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ETMR, an aggressive disease characterised by C19MC alterations, were previously categorised as various histologic diagnoses. The clinical spectrum and impact of conventional multi-modal therapy on this new WHO diagnostic category remains poorly understood as a majority of ~200 cases reported to date lack molecular confirmation. We undertook comprehensive clinico-pathologic studies of a large molecularly confirmed cohort to improve disease recognition and treatment approaches. Amongst 623 CNS-PNETs patients enrolled in the RBTC registry, 159 primary ETMRs were confirmed based on a combination of FISH (125), methylation analysis (88), SNP and RNAseq (32) analyses; 91% had C19MC amplification/gains/fusions, 9% lacked C19MC alterations but had global methylation features of ETMR NOS. ETMRs arose in young patients (median age 26 months) predominantly as localized disease (M0-72%, M2-3 -18%) at multiple locations including cerebrum (60%) cerebellum (18%), midline structures (6%); notably 10% were brainstem primaries mimicking DIPG. Uni-and multivariate analyses of clinical and treatment details of curative regimens available for 110 patients identified metastatic disease (p=0.002), brainstem locations(p=0.005), extent of surgery, receipt of multi-modal therapy including high dose chemotherapy and radiation (P

BACKGROUND Choroid plexus tumors (CPT) include choroid plexus papilloma (CPP), atypical choroid plexus papilloma (aCPP), and choroid plexus carcinoma (CPC). Because of their rarity, limited data are available on the current status of treatment and outcomes for pediatric CPTs. METHOD We retrospectively reviewed clinical information on patients with CPT patients aged between 0 and 30 years at diagnosis and were treated in 8 institutions in Japan. RESULTS Of forty-two cases initially diagnosed as CPT, 18 cases were reviewed by central pathologists. As a result, the diagnosis of CPC or aCPP in five cases were changed to other tumors including AT/RT and astroblastoma. The remaining 37 cases were subjected to analysis. Median age at diagnosis was two years (0 to 25) and the mean follow-up period was seven years. All 26 patients with CPP (n=20) or aCPP (n=6) underwent gross-total resection without adjuvant therapy. Of them 24 patients are alive without recurrence. Four patients of patients with CPC (n=11) died of cancer. Five patients including three patients experienced local relapse, achieved complete remission after resection of tumor plus chemoradiotherapy. All three patients with dissemination of CPC at diagnosis or relapse died of the disease. At least three patients were diagnosed with Li-Fraumeni syndrome: one died of medulloblastoma and one patient developed osteosarcoma. CONCLUSION Compared with the excellent prognosis of CPP, the survival rates for CPC, especially disseminated CPC are unsatisfactory. Our results also underline the importance of considering genetic testing of TP53 for patients with CPC.

The most recurrent fusion of CNS high-grade neuroepithelial tumor with MN1alteration(HGNET-MN1) is MN1- BEN Domain Containing 2(BEND2) fusion. Recently, there was a report of a 3-month-old boy with spinal astroblastoma, classified as CNS HGNET-MN1 by DKFZ methylation classification but positive for EWSR1-BEND2 fusion(Yamasaki, 2019). Here, we report a 36-year old man with a spinal cord astroblastoma with EWSR1 alternation. The patient presented with back pain, gait disorder and dysesthesia in lower extremities and trunk was referred to our hospital. MRI showed intramedullary tumor in Th3-5 level, displaying low-intensity on T1 weighted image, high-intensity on T2 weighted image, and homogeneous gadolinium enhancement. Partial removal was performed with the laminectomy. The tumor extended to extramedullary and its boundary was unclear. Histological examinations showed the epithelium-like tumor cells with eosinophilic cytoplasm with high cellularity palisade, intracellar fibrosis, and mitosis. Immunohistochemical staining showed positive for Olig2, GFAP, EMA, SSTR2, S-100, but negative for p53, PgRAE1/AE3. The tumor was diagnosed as astroblastoma, and was classified as HGNET-MN1 by the DKFZ methylation classifier. However, the MN1 alternation was not detected by fluorescence in situ hybridization, instead EWSR1 and BEND2 alternations which suggested EWSR1-BEND2 fusion were detected. After radiation therapy of 54Gy/30fr with bevacizumab and temozolomide, the residual tumor reduced the size and his symptoms improved. This case provides evidence that EWSR1-BEND2 fusion is recurrent in HGNET-MN1 and, as previously reported, suggests the importance of BEND2 in this entity. These two cases suggested that it may be the BEND2 alteration that biologically defines the HGNET-MN1 subclass rather than MN1.

INTRODUCTION Since 2016, the Japan Children’s Cancer Group (JCCG) has established a nationwide network that prospectively provides pathological review and molecular analysis. METHODS Patients who were diagnosed with brain tumors between ages 0 and 29 were eligible. The central office at National Center for Child Health and Development served as a hub for the hospitals involved and institutions conducting pathological and molecular analysis, and managed the patients’ clinical information and tumor samples. Histopathology of all cases were centrally reviewed. Routine non-NGS based analyses were conducted based on histological diagnosis and included pyrosequencing for glioma-associated hot spot mutations and PFA/PFB classification for ependymoma, RT-PCR for RELA fusion and BRAF fusion, and nanostring for subgrouping medulloblastoma. In selected cases, methylation analysis, RNA sequencing and exon sequencing of 93 genes were performed in selected cases. RESULTS In total, 985 cases were registered to this study in four years. Frozen samples were collected from approximately 80% of cases. The number increased from 152 in 2016 to 326 in 2019. They includes glioma (n=268), medulloblastoma (n=161), ependymoma (n=103), germ cell tumor (n=93), ATRT (n=29) and others. In 55 % of the glioma cases, at least one abnormality was detected by the routine analysis. The detailed analysis for atypical cases identified targetable alternations. DISCUSSION: This nationwide central diagnostic system has now been well established. Current issues and future prospective of the system will be discussed.

Molecular tests have now become an essential part of clinical management of pediatric brain tumor patients. We have established a central diagnosis system for pediatric brain tumors in Japan to provide standardized molecular diagnostic service. Tumor specimen are accepted from centers participating Japan Children’s Cancer Group (JCCG). The JCCG Datacenter at National Center for Child Health and Development (NCCHD) manages all patients’ specimen and information. Histology is centrally reviewed at Gunma University Hospital. Molecular tests are performed at either Osaka National Hospital (medulloblastoma), Gunma University Hospital (ETMR) or National Cancer Center (all the others). Medulloblastomas are classified by expression profiling using the nanostring technology, and mutations of CTNNB1, TP53 and TERT determined. Gliomas are examined for mutations of BRAF, H3F3A, HIST1H3B, FGFR1, IDH1/2 and TERT using pyrosequencing, as well as for BRAF fusion by RT-PCR as necessary. Supratentorial ependymomas are examined for the presence of RELA fusion by RT-PCR, and posterior fossa ependymomas are classified as PFA or PFB by DNA methylation analysis. Those tumors negative for the routine analyses may be subjected to RNA sequencing or targeted sequencing for 93 genes known to be mutated in brain tumors. As of August 2017, over 200 tumors have been molecularly diagnosed and the integrated diagnosis reported to each center. Our system is affordable utilizing minimum amount of high throughput technologies, and will hopefully improve the standard of diagnosis for pediatric brain tumors.