypes. METHODSCytogenetic alterations of tumor samples of 76 patients with a diagnosis of PBL confirmed by reference neuropathology and methylation-based subtyping were analyzed by high-resolution genome-wide molecular inversion probe analysis. Seventy-two cases were screened for mutations by next-generation DNA panel sequencing. Survival data of 49 patients were available. Patients ≥4y received postoperative RT followed by maintenance chemotherapy (n=42); infants (<4y) were primarily treated on RT-sparing regimens with intensified chemotherapy. RESULTSAccording to epigenetic consensus PBL subtypes (Liu et al., 2021), our cohort consisted of 48 PBL-miRNA1 (1A=40; 1B=8), 17 PBL-miRNA2, 4 PBL-MYC/FOXR2, and 7 PBL-RB1 samples. PBL-miRNA subtype tumors had characteristic alterations in microRNA-processing genes; DICER1 mutations (n=18) and homozygous deletions of the DROSHA locus (n=17) were most abundant, followed by DROSHA mutations (n=12). Most frequent cytogenetic aberrations in PBL-miRNA were whole chromosome (chr.) 7 gain (n=30) and chr. 14 loss (n=21). DICER1 mutations were significantly associated with chr. 14 loss (p<0.001). Twenty-one cases showed gains of chr. 14, 8 additional cases gains of the OTX2 oncogene (chr. 14q). In the miRNA subtypes we identified cases with polyploid cytogenetics (n=15). Of note, only one of the 8 patients with polyploid tumors and survival data died, while the remaining patients of the miRNA subtypes had a 5-year PFS/OS of 61.46±9.27/63.24±9.23% (14 of 35 died) after a median follow-up time of 5.52 years. However, this comparison did not reach statistical significance (p=0.25). CONCLUSIONThe epigenetically defined PBL-miRNA subtypes are characterized by distinct cytogenetic and mutational events. A possible prognostic role for a superior (e.g. polyploidy) or inferior outcome requires investigation in prospective clinical trials.

Tumors of the pineal region comprise several different entities with distinct clinical and histopathological features. Whereas some entities predominantly affect adults, pineoblastoma (PB) constitutes a highly aggressive malignancy of childhood with a poor outcome. PBs mainly arise sporadically, but may also occur in the context of cancer predisposition syndromes including DICER1 and RB1 germline mutation. With this study, we investigate clinico-pathological subgroups of pineal tumors and further characterize their biological features. We performed genome-wide DNA methylation analysis in 195 tumors of the pineal region and 20 normal pineal gland controls. Copy-number profiles were obtained from DNA methylation data; gene panel sequencing was added for 93 tumors and analysis was further complemented by miRNA sequencing for 22 tumor samples. Unsupervised clustering based on DNA methylation profiling separated known subgroups, like pineocytoma, pineal parenchymal tumor of intermediate differentiation, papillary tumor of the pineal region and PB, and further distinct subtypes within these groups, including three subtypes within the core PB subgroup. The novel molecular subgroup Pin-RB includes cases of trilateral retinoblastoma as well as sporadic pineal tumors with RB1 alterations, and displays similarities with retinoblastoma. Distinct clinical associations discriminate the second novel molecular subgroup PB-MYC from other PB cases. Alterations within the miRNA processing pathway (affecting DROSHA, DGCR8 or DICER1) are found in about two thirds of cases in the three core PB subtypes. Methylation profiling revealed biologically distinct groups of pineal tumors with specific clinical and molecular features. Our findings provide a foundation for further clinical as well as molecular and functional characterization of PB and other pineal tumors, including the role of miRNA processing defects in oncogenesis.

Pineal parenchymal tumours (PPTs) are rare neoplasms that are divided into pineocytoma (PC), pineoblastoma (PB) and PPT of intermediate differentiation (PPTID). Factors affecting the survival of patients with PPTs are morphological subtype and histological grading according to mitotic index and neurofilament immunostaining. Grading criteria to distinguish PPTIDs are difficult to define, particularly when using small specimens. The Ki67 labelling index (LI) might be helpful in distinguishing between grade II and III PPTIDs. Our study was performed to assess the predictive value of the Ki67 LI in a large cooperative series of PPTs and to evaluate whether inclusion of this data would improve and refine the World Health Organization classification. A retrospective analysis of 33 PPTs was performed. The histological features of the tumours were reviewed and Ki67 LI scoring was evaluated by immunohistochemistry. Data were correlated with the patients' survival. The mean Ki67 LI was significantly different for tumour grades (0 in PC, 5.2 ± 0.4 in PPTID grade II, 11.2 ± 2.0 in PPTID grade III, 36.4 ± 6.2 in PB; P < 0.0001). However, there was no statistically significant difference in either overall or disease-free survival evaluated by the Kaplan-Meier method for patients with different grade tumours or Ki67 LI, possibly due to the different clinical management of patients in different centres. The Ki67 LI may be a useful additional tool for grading PPTs, more particularly in small tumour samples.

