Diffusion-weighted imaging does not seem to be a predictor of consistency in pituitary adenomas

PURPOSE

To prospectively evaluate the usefulness of T1-weighted imaging (T1WI) and diffusion-weighted imaging (DWI) sequences in predicting the consistency of macroadenomas. In addition, to determine their values ​​as prognostic factors of surgical outcomes.

METHODS

Patients with pituitary macroadenoma and surgical indication were included. All patients underwent pre-surgical magnetic resonance imaging (MRI) that included the sequences T1WI before and after contrast administration and DWI with the apparent diffusion coefficient (ADC) map. Post-surgical MRI was performed at least 3 months after surgery. The consistency of the macroadenomas was evaluated at surgery, and they were grouped into soft and intermediate/hard adenomas. Mean ADC values, signal on T1WI and the ratio of tumor ADC values ​​to pons (ADCR) were compared with tumor consistency and grade of surgical resection.

RESULTS

A total of 80 patients were included. A softened consistency was found at surgery in 53 patients and hardened in 27 patients. The median ADC in the soft consistency group was 0.532 × 10-3 mm2/sec (0.306 - 1.096 × 10-3 mm2/sec), and in the intermediate/hard consistency group was 0.509 × 10-3 mm2/sec (0.308 - 0.818 × 10-3 mm2/sec). There was no significant difference between the median values ​​of ADC, ADCR and signal on T1W between the soft and hard tumor groups, or between patients with and without tumor residue.

CONCLUSION

Our results did not show usefulness of the DWI and T1WI for assessing the consistency of pituitary macroadenomas, nor as a predictor of the degree of surgical resection.

Molecular and clinicopathologic characteristics of CNS embryonal tumors with BRD4::LEUTX fusion

Central nervous system (CNS) embryonal tumors are a heterogeneous group of high-grade malignancies, and the increasing clinical use of methylation profiling and next-generation sequencing has led to the identification of molecularly distinct subtypes. One proposed tumor type, CNS tumor with BRD4::LEUTX fusion, has been described. As only a few CNS tumors with BRD4::LEUTX fusions have been described, we herein characterize a cohort of 9 such cases (4 new, 5 previously published) to further describe their clinicopathologic and molecular features. We demonstrate that CNS embryonal tumor with BRD4::LEUTX fusion comprises a well-defined methylation class/cluster. We find that patients are young (4 years or younger), with large tumors at variable locations, and frequently with evidence of leptomeningeal/cerebrospinal fluid (CSF) dissemination. Histologically, tumors were highly cellular with high-grade embryonal features. Immunohistochemically, 5/5 cases showed synaptophysin and 4/5 showed OLIG2 expression, thus overlapping with CNS neuroblastoma, FOXR2-activated. DNA copy number profiles were generally flat; however, two tumors had chromosome 1q gains. No recurring genomic changes, besides the presence of the fusion, were found. The LEUTX portion of the fusion transcript was constant in all cases assessed, while the BRD4 portion varied but included a domain with proto-oncogenic activity in all cases. Two patients with clinical follow up available had tumors with excellent response to chemotherapy. Two of our patients were alive without evidence of recurrence or progression after gross total resection and chemotherapy at 16 and 33 months. One patient relapsed, and the last of our four patients died of disease one month after diagnosis. Overall, this case series provides additional evidence for this as a distinct tumor type defined by the presence of a specific fusion as well as a distinct DNA methylation signature. Studies on larger series are required to further characterize these tumors.

Liquid biopsy evaluation of circulating tumor DNA, miRNAs, and cytokines in meningioma patients

Introduction

Liquid biopsy is a non-invasive method used to detect cancer and monitor treatment responses by analyzing blood or other bodily fluids for cancer biomarkers. Meningiomas are the most common primary central nervous system tumors, and biomarkers play a crucial role in their diagnosis, prognosis, and treatment monitoring. The World Health Organization (WHO) classifies meningiomas based on tumor grades and molecular alterations in genes such as in NF2, AKT1, TRAF7, SMO, PIK3CA, KLF4, SMARCE1, BAP1, H3K27me3, TERT promoter, and CDKN2A/B. Liquid biopsy, specifically cell-free DNA (cfDNA) analysis, has shown potential for monitoring meningiomas as it can detect ctDNA release in the blood, unaffected by the blood-brain barrier. MicroRNAs (miRNAs) have also been found to be deregulated in various cancers, including meningiomas, presenting potential as diagnostic biomarkers. Additionally, studying cytokines in the tumor microenvironment may aid in establishing prognostic or diagnostic panels for meningiomas.

Methods

In the present study we analyzed the DNA coming from both the plasma and tumor samples, in addition to analyze miRNA-21 and cytokines in the plasma of 28 meningioma patients.

Discussion and Conclusion

Our findings indicate that the detection of ctDNA in the plasma of meningioma patients is feasible. However, it's important to note that certain challenges persist when comparing plasma DNA analysis to that of tumor tissues. In our study, we observed a paired identification of mutations in only one patient, highlighting the complexities involved. Furthermore, we successfully identified miR-21 and cytokines in the plasma samples. Notably, our analysis of Interleukin 6 (IL-6) unveiled higher expression in the clear cell subtype compared to the other types. Despite the ongoing research, the clinical implementation of liquid biopsy in meningiomas remains somewhat limited. Nevertheless, our promising results underscore the need for further investigation.

p16 Immunohistochemistry as a Screening Tool for Homozygous CDKN2A Deletions in CNS Tumors

The 2021 World Health Organization classification of tumors of the central nervous system emphasizes the significance of molecular parameters for an integrated diagnosis. Homozygous deletion of cyclin-dependent kinase inhibitor 2a (CDKN2A) has been associated with an adverse prognosis in IDH -mutant gliomas, supratentorial ependymomas, meningiomas, and MPNST. In this study, we examined the value of p16 protein immunohistochemistry as a rapid and cost-effective screening tool for a homozygous CDKN2A deletion. Genetic analyses for CDKN2A in 30 pleomorphic xanthoastrocytomas, 32 IDH -wild-type high-grade gliomas, 40 supratentorial ependymomas with ZFTA-RELA gene fusion, 21 IDH-mutant astrocytomas, and 24 meningiomas were performed mainly by a molecular inversion probe assay, a high-resolution, quantitative technology for the assessment of chromosomal copy number alterations. Immunohistochemistry for p16 proved to have a high positive predictive value (range 90% to 100%) and an overall low negative predictive value (range 22% to 93%) for a homozygous CDKN2A deletion. In a setting where molecular testing is limited for cost and time reasons, p16 immunohistochemistry serves as a useful and rapid screening tool for identifying cases that should be subjected to further molecular testing for CDKN2A deletions.