403P - Pineal parenchymal tumors: Patterns of care from a tertiary cancer centre in India

The pineal parenchymal tumors are rare, comprising 15-30% of all tumors of pineal region. Their histological classification alone has been found to be inadequate for prognostication. Hence, we correlated their immunohistochemical profile with the prognosis. A retrospective analysis of 33 pineal parenchymal tumors treated from 1990-2004 was performed. The histological features of the tumors were reviewed and immunohistochemical staining for neurofilament protein (NF), MIB-1, synaptophysin and GFAP were performed. Results were correlated with the patients' survival. The study comprised 6 pineocytomas (PC), 17 pineoblastomas (PB) and 10 pineal parenchymal tumors with intermediate differentiation (PPT-ID) which included 3 mixed PC/PB. The histological diagnosis was obtained from microsurgical biopsy/decompression, stereotactic or endoscopic biopsy. Adjuvant therapy was advised based on histology. All pineocytomas stained positive for NF. Most pineoblastomas (13/16) failed to show any immunoreactivity with NF. The mean MIB-1 labeling index in pineocytomas, PPT of ID and pineoblastomas were 1.58, 16.1 and 23.52 respectively (p < 0.001). All the tumors stained positive for synaptophysin, although the intensity of the staining varied. NF-positive tumors had a higher chance of disease-free state, irrespective of histological subgroup (p = 0.0036). The median disease-free survival in pineoblastomas with negative NF staining was 5 months, which was less than that of pineoblastomas with positive NF staining (32 months). Neurofilament immunoreactivity indicates better prognosis in pineal parenchymal tumors. The MIB-1 labeling index can be utilized as an additional tool to differentiate pineal parenchymal tumors into various subgroups.

Series of pinealoblastomas (PB) usually comprise small number of cases as this tumor type is extremely rare and occurs mainly in childhood (especially under 9 years of age). Frequently, PB are reported together with others pineal parenchymal tumors (PPT) or pineal tumors, making characterization far from adequate. Our series of CNS pediatric tumors comprises 1,350 cases of whom 16 are PPT, 12 PB, two pineocytomas (PC), and two mixed or transitional tumors (PC/PB). We have only analyzed the PB considering clinical features, treatment strategy, prognosis, recurrences, and mortality. PB represented 0.89%. Mean age was 7 years. Male-female ratio was 8/4. All patients complained of increased intracranial pressure, eight presented ocular symptoms, two cerebellar, and one endocrine disturbances. Patients underwent CT scans and/or MRI. All children had negative serum and CSF markers and only one case had positive tumor cells in the CSF on admission. Hydrocephalus (12/12) was treated with ventriculoperitoneal shunt in 11/12 and endoscopic third ventriculostomy (ETV) in 1/12. We performed 11 surgical procedures (seven by occipital transtentorial approach) and one endoscopic biopsy. Total removal was achieved in two, partial removal (50-90%) in seven, and biopsy in three patients or <50%. Adjuvant therapy included radiotherapy and chemotherapy. Recurrences appeared in 8/12 cases (mean time of recurrence=27.28 months). Six patients died (mean survival=29.55 months). Mean follow up for the six patients alive was 54 months and mean follow up for all 12 children was 38.7 months. In our opinion, PB have a poor prognosis and are very aggressive, especially in small children. Survival rate at 1 and 5 years in the present series is 66.6% (8/12) and 50% (6/12), respectively. We propose an algorithm for the treatment of pediatric patients with PB.

INTRODUCTION: Pineoblastoma (PB) is one of the rarest and most aggressive brain tumors of childhood. PB is considered a “primitive neuroectodermal tumor” (PNET) based on histology, and commonly treated using treatment protocols developed for medulloblastoma; however the survival remains poor. A subset of PBs may occur in the setting of germline mutations involving DICER1 or RB1, but no next-generation sequencing studies have been published on PB to date, and the genetic drivers of sporadic PB remain unknown. METHODS: 21 tumor samples with a histological diagnosis of PB (including recurrent/metastatic samples) from 15 patients were included in this study. Matching germline DNA was available from 2 patients. We performed genome-wide methylation array profiling (Illumina Infinium 450k) on all samples, as well as whole-genome (for samples with matching germline DNA) or whole-exome sequence analysis. Fluorescence in situ hybridization (FISH) and digital droplet PCR (ddPCR) was performed to confirm select focal somatic gains. RESULTS: 14/18 samples from 9/13 patients analyzed by 450k profiling had a methylation signature similar to previously profiled PBs from a reference cohort. Samples from 4 patients were found to be more consistent with a diagnosis of embryonal tumor with multilayered rosettes (ETMR) - like tumor (non 19q amplified), papillary tumor of the pineal region, or pineal parenchymal tumor of intermediate differentiation, respectively. No mutations in DICER1 or RB1 were found. Homozygous deletions in DROSHA were found in tumors from 3 PB patients. In addition, we identified novel recurrent somatic gains involving chromosomal region 1q21 that were confirmed by FISH and ddPCR in 4/5 PB patients. CONCLUSION: Our studies revealed multiple candidate drivers of oncogenesis in PB. We identified novel homozygous deletions in DROSHA, a nuclease involved in microRNA processing. We also identified novel, highly recurrent somatic focal gains involving chromosomal region 1q21, which has been linked to brain growth, autism and schizophrenia, but not previously associated with cancer. Citation Format: Matija Snuderl, Kasthuri Kannan, Olga Aminova, Igor Dolgalev, Adriana Heguy, Arline Faustin, David Zagzag, Sharon L. Gardner, Jeffrey C. Allen, Jeffrey H. Wisoff, David Capper, Volker Hovestadt, Sama Ahsan, Charles Eberhart, Stefan M. Pfister, David T. w. Jones, Matthias A. Karajannis. Novel candidate oncogenic drivers in pineoblastoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-172. doi:10.1158/1538-7445.AM2015-LB-172

INTRODUCTION: Pineoblastoma (PB) is one of the rarest and most aggressive brain tumors of childhood. PB is considered a “primitive neuroectodermal tumor” (PNET) based on histology, and commonly treated using treatment protocols developed for medulloblastoma. A subset of PBs may occur in the setting of germline mutations involving DICER1, but no next-generation sequencing studies have been published on PB to date, and the genetic drivers of sporadic PB remain unknown. METHODS: 21 tumor samples with a histological diagnosis of PB (including recurrent/metastatic samples) from 15 patients were included in this study. Matching germline DNA was available from 2 patients. We performed genome-wide methylation array profiling (Illumina Infinium 450k) on all samples, as well as whole-genome (for samples with matching germline DNA) or whole-exome sequence analysis. Fluorescence in situ hybridization (FISH) and digital droplet PCR (ddPCR) was performed to confirm select focal somatic gains. RESULTS: 14/18 samples from 9/13 patients analyzed by 450k profiling had a methylation signature similar to previously profiled PBs from a reference cohort. Samples from 4 patients were found to be more consistent with a diagnosis of embryonal tumor with multilayered rosettes (ETMR) - like tumor (non 19q amplified), papillary tumor of the pineal region, or pineal parenchymal tumor of intermediate differentiation, respectively. No mutations in DICER1 or RB1 were found. Homozygous deletions in DROSHA were found in tumors from 3 PB patients. We identified novel and recurrent somatic gains involving chromosomal region 1q21 that were confirmed by FISH and ddPCR in 4/5 PB patients. CONCLUSION: Our studies revealed multiple candidate drivers of oncogenesis in PB. We identified novel homozygous deletions in DROSHA, a nuclease involved in microRNA processing. We also identified novel, highly recurrent somatic focal gains involving chromosomal region 1q21, which has been linked to brain growth, autism and schizophrenia, but not previously associated with cancer.

BackgroundTo evaluate the effectivity of fractionated radiotherapy in adolescent and adult patients with pineal parenchymal tumors (PPT).MethodsBetween 1982 and 2003, 14 patients with PPTs were treated with fractionated radiotherapy. 4 patients had a pineocytoma (PC), one a PPT with intermediate differentiation (PPTID) and 9 patients a pineoblastoma (PB), 2 of which were recurrences. All patients underwent radiotherapy on the primary tumor site with a median total dose of 54 Gy. In 9 patients with primary PB treatment included whole brain irradiation (3 patients) or irradiation of the craniospinal axis (6 patients) with a median total dose of 35 Gy.ResultsMedian follow-up was 123 months in the PC patients and 109 months in the patients with primary PB. 7 patients were free from relapse at the end of follow-up. One PC patient died from spinal seeding. Among 5 PB patients treated with radiotherapy without chemotherapy, 3 developed local or spinal tumor recurrence. Both patients treated for PB recurrences died. The patient with PPTID is free of disease 7 years after radiotherapy.ConclusionLocal radiotherapy seems to be effective in patients with PC and some PPTIDs. Diagnosis and treatment of patients with more aggressive variants of PPTIDs as well as treatment of PB needs to be further improved, since local and spinal failure even despite craniospinal irradiation (CSI) is common. As PPT are very rare tumors, treatment within multi-institutional trials remains necessary.