Optimizing biomarkers for accurate ependymoma diagnosis, prognostication, and stratification within International Clinical Trials: A BIOMECA study

BACKGROUND

Accurate identification of brain tumor molecular subgroups is increasingly important. We aimed to establish the most accurate and reproducible ependymoma subgroup biomarker detection techniques, across 147 cases from International Society of Pediatric Oncology (SIOP) Ependymoma II trial participants, enrolled in the pan-European "Biomarkers of Ependymoma in Children and Adolescents (BIOMECA)" study.

METHODS

Across 6 European BIOMECA laboratories, we evaluated epigenetic profiling (DNA methylation array); immunohistochemistry (IHC) for nuclear p65-RELA, H3K27me3, and Tenascin-C; copy number analysis via fluorescent in situ hybridization (FISH) and MLPA (1q, CDKN2A), and MIP and DNA methylation array (genome-wide copy number evaluation); analysis of ZFTA- and YAP1-fusions by RT-PCR and sequencing, Nanostring and break-apart FISH.

RESULTS

DNA Methylation profiling classified 65.3% (n = 96/147) of cases as EPN-PFA and 15% (n = 22/147) as ST-ZFTA fusion-positive. Immunohistochemical loss of H3K27me3 was a reproducible and accurate surrogate marker for EPN-PFA (sensitivity 99%-100% across 3 centers). IHC for p65-RELA, FISH, and RNA-based analyses effectively identified ZFTA- and YAP-fused supratentorial ependymomas. Detection of 1q gain using FISH exhibited only 57% inter-center concordance and low sensitivity and specificity while MIP, MLPA, and DNA methylation-based approaches demonstrated greater accuracy.

CONCLUSIONS

We confirm, in a prospective trial cohort, that H3K27me3 immunohistochemistry is a robust EPN-PFA biomarker. Tenascin-C should be abandoned as a PFA marker. DNA methylation and MIP arrays are effective tools for copy number analysis of 1q gain, 6q, and CDKN2A loss while FISH is inadequate. Fusion detection was successful, but rare novel fusions need more extensive technologies. Finally, we propose test sets to guide future diagnostic approaches.

Case report: Regression of Glioblastoma after flavivirus infection

Glioblastoma is the most frequent and aggressive primary brain cancer. In preclinical studies, Zika virus, a flavivirus that triggers the death of glioblastoma stem-like cells. However, the flavivirus oncolytic activity has not been demonstrated in human patients. Here we report a glioblastoma patient who received the standard of care therapy, including surgical resection, radiotherapy and temozolomide. However, shortly after the tumor mass resection, the patient was clinically diagnosed with a typical arbovirus-like infection, during a Zika virus outbreak in Brazil. Following the infection resolution, the glioblastoma regressed, and no recurrence was observed. This clinical response continues 6 years after the glioblastoma initial diagnosis.

Multiomic neuropathology improves diagnostic accuracy in pediatric neuro-oncology

The large diversity of central nervous system (CNS) tumor types in children and adolescents results in disparate patient outcomes and renders accurate diagnosis challenging. In this study, we prospectively integrated DNA methylation profiling and targeted gene panel sequencing with blinded neuropathological reference diagnostics for a population-based cohort of more than 1,200 newly diagnosed pediatric patients with CNS tumors, to assess their utility in routine neuropathology. We show that the multi-omic integration increased diagnostic accuracy in a substantial proportion of patients through annotation to a refining DNA methylation class (50%), detection of diagnostic or therapeutically relevant genetic alterations (47%) or identification of cancer predisposition syndromes (10%). Discrepant results by neuropathological WHO-based and DNA methylation-based classification (30%) were enriched in histological high-grade gliomas, implicating relevance for current clinical patient management in 5% of all patients. Follow-up (median 2.5 years) suggests improved survival for patients with histological high-grade gliomas displaying lower-grade molecular profiles. These results provide preliminary evidence of the utility of integrating multi-omics in neuropathology for pediatric neuro-oncology.

The Use of Liquid Biopsy in the Molecular Analysis of Plasma Compared to the Tumour Tissue from a Patient with Brain Metastasis: A Case Report

Different cancers have multiple genetic mutations, which vary depending on the affected tumour tissue. Small biopsies may not always represent all the genetic landscape of the tumour. To improve the chances of identifying mutations at different disease stages (early, during the disease course, and refractory stage), liquid biopsies offer an advantage to traditional tissue biopsy. In addition, it is possible to detect mutations related to metastatic events depending on the cancer types analysed as will be discussed in this case report, which describes a patient with brain metastasis and lung cancer that harboured K-RAS mutations both in the brain tumour and in the ctDNA present in the bloodstream.

Characterization of sporadic somatotropinomas with high GIP receptor expression

PURPOSE

To analyze the expression of glucose-dependent insulinotropic polypeptide receptor (GIPR) in somatotropinomas specimens and compare clinical, biochemical, radiological, therapeutic, molecular, and pathological data among those who overexpressed (GIPR +) and those who did not overexpress (GIPR - ) GIPR.

METHODS

Clinical, biochemical, radiological, molecular, and pathological data were collected. GNAS1 sequencing was performed with the Sanger method. Protein expression of somatostatin receptor subtypes 2 and 5 and CAM 5.2 were analyzed by immunohistochemistry. Quantitative real-time PCR was performed to analyze the mRNA expression of GIPR with the TaqMan® method. Positive expression was considered when the fold change (FC) was above 17.2 (GIPR +).

RESULTS

A total of 74 patients (54% female) were included. Eighteen tumors (24%) were GIPR + . Gsp mutation was detected in 30 tumors (40%). GIPR + tumors were more frequently densely granulated adenomas (83% vs 47%, p = 0.028). There was no difference in clinical, biochemical, radiological, therapeutic (surgical cure or response to medical therapy), or other pathological features between GIPR + and GIPR -  tumors. Twenty-eight out of 56 (50%) GIPR -  tumors harbored a gsp mutation, whereas two out of 18 (11%) GIPR + tumors harbored a gsp mutation (p = 0.005).

CONCLUSION

We described, for the first time, that GIPR + and gsp mutations are not mutually exclusive, but gsp mutations are less common in GIPR + tumors. GIPR + and GIPR -  tumors have similar clinical, biochemical, radiological, therapeutic, and pathological features, with the exception of a high frequency of densely granulated adenomas among GIPR + tumors.