Simple SummaryPineal region tumors are rare intracranial tumors. A deeper knowledge of these tumors’ molecular mechanisms has been gained in recent years, which has led to a new classification and new potential systemic treatments. Surgery remains the mainstay of treatment, while radiotherapy and systemic therapy depend on histological, molecular, and clinical characteristics. This paper highlights recent developments in the diagnosis and treatment of these tumors.Pineal region tumors are rare intracranial tumors, accounting for less than 1% of all adult intracranial tumor lesions. These lesions represent a histologically heterogeneous group of tumors. Among these tumors, pineal parenchymal tumors and germ cell tumors (GCT) represent the most frequent types of lesions. According to the new WHO 2021 classification, pineal parenchymal tumors include five distinct histotypes: pineocytoma (PC), pineal parenchymal tumors of intermediate differentiation (PPTID), papillary tumor of the pineal region (PTPR), pinealoblastoma (PB), and desmoplastic myxoid tumor of the pineal region, SMARCB1-mutant; GCTs include germinoma, embryonal carcinoma, yolk sac tumor, choriocarcinoma, teratoma, mixed GCTs. Neuroradiological assessment has a pivotal role in the diagnostic work-up, surgical planning, and follow-up of patients with pineal masses. Surgery can represent the mainstay of treatment, ranging from biopsy to gross total resection, yet pineal region tumors associated with obstructive hydrocephalus may be surgically managed via ventricular internal shunt or endoscopic third ventriculostomy. Radiotherapy remains an essential component of the multidisciplinary treatment approach for most pineal region tumors; however, treatment volumes depend on the histological subtypes, grading, extent of disease, and the combination with chemotherapy. For localized germinoma, the current standard of care is chemotherapy followed by reduced-dose whole ventricular irradiation plus a boost to the primary tumor. For pinealoblastoma patients, postoperative radiation has been associated with higher overall survival. For the other pineal tumors, the role of radiotherapy remains poorly studied and it is usually reserved for aggressive (grade 3) or recurrent tumors. The use of systemic treatments mainly depends on histology and prognostic factors such as residual disease and metastases. For pinealoblastoma patients, chemotherapy protocols are based on various alkylating or platinum-based agents, vincristine, etoposide, cyclophosphamide and are used in association with radiotherapy. About GCTs, their chemosensitivity is well known and is based on cisplatin or carboplatin and may include etoposide, cyclophosphamide, or ifosfamide prior to irradiation. Similar regimens containing platinum derivatives are also used for non-germinomatous GCTs with very encouraging results. However, due to a greater understanding of the biology of the disease’s various molecular subtypes, new agents based on targeted therapy are expected in the future. On behalf of the EURACAN domain 10 group, we reviewed the most important and recent developments in histopathological characteristics, neuro-radiological assessments, and treatments for pineal region tumors.

Ovarian Sertoli-Leydig cell tumor (SLCT) with heterologous rhabdomyosarcoma (RMS) is exceptionally rare. While the presence of heterologous elements in SLCT is highly predictive of an underlying DICER1 mutation, the molecular alterations in these tumors, including in SLCTs with heterologous RMS, remain largely unknown. In this study, we aimed to characterize the clinicopathologic features of these rare tumors, and in a subset of cases, we analyzed in detail their molecular changes to investigate potential recurrent and component-specific genetic alterations. We report clinicopathologic features of 11 ovarian SLCTs with heterologous RMS (positivity for desmin and myogenin); 10 were in keeping with embryonal and 1 with pleomorphic RMS. The patients showed a bimodal age distribution: seven patients (64%) were aged 33 years or younger (mean 20) and four patients (36%) were aged 52 years or older (mean 60). All tumors were unilateral. In addition to the RMS components, 8 of 11 cases (73%) contained other heterologous elements, including gastrointestinal-type mucinous epithelium (5 cases) and immature cartilage (3 cases). Seven of 11 cases (64%) underwent next-generation sequencing analysis. All tumors tested molecularly (7/7, 100%) harbored hotspot DICER1 mutations. Of these, six cases (86%) also carried a second nonsense or frameshift loss-of-function DICER1 mutation. One case had only a p.D1810Y hotspot mutation and consisted of high-grade sarcoma with focal rhabdomyoblastic differentiation (focal expression of desmin and myogenin) in keeping with pleomorphic RMS; the pleomorphic sarcoma component also exhibited mutation-type p53 expression. In addition to DICER1 mutations, TERT c.-124C>T promoter (4 cases) or TP53 mutations (3 cases) were present in all cases and were mutually exclusive. Component-specific analysis in two cases revealed shared common DICER1 hotspot mutations in both the SLCT and RMS components, supporting a clonal origin. In 1 case, a TERT promoter c.-124C>T somatic mutation was present only in the RMS component. In the other case, the TERT promoter mutation was found in both components, while a BRAF p.V600E mutation was exclusive to the RMS component. Our study demonstrates that the majority (86%) of SLCTs with heterologous RMS harbor double DICER1 mutations (a hotspot mutation and a nonsense or frameshift loss-of-function mutation), supporting the existing knowledge on DICER1 mutations associated with RMS heterologous elements, the presence of which should trigger genetic counselling. Our findings also suggest that molecular alterations other than DICER1, namely, TERT promoter and TP53 mutations, may contribute to component-specific oncogenic transformation.

The WHO classification of CNS tumors divides pineal parenchymal tumors (PPT) into pineocytoma (PC), pineoblastoma (PB) and mixed pineocytoma-pineoblastoma or PPT with intermediate differentiation. The reported incidence of mixed/intermediate PPT varies and this may reflect the difficulty in classifying tumors of this type. In an attempt to overcome the problem of the classification of PPT with intermediate differentiation, we describe the relationship between histological features and patient survival in a large cooperative series of 66 PPT from 12 neurosurgical centres. All tumors were studied with both light microscopy and immunohistochemically using antibodies against glial markers or neural/neuroendocrine markers. Our series included 11 PC, 39 mixed/intermediate PPT and 16 PB. A number of mitoses greater than 6 and the presence of necrosis were associated with a poorer outcome, while positive immunostaining for neurofilaments was associated with a better survival. We propose a new prognostic grading of 4 grades, grade I for PC, grade II for PPT with fewer than 6 mitoses and positive immunolabelling for neurofilaments, grade III for PPT with either 6 or more than 6 mitoses or fewer than 6 mitoses but without immunostaining for neurofilaments and grade IV for PB.

INTRODUCTION: Pineoblastoma (PB) is one of the rarest and most aggressive brain tumors of childhood. PB is considered a primitive neuroectodermal (PNET) based on histology, and commonly treated using treatment protocols developed for medulloblastoma. A subset of PBs may occur in the setting of germline mutations involving DICER1, but no next-generation sequencing studies have been published on PB to date, and the genetic drivers of sporadic PB remain unknown. METHODS: 21 tumor samples with a histological diagnosis of PB (including recurrent/metastatic samples) from 15 patients were included in this study. Matching germline DNA was available from 2 patients. We performed genome-wide methylation array profiling (Illumina Infinium 450k) on all samples, as well as whole-genome (for samples with matching germline DNA) or whole-exome sequence analysis. Fluorescence in situ hybridization (FISH) and digital droplet PCR (ddPCR) was performed to confirm select focal somatic gains. RESULTS: 14/18 samples from 9/13 patients analyzed by 450k profiling had a methylation signature similar to previously profiled PBs from a reference cohort. Samples from 4 patients were found to be more consistent with a diagnosis of embryonal tumor with multilayered rosettes (ETMR) - like tumor (non 19q amplified), papillary tumor of the pineal region, or pineal parenchymal tumor of intermediate differentiation, respectively. No mutations in DICER1 or RB1 were found. Homozygous deletions in DROSHA were found in tumors from 3 PB patients. We identified novel and recurrent somatic gains involving chromosomal region 1q21 that were confirmed by FISH and ddPCR in 4/5 PB patients. CONCLUSION: Our studies revealed multiple candidate drivers of oncogenesis in PB. We identified novel homozygous deletions in DROSHA, a nuclease involved in microRNA processing. We also identified novel, highly recurrent somatic focal gains involving chromosomal region 1q21, which has been linked to brain growth, autism and schizophrenia, but not previously associated with cancer.

Clinicopathologic Study of Pineal Parenchymal Tumors of Intermediate Differentiation