The genomic landscape of dysembryoplastic neuroepithelial tumours and a comprehensive analysis of recurrent cases

AIMS

Dysembryoplastic neuroepithelial tumour (DNT) is a glioneuronal tumour that is challenging to diagnose, with a wide spectrum of histological features. Three histopathological patterns have been described: specific DNTs (both the simple form and the complex form) comprising the specific glioneuronal element, and also the non-specific/diffuse form which lacks it, and has unclear phenotype-genotype correlations with numerous differential diagnoses.

METHODS

We used targeted methods (immunohistochemistry, fluorescence in situ hybridisation and targeted sequencing) and large-scale genomic methodologies including DNA methylation profiling to perform an integrative analysis to better characterise a large retrospective cohort of 82 DNTs, enriched for tumours that showed progression on imaging.

RESULTS

We confirmed that specific DNTs are characterised by a single driver event with a high frequency of FGFR1 variants. However, a subset of DNA methylation-confirmed DNTs harbour alternative genomic alterations to FGFR1 duplication/mutation. We also demonstrated that a subset of DNTs sharing the same FGFR1 alterations can show in situ progression. In contrast to the specific forms, "non-specific/diffuse DNTs" corresponded to a heterogeneous molecular group encompassing diverse, newly-described, molecularly distinct entities.

CONCLUSIONS

Specific DNT is a homogeneous group of tumours sharing characteristics of paediatric low-grade gliomas: a quiet genome with a recurrent genomic alteration in the RAS-MAPK signalling pathway, a distinct DNA methylation profile and a good prognosis but showing progression in some cases. The "non-specific/diffuse DNTs" subgroup encompasses various recently described histomolecular entities, such as PLNTY and diffuse astrocytoma, MYB or MYBL1 altered.

EPEN-24. Biological markers of ependymoma in children and adolescents (BIOMECA): Systematic comparison of methods for the precise evaluation of biomarkers for ependymoma diagnosis and prognostication

The identification and validation of prognostic and diagnostic biomarkers is a key element of The SIOP Ependymoma II trial, realised through the Biomarkers of Ependymoma in Children and Adolescents study (BIOMECA). BIOMECA aims to identify and validate biomarkers for prediction of outcome whilst enhancing stratification for the next generation of ependymoma trials. We outline our findings from the first 147 consecutive BIOMECA cases (posterior fossa, PF=111; supratentorial, ST=32; spinal, SP=4). We compared various methods for biomarker assessment, across six European laboratories to determine key analysis methods. Methods included: methylation-based classification (EPIC 850K DNA methylation array) (n=141); immunohistochemistry (IHC) for nuclear p65-RELA (n=32), H3K27me3 (n=115), and Tenascin-C (TNC) (n=147); copy number (CN) analysis by FISH, MLPA (1q, CDKN2A) (n=147), and MIP (molecular inversion probe) and DNA methylation array (1q, CDKN2A, 6q, 11q, 13q, 22q) (n=141); analysis of ZFTA- and YAP1-fusions by RT-PCR, sequencing, Nanostring assays and break-apart FISH (n=32). Using DNA methylation-based classification, 91% (n=101/111) of PF cases classified as PF ependymoma group A (PFA) and 69% (n=22/32) of ST cases as ST ependymoma, ZFTA fusion-positive (ZFTA). Most PFAs demonstrated inter-centre agreement for loss of H3K27me3, and were TNC positive, representing surrogate markers for PFA identification. Combinations of p65-RELA IHC, FISH analysis, and RNA-based methods were suitable to identify ZFTA- and YAP1- fused ST ependymomas. Predictive CN alterations were identified by high-resolution, quantitative MIP technology.The integration of histopathology assessment and molecular typing is now critical as the updated 2021 WHO CNS5 classification of ependymomas lists seven molecularly distinct entities. This study highlights the importance of evaluating different methods in a prospective trial cohort. Here, advanced molecular techniques represent powerful tools for the classification of ependymoma entities (DNA methylation array) and for the detection of CN alterations (MIP) and specific fusions, enabling the correct classification and identification of prognostic markers.

HGG-59. Pediatric high-grade gliomas and the WHO classification on CNS Tumors - Different perspectives of pediatric neuro-oncologists and neuropathologists in the light of recent updates

BACKGROUND: The WHO Classification of Tumors of the Central Nervous System has undergone major restructuring following rapid advances in brain tumor genomics and epigenomics. The most significant changes resulted from the introduction of molecularly defined diagnostic criteria in 2016 (revised 4th edition). In 2021 (5th edition), further essential molecular criteria were incorporated. In the present study, we sought to investigate potential differences between specialists in perception of these newly defined molecular subtypes of pediatric high-grade gliomas (pedHGG). METHODS: We designed a 22-question survey studying the impact of the revised 4th edition of the WHO classification on pedHGG. Data were collected and statistically analyzed to capture the spectrum of viewpoints and possible differences among neuro-oncologists and neuropathologists. RESULTS: 465 participants from 53 countries responded, of which 187 pediatric neuro-oncologists (40%), 160 neuropathologists (34%) and 118 experts in other related fields (neurosurgeons, radiotherapists, neuroradiologists and others; 26%). Neuro-oncologists reported having issues with the introduction of new molecular entities, such as the abolishment and renaming of established tumor entities. Neuropathologists did not define these problems to the same extent. However, both groups felt that in the 2016 version, less relevant or insufficient diagnostic definitions were available for pedHGG. Within the 2021 WHO classification, a substantial improvement was perceived regarding the definition of pedHGG entities. However, some issues of high clinical relevance, like the definition of clinical phenotypes such as diffuse intrinsic pontine glioma (DIPG) and gliomatosis cerebri, are yet to be addressed. CONCLUSIONS: Within the WHO classification of pediatric brain tumors, such as high-grade gliomas, rapid changes in nomenclature have been introduced because of substantial improvement in molecular characterization. This study highlights that ongoing cross-talk between advancing classification of pedHGG subtypes and its biological relevance and clinical impact is essential.

Pediatric high-grade gliomas and the WHO CNS Tumor Classification—Perspectives of pediatric neuro-oncologists and neuropathologists in light of recent updates

Background

The WHO Classification of Tumors of the Central Nervous System has undergone major restructuring. Molecularly defined diagnostic criteria were introduced in 2016 (revised 4th edition) and expanded in 2021 (5th edition) to incorporate further essential diagnostic molecular parameters. We investigated potential differences between specialists in perception of these molecularly defined subtypes for pediatric high-grade gliomas (pedHGG).

Methods

We designed a 22-question survey studying the impact of the revised 4th edition of the WHO classification on pedHGG. Data were collected and statistically analyzed to examine the spectrum of viewpoints and possible differences between neuro-oncologists and neuropathologists.

Results

465 participants from 53 countries were included; 187 pediatric neuro-oncologists (40%), 160 neuropathologists (34%), and 118 additional experts (26%). Neuro-oncologists reported issues with the introduction of molecularly defined tumor types, as well as the abolishment or renaming of established tumor entities, while neuropathologists did not to the same extent. Both groups indicated less relevant or insufficient diagnostic definitions were available in 2016. Reported issues were classified and assessed in the 2021 WHO classification and a substantial improvement was perceived. However, issues of high clinical relevance remain to be addressed, including the definition of clinical phenotypes for diffuse intrinsic pontine glioma and gliomatosis cerebri.

Conclusions

Within the WHO classification of pediatric brain tumors, such as pedHGG, rapid changes in molecular characterization have been introduced. This study highlights the ongoing need for cross talk between pathologist and oncologist to advance the classification of pedHGG subtypes and ensure biological relevance and clinical impact.

EPCO-03. GLIOMA ONCOGENESIS IN THE CONSTITUTIONAL MISMATCH REPAIR DEFICIENCY (CMMRD) SYNDROME

PURPOSE

Constitutional Mismatch Repair Deficiency (CMMRD) is a cancer predisposition due to bi-allelic mutations in one of the four main mismatch repair (MMR) genes (PMS2, MSH2, MSH6 or MLH1) associated with early onset of cancers, especially glioblastomas (GBM). Our aim was to decipher the molecular specificities of gliomas occurring in this context.

METHODS

A comprehensive analysis of clinical, histopathological and genomic data (whole exome sequencing) was performed for 12 children with a CMMRD for which we had available frozen brain tumor material (10 GBM and 2 anaplastic astrocytomas).

RESULTS

Eight patients harbored an ultra-mutated phenotype with more than 100 somatic non synonymous (NS) SNV/Mb. No correlation was observed between the number of mutation and sex, age, overall survival or mutated MMR gene. POLE and POLD1 exonuclease domain driver somatic mutations were described for eight and one patients respectively. The 4/12 tumors without POLE somatic mutation did not show the classical ultra-hypermutation pattern. All patients with POLE mutation had already more than 20 NS SNV/Mb (median 40NS SNV/Mb, [range 23-114]) suggesting that the hypermutation phenomenon started before the appearance of the somatic POLE mutation. The mutational signatures of the tumors, dominated by the MMR signatures, were not modified after the onset of the POLE mutation when analyzing the different mutation bursts. Specific recurrent somatic mutations were observed in SETD2 (9/12), TP53 (9/12), NF1 (9/12), EPHB2 (8/12), and DICER1 (7/12). Only half of the tumors overexpressed PDL1 by immunohistochemistry and this overexpression was not associated with a higher tumor mutation burden.

CONCLUSION

CMMRD-associated gliomas have a specific oncogenesis that does not trigger usual pathways and mutations seen in sporadic pediatric or adult GBM. Frequent alterations in other pathways (e.g. MAPK or DNA-PK pathway) may suggests the use of other targeted therapies aside from PD1 inhibitors.

Transitioning to molecular diagnostics in pediatric high-grade glioma: experiences with the 2016 WHO classification of CNS tumors

Background

Pediatric neuro-oncology was profoundly changed in the wake of the 2016 revision of the WHO Classification of Tumors of the Central Nervous System. Practitioners were challenged to quickly adapt to a system of tumor classification redefined by molecular diagnostics.

Methods

We designed a 22-question survey studying the impact of the revised WHO classification on pediatric high-grade glioma. The survey collected basic demographics, general attitudes, issues encountered, and opinions on pediatric subtypes. Participant answers were analyzed along socioeconomic lines utilizing the human development index (HDI) of the United Nations and membership in the group of seven (G7) world economic forum.

Results

Four hundred and sixty-five participants from 53 countries were included, 187 pediatric neurooncologists (40%), 160 neuropathologists (34%), and 118 other experts (26%). When asked about pediatric high-grade glioma entities, participants from very high development countries preferred treating a patient based on genetic findings. Participants from high and medium development countries indicated using traditional histology and tumor location as mainstays for therapeutic decisions. Non-G7 countries tended to regard the introduction of molecularly characterized tumor entities as a problem for daily routine due to lack of resources.

Conclusions

Our findings demonstrate an overall greater reliance and favorability to molecular diagnostics among very high development countries. A disparity in resources and access to molecular diagnostics has left some centers unable to classify pediatric high-grade glioma per the WHO classification. The forthcoming edition should strain to abate disparities in molecular diagnostic availability and work toward universal adaptation.

Identification of mutant K-RAS in pituitary macroadenoma

PURPOSE

RAS genes are among the most frequently mutated genes in cancer, where their mutation frequency varies according to the distinct RAS isoforms and tumour types. Despite occurring more prevalent in malignant tumours, RAS mutations were also observed in few benign tumours. Pituitary adenomas are examples of benign tumours which vary in size and aggressiveness. The present study was performed to investigate, via liquid biopsy and tissue analysis, the presence of K-RAS mutations in a pituitary macroadenoma.

METHODS

Molecular analysis was performed to investigate K-RAS mutations using the droplet digital PCR (ddPCR) method by evaluating both plasma (liquid biopsy) and the solid tumour of a patient diagnosed with a giant clinically non-functioning pituitary tumour.

RESULTS

The patient underwent surgical resection due to visual loss, and the histopathological analysis showed a gonadotrophic pituitary macroadenoma. The molecular analysis revealed the presence of mutant K-RAS both in the plasma and in the tumour tissue which, to our knowledge, has not been previously reported in the literature.

CONCLUSION

Our findings highlight the exceptional capacity of the digital PCR in detecting low frequency mutations (below 1%), since we detected, for the first time, K-RAS mutations in pituitary macroadenoma. The potential impact of K-RAS mutations in these tumours should be further investigated.

Supratentorial non-RELA, ZFTA-fused ependymomas: a comprehensive phenotype genotype correlation highlighting the number of zinc fingers in ZFTA-NCOA1/2 fusions

The cIMPACT-NOW Update 7 has replaced the WHO nosology of “ependymoma, RELA fusion positive” by “Supratentorial-ependymoma, C11orf95-fusion positive”. This modification reinforces the idea that supratentorial-ependymomas exhibiting fusion that implicates the C11orf95 (now called ZFTA) gene with or without the RELA gene, represent the same histomolecular entity. A hot off the press molecular study has identified distinct clusters of the DNA methylation class of ZFTA fusion-positive tumors. Interestingly, clusters 2 and 4 comprised tumors of different morphologies, with various ZFTA fusions without involvement of RELA. In this paper, we present a detailed series of thirteen cases of non-RELA ZFTA-fused supratentorial tumors with extensive clinical, radiological, histopathological, immunohistochemical, genetic and epigenetic (DNA methylation profiling) characterization. Contrary to the age of onset and MRI aspects similar to RELA fusion-positive EPN, we noted significant histopathological heterogeneity (pleomorphic xanthoastrocytoma-like, astroblastoma-like, ependymoma-like, and even sarcoma-like patterns) in this cohort. Immunophenotypically, these NFκB immunonegative tumors expressed GFAP variably, but EMA constantly and L1CAM frequently. Different gene partners were fused with ZFTA: NCOA1/2, MAML2 and for the first time MN1. These tumors had epigenetic homologies within the DNA methylation class of ependymomas-RELA and were classified as satellite clusters 2 and 4. Cluster 2 (n = 9) corresponded to tumors with classic ependymal histological features (n = 4) but also had astroblastic features (n = 5). Various types of ZFTA fusions were associated with cluster 2, but as in the original report, ZFTA:MAML2 fusion was frequent. Cluster 4 was enriched with sarcoma-like tumors. Moreover, we reported a novel anatomy of three ZFTA:NCOA1/2 fusions with only 1 ZFTA zinc finger domain in the putative fusion protein, whereas all previously reported non-RELA ZFTA fusions have 4 ZFTA zinc fingers. All three cases presented a sarcoma-like morphology. This genotype/phenotype association requires further studies for confirmation. Our series is the first to extensively characterize this new subset of supratentorial ZFTA-fused ependymomas and highlights the usefulness of ZFTA FISH analysis to confirm the existence of a rearrangement without RELA abnormality.

USP8 Somatic Mutations in Cushing’s Disease and Silent Corticotropinomas

Background: Somatic mutations in the ubiquitin-specific peptidase 8 (USP8) gene have been described in Cushing’s disease (CD). These mutations increase proopiomelanocortin transcription resulting in ACTH production and seem to correlate with somatostatin receptor type 5 (SST5) expression. Aims: Screen USP8 in patients with corticotropinomas and correlate USP8 mutational status with SST5 expression in CD. Methods: Tumor DNA was extracted and then exon 14 amplified by PCR. SST5 was assessed by immunohistochemistry (clone UMB4) and quantified multiplying the percentage of positive cells (0,0%; <10%,1;10-50%, 2; 51-80%, 3; >80%, 4) and intensity (mild, 1; moderate, 2; intense, 3), giving a score (IRS) from 0-12 with ≥ 6 considered high. Results: Among 59 patients, 38 had CD and 21 silent corticotropinomas. In CD, 13 (34.2%) patients had pathogenic mutations (6 had p.Ser719del; 5 had p.Pro720Arg and 2 had p.Pro720Gln). In the mutated CD group, all were women and had median age of 34.5 years (20-46). Median ACTH was 64.7pg/mL [(34.8-330.0), normal <46], urinary free cortisol (UFC) 435.0μg/24h [(87.0-1386.0), normal <100], cortisol after overnight 1mg dexamethasone suppression test (ODST) 17.4μg/dL [(5.0-48.7), normal <1.8], salivary cortisol (SC) 8.1μg/dL [(1.0-15.5), normal <0.35]. Median largest tumor size was 0.9 cm (0-1.9), ki-67 1.7 (0.2-10.0) and IRS 12 (1-12). In wild-type CD group, 19 (76.0%) were women and had median age was 35.0 years old (14-62). Median ACTH was 59.7 (39.0-137.0), UFC 305.8 (77.0-1302.0), cortisol after ODST 23.6 (10.0-33.3), SC 0.67 (0.27-1.28). Median largest tumor diameter 0.7cm (0-3.3), ki-67 1.8 (0.2-10) and IRS 4 (0-12). SC was higher in mutated group compared to wild-type (p=0.001) as well as IRS (p=0.009). In silent corticotropinomas, 2 (9.5%) had pathogenic mutations (1 p.Ser718Pro and 1 p.Pro720Arg): male, 36 years old, 3.2 cm tumor, Ki-67 4%, IRS 6; and female, 52 years old, 3.4 cm tumor, Ki-67 2.5%, IRS 12, respectively. One tumor had a variant not reported as pathogenic (p.Thr739Ala): male, 46 years old, 3.7 cm tumor, Ki-67 0.5%, IRS 0. USP8-wild-type silent corticotropinomas had IRS 0-2. Conclusion: One third of CD patients presented with somatic USP8 mutation. Similar to another study, about 10% of silent corticotropinomas also presented somatic USP8 mutation. Expression of SST5 was high in USP8-mutated CD and higher than wild-type group.

Role of neoadjuvant chemotherapy in metastatic medulloblastoma: a comparative study in 92 children

BACKGROUND

Previous pilot studies have shown the feasibility of preoperative chemotherapy in patients with medulloblastoma, but benefits and risks compared with initial surgery have not been assessed.

METHODS

Two therapeutic strategies were retrospectively compared in 92 patients with metastatic medulloblastoma treated at Gustave Roussy between 2002 and 2015: surgery at diagnosis (n = 54, group A) and surgery delayed after carboplatin and etoposide-based neoadjuvant therapy (n = 38, group B). Treatment strategies were similar in both groups.

RESULTS

The rate of complete tumor excision was significantly higher in group B than in group A (93.3% vs 57.4%, P = 0.0013). Postoperative complications, chemotherapy-associated side effects, and local progressions were not increased in group B. Neoadjuvant chemotherapy led to a decrease in the primary tumor size in all patients; meanwhile 4/38 patients experienced a distant progression. The histological review of 19 matched tumor pairs (before and after chemotherapy) showed that proliferation was reduced and histological diagnosis feasible and accurate even after neoadjuvant chemotherapy. The 5-year progression-free and overall survival rates were comparable between groups. Comparison of the longitudinal neuropsychological data showed that intellectual outcome tended to be better in group B (the mean predicted intellectual quotient value was 6 points higher throughout the follow-up).

CONCLUSION

Preoperative chemotherapy is a safe and efficient strategy for metastatic medulloblastoma. It increases the rate of complete tumor excision and may improve the neuropsychological outcome without jeopardizing survival.

KEY POINTS

1. Preoperative chemotherapy increases the rate of complete tumor removal.2. No additional risk (toxic or disease progression) is linked to the delayed surgery.3. Preoperative chemotherapy could have a positive impact on the neuropsychological outcome of patients.

MBCL-02. ROLE OF PREOPERATIVE CHEMOTHERAPY IN METASTATIC MEDULLOBLASTOMA: A COMPARATIVE STUDY IN 92 CHILDREN

BACKGROUND

Previous pilot studies have shown the feasibility of preoperative chemotherapy in patients with medulloblastoma, but benefits and risks compared with initial surgery have not been assessed.

METHODS

Two therapeutic strategies were retrospectively compared in 92 patients with metastatic medulloblastoma treated at Gustave Roussy, France, between 2002 and 2015: surgery at diagnosis (n=54; group A) and surgery delayed after carboplatin and etoposide-based preoperative therapy (n=38; group B). Treatment strategies were similar in both groups.

RESULTS

The rate of complete tumor excision was significantly higher in group B than in group A (93.3% versus 57.4%, p=0.0013). Post-operative complications, chemotherapy-associated side effects and local progressions were not increased in group B. Preoperative chemotherapy led to a decrease in the primary tumor size in all patients, 4/38 patients experiencing meanwhile a distant progression. The histological review of 19 matched tumor pairs (before and after chemotherapy) showed that proliferation was reduced and histological diagnosis feasible and accurate even after preoperative chemotherapy. The 5-year progression-free and overall survival rates were comparable between groups. Comparison of the longitudinal neuropsychological data showed that intellectual outcome tended to be better in group B (the mean predicted intellectual quotient value was 6 points higher throughout the follow-up).

CONCLUSION

Preoperative chemotherapy is a safe and efficient strategy for metastatic medulloblastoma. It increases the rate of complete tumor excision and may improve the neuropsychological outcome without jeopardizing survival.

PATH-11. PROSPECTIVE (EPI-)GENETIC CLASSIFICATION OF &gt; 1,000 PEDIATRIC CNS TUMORS—THE MNP 2.0 STUDY

The large variety of CNS tumor entities affecting children and adolescents, some of which are exceedingly rare, results in very diverging patient outcomes and renders accurate diagnosis challenging. To assess the diagnostic utility of routine DNA methylation-based CNS tumor classification and gene panel sequencing, the Molecular Neuropathology 2.0 study prospectively integrated these (epi-)genetic analyses with reference neuropathological diagnostics as an international trial for newly-diagnosed pediatric patients. In a four-year period, 1,215 patients with sufficient tissue were enrolled from 65 centers, receiving a reference neuropathological diagnosis according to the WHO classification in >97%. Using 10 FFPE sections as input, DNA methylation analysis was successfully performed in 95% of cases, of which 78% with sufficient tumor cell content were assigned to a distinct epigenetic tumor class. The remaining 22% did not match any of 82 represented classes, indicating novel rare tumor entities. Targeted gene panel sequencing of >130 genes performed for 96% of patients with matched blood samples detected diagnostically, prognostically, or therapeutically relevant somatic alterations in 48%. Germline DNA sequencing data indicated potential predisposition syndromes in ~10% of patients. Discrepant results by neuropathological and epigenetic classification (29%) were enriched in histological high-grade gliomas and implicated clinical relevance in 5% of all cases. Clinical follow-up suggests improved survival for some patients with high-grade glioma histology and lower-grade molecular profiles. Routine (epi-)genetic profiling at the time of primary diagnosis adds a valuable layer of information to neuropathological diagnostics and will improve clinical management of CNS tumors.

Infant High-Grade Gliomas Comprise Multiple Subgroups Characterized by Novel Targetable Gene Fusions and Favorable Outcomes

Infant high-grade gliomas appear clinically distinct from their counterparts in older children, indicating that histopathologic grading may not accurately reflect the biology of these tumors. We have collected 241 cases under 4 years of age, and carried out histologic review, methylation profiling, and custom panel, genome, or exome sequencing. After excluding tumors representing other established entities or subgroups, we identified 130 cases to be part of an "intrinsic" spectrum of disease specific to the infant population. These included those with targetable MAPK alterations, and a large proportion of remaining cases harboring gene fusions targeting ALK (n = 31), NTRK1/2/3 (n = 21), ROS1 (n = 9), and MET (n = 4) as their driving alterations, with evidence of efficacy of targeted agents in the clinic. These data strongly support the concept that infant gliomas require a change in diagnostic practice and management. SIGNIFICANCE: Infant high-grade gliomas in the cerebral hemispheres comprise novel subgroups, with a prevalence of ALK, NTRK1/2/3, ROS1, or MET gene fusions. Kinase fusion-positive tumors have better outcome and respond to targeted therapy clinically. Other subgroups have poor outcome, with fusion-negative cases possibly representing an epigenetically driven pluripotent stem cell phenotype.See related commentary by Szulzewsky and Cimino, p. 904.This article is highlighted in the In This Issue feature, p. 890.

YAP1/TAZ drives ependymoma-like tumour formation in mice

YAP1 gene fusions have been observed in a subset of paediatric ependymomas. Here we show that, ectopic expression of active nuclear YAP1 (nlsYAP5SA) in ventricular zone neural progenitor cells using conditionally-induced NEX/NeuroD6-Cre is sufficient to drive brain tumour formation in mice. Neuronal differentiation is inhibited in the hippocampus. Deletion of YAP1's negative regulators LATS1 and LATS2 kinases in NEX-Cre lineage in double conditional knockout mice also generates similar tumours, which are rescued by deletion of YAP1 and its paralog TAZ. YAP1/TAZ-induced mouse tumours display molecular and ultrastructural characteristics of human ependymoma. RNA sequencing and quantitative proteomics of mouse tumours demonstrate similarities to YAP1-fusion induced supratentorial ependymoma. Finally, we find that transcriptional cofactor HOPX is upregulated in mouse models and in human YAP1-fusion induced ependymoma, supporting their similarity. Our results show that uncontrolled YAP1/TAZ activity in neuronal precursor cells leads to ependymoma-like tumours in mice.

WHO grade has no prognostic value in the pediatric high-grade glioma included in the HERBY trial

BACKGROUND

The World Health Organization (WHO) adult glioma grading system is questionable in pediatric high-grade gliomas (pHGGs), which are biologically distinct from adult HGGs. We took advantage of the neuropathological review data obtained during one of the largest prospective randomized pHGG trials, namely HERBY (NCT01390948), to address this issue in children with newly diagnosed non-brainstem HGG.

METHODS

HGG diagnosis was confirmed by pre-randomization, real-time central pathology review using WHO 2007 criteria, followed by a consensus review blinded to clinical factors and outcomes. We evaluated association between WHO 2007 grade and other clinical/radiological/biological characteristics and the prognostic value of WHO 2007 grade, midline location, and selected biomarkers (Ki-67 index/Olig2/CD34/EGFR/p53/H3F3A K27M mutation) on overall survival.

RESULTS

Real-time central neuropathological review was feasible in a multicenter study, with a mean time of 2.4 days, and led to the rejection of HGG diagnosis in 20 of 163 cases (12.3%). The different grading criteria and resulting WHO grade were not significantly associated with overall survival in the entire population (n = 118) or in midline and non-midline subgroups. H3F3A K27M mutation was significantly associated with poor outcome. No significant prognostic value was observed for grade, even after regrading H3F3A K27M-mutated midline glioma as grade IV (WHO 2016). Midline location and a high Ki-67 index (≥20%) were associated with poor outcome (P = 0.004 and P = 0.04, respectively). A 10% increase in Ki-67 index was associated with a hazard ratio of 1.53 (95% CI: 1.27-1.83; P < 0.0001).

CONCLUSION

Our findings suggest that WHO grade III versus IV has no prognostic value in pediatric HGG.

Ependymomas in infancy: underlying genetic alterations, histological features, and clinical outcome

INTRODUCTION

Young age is an adverse prognostic factor in children with ependymomas. Treatment of these infants is challenging since beneficial therapeutic options are limited. As ependymomas are considered a biologically heterogeneous group, we aimed to characterize infant ependymomas with regard to their histological and genetic features.

MATERIALS AND METHODS

We analyzed 28 ependymomas occurring in children younger than 18 months at diagnosis enrolled into the HIT2000-E protocols with the aim to postpone irradiation until the age of 18 months if possible. All cases underwent neuropathological review, including immunohistochemical characterization. Genome-wide copy number alterations (CNA) were assessed by molecular inversion probe assays, and RELA and YAP1 fusions were detected by RT-PCR and sequencing.

RESULTS

All infant ependymomas were anaplastic (WHO grade III). Twenty-one (75%) cases were located in the posterior fossa. Gross total resection was accomplished in 12 (57%) of these cases. All posterior fossa tumors showed loss of H3-K27me³ characteristic of PFA ependymomas. CNA analysis showed a stable genome in all cases with lack of chromosome 1q gain, an adverse prognostic marker in PFA ependymomas of older children. However, after a median follow-up of 5.4 years, 15 (71%) relapsed, and 9 (43%) died. Seven ependymomas (25%) occurred in the supratentorial region. Gross total resection could be achieved in only two of these cases. Four tumors carried C11orf95-RELA fusions, and two cases had typical YAP1-MAMLD1 fusions (one case was not analyzable). The RELA-fused cases did not display CDKN2A loss as an adverse indicator of prognosis in this disease entity. Although three infants (43%) with supratentorial ependymomas relapsed, all patients survived (median follow-up, 8.0 years).

CONCLUSION

Infant ependymomas seem to fall into three biological entities, with supratentorial tumors carrying RELA or YAP fusions and PFA posterior fossa ependymomas. The latter showed a poor outcome even though chromosome 1q gain was absent.

Constitutional mismatch repair deficiency-associated brain tumors: report from the European C4CMMRD consortium

Background

Malignant brain tumors (BT) are among the cancers most frequently associated with constitutional mismatch repair deficiency (CMMRD), a rare childhood cancer predisposition syndrome resulting from biallelic germline mutations in mismatch repair genes. This study analyzed data from the European “Care for CMMRD” (C4CMMRD) database to describe their clinical characteristics, treatments, and outcome with the aim of improving its diagnosis/treatment.

Methods

Retrospective analysis of data on patients with CMMRD and malignant BT from the C4CMMRD database up to July 2017.

Results

Among the 87 registered patients, 49 developed 56 malignant BTs: 50 high-grade gliomas (HGG) (with giant multinucleated cells in 16/21 histologically reviewed tumors) and 6 embryonal tumors. The median age at first BT was 9.2 years [1.1–40.6], with nine patients older than 18. Twenty-seven patients developed multiple malignancies (including16 before the BT). Most patients received standard treatment, and eight patients immunotherapy for relapsed HGG. The 3- and 5-year overall survival (OS) rates were 30% (95% CI: 19–45) and 22% (95% CI: 12–37) after the first BT, with worse prognosis for HGG (3-year OS = 20.5%). Six patients were alive (median follow-up 2.5 years) and 43 dead (38 deaths, 88%, were BT-related). Other CMMRD-specific features were café-au-lait macules (40/41), multiple BTs (5/15), developmental brain anomalies (11/15), and consanguinity (20/38 families).

Conclusions

Several characteristics could help suspecting CMMRD in pediatric malignant BTs: giant cells on histology, previous malignancies, parental consanguinity, café-au-lait macules, multiple BTs, and developmental brain anomalies. The prognosis of CMMRD-associated BT treated with standard therapies is poor requiring new therapeutic up-front approaches.

YAP1 subgroup supratentorial ependymoma requires TEAD and nuclear factor I-mediated transcriptional programmes for tumorigenesis

YAP1 fusion-positive supratentorial ependymomas predominantly occur in infants, but the molecular mechanisms of oncogenesis are unknown. Here we show YAP1-MAMLD1 fusions are sufficient to drive malignant transformation in mice, and the resulting tumors share histo-molecular characteristics of human ependymomas. Nuclear localization of YAP1-MAMLD1 protein is mediated by MAMLD1 and independent of YAP1-Ser127 phosphorylation. Chromatin immunoprecipitation-sequencing analyses of human YAP1-MAMLD1-positive ependymoma reveal enrichment of NFI and TEAD transcription factor binding site motifs in YAP1-bound regulatory elements, suggesting a role for these transcription factors in YAP1-MAMLD1-driven tumorigenesis. Mutation of the TEAD binding site in the YAP1 fusion or repression of NFI targets prevents tumor induction in mice. Together, these results demonstrate that the YAP1-MAMLD1 fusion functions as an oncogenic driver of ependymoma through recruitment of TEADs and NFIs, indicating a rationale for preclinical studies to block the interaction between YAP1 fusions and NFI and TEAD transcription factors.

The molecular mechanisms driving proliferation in the pediatric brain cancer epdendymoma are poorly understood. Here the authors show that a YAP1- MAMLD1 fusion drives tumor formation in mice and show that the fusion protein can collaborate with the TEAD and NFI transcription factors.

Diagnostics of pediatric supratentorial RELA ependymomas: integration of information from histopathology, genetics, DNA methylation and imaging

Ependymoma with RELA fusion has been defined as a novel entity of the revised World Health Organization 2016 classification of tumors of the central nervous system (CNS), characterized by fusion transcripts of the RELA gene and consequent pathological activation of the NFkB pathway. These tumors represent the majority of supratentorial ependymomas in children. The validation of diagnostic tools to identify this clinically relevant ependymoma entity is essential. Here, we have used interphase fluorescent in situ hybridization (FISH) for C11orf95 and RELA, immunohistochemistry (IHC) for p65‐RelA and the recently developed DNA methylation‐based classification besides conventional histopathology, and compared the precision of the methods in 40 supratentorial pediatric brain tumors diagnosed as ependymomas in the past years. Reverse transcription PCR (RT‐PCR) and RNA sequencing were performed to explore discordant cases. Furthermore, we integrated imaging and clinical features as additional layers of information. The concordance between nuclear RelA expression by IHC and RELA FISH was 100%. Concordance between IHC and DNA methylation profiling, and between FISH and DNA methylation profiling was also high (96.4% and 95.2%, respectively). Thirty‐four out of 40 (85%) cases were confirmed by integrated diagnoses as ependymal tumors, including 22 RELA‐fused ependymomas (71% of ependymal tumors), two YAP1‐fused ependymomas (6%), six non‐RELA/non‐YAP1 ependymomas (18%) and four ependymal/subependymal mixed tumors (12%). Ependymal/subependymal mixed tumors had an excellent clinical outcome despite the presence of histopathological signs of malignancy, suggesting that these tumors should not be diagnosed as classic ependymomas. DNA methylation profiling helped in the differential diagnosis of RELA‐fused ependymomas. IHC and FISH, which are available in the majority of pathology laboratories, are valuable tools to identify RELA‐fused ependymomas.

Childhood supratentorial ependymomas with YAP1-MAMLD1 fusion: an entity with characteristic clinical, radiological, cytogenetic and histopathological features

Ependymoma with YAP1‐MAMLD1 fusion is a rare, recently described supratentorial neoplasm of childhood, with few cases published so far. We report on 15 pediatric patients with ependymomas carrying YAP1‐MAMLD1 fusions, with their characteristic histopathology, immunophenotype and molecular/cytogenetic, radiological and clinical features. The YAP1‐MAMLD1 fusion was documented by RT‐PCR/Sanger sequencing, and tumor genomes were studied by molecular inversion probe (MIP) analysis. Significant copy number alterations were identified by GISTIC (Genomic Identification of Significant Targets in Cancer) analysis. All cases showed similar histopathological features including areas of high cellularity, presence of perivascular pseudo‐rosettes, small to medium‐sized nuclei with characteristic granular chromatin and strikingly abundant cells with dot‐like cytoplasmic expression of epithelial membrane antigen. Eleven cases presented features of anaplasia, corresponding to WHO grade III. MRI showed large supratentorial multinodular tumors with cystic components, heterogeneous contrast enhancement, located in the ventricular or periventricular region. One of two variants of YAP1‐MAMLD1 fusions was detected in all cases. The MIP genome profiles showed balanced profiles, with focal alterations of the YAP1 locus at 11q22.1–11q21.2 (7/14), MAMLD1 locus (Xp28) (10/14) and losses of chromosome arm 22q (5/14). Most patients were female (13/15) and younger than 3 years at diagnosis (12/15; median age, 8.2 months). Apart from one patient who died during surgery, all patients are alive without evidence of disease progression after receiving different treatment protocols, three without postoperative further treatment (median follow‐up, 4.84 years). In this to date, largest series of ependymomas with YAP1‐MAMLD1 fusions we show that they harbor characteristic histopathological, cytogenetic and imaging features, occur mostly in young girls under 3 years and are associated with good outcome. Therefore, this genetically defined neoplasm should be considered a distinct disease entity. The diagnosis should be confirmed by demonstration of the specific fusion. Further studies on large collaborative series are warranted to confirm our findings.

Cerebrospinal fluid flow increases from newborn to adult stages

Solute transport through the brain is of major importance for the clearance of toxic molecules and metabolites, and it plays key roles in the pathophysiology of the central nervous system. This solute transport notably depends on the cerebrospinal fluid (CSF) flow, which circulates in the subarachnoid spaces, the ventricles and the perivascular spaces. We hypothesized that the CSF flow may be different in the perinatal period compared to the adult period. Using in vivo magnetic resonance imaging (MRI) and near-infrared fluorescence imaging (NIRF), we assessed the dynamic of the CSF flow in rodents at different ages. By injecting a contrast agent into the CSF, we first used MRI to demonstrate that CSF flow gradually increases with age, with the adult pattern observed at P90. This observation was confirmed by NIRF, which revealed an increased CSF flow in P90 rats when compared with P4 rats not only at the surface of the brain but also deep in the brain structures. Lastly, we evaluated the exit routes of the CSF from the brain. We demonstrated that indocyanine green injected directly into the striatum spread throughout the parenchyma in adult rats, whereas it stayed at the injection point in P4 rats. Moreover, the ability of CSF to exit through the nasal mucosa was increased in the adult rodents. Our results provide evidence that the perinatal brain has nonoptimal CSF flow and exit and, thus, may have impaired clean-up capacity. © 2018 Wiley Periodicals, Inc. Develop Neurobiol, 2018.

Stromal striae: a new insight into corneal physiology and mechanics

We uncover the significance of a previously unappreciated structural feature in corneal stroma, important to its biomechanics. Vogt striae are a known clinical indicator of keratoconus, and consist of dark, vertical lines crossing the corneal depth. However we detected stromal striae in most corneas, not only keratoconus. We observed striae with multiple imaging modalities in 82% of 118 human corneas, with pathology-specific differences. Striae generally depart from anchor points at Descemet’s membrane in the posterior stroma obliquely in a V-shape, whereas in keratoconus, striae depart vertically from posterior toward anterior stroma. Optical coherence tomography shear wave elastography showed discontinuity of rigidity, and second harmonic generation and scanning electron microscopies showed undulation of lamellae at striae locations. Striae visibility decreased beyond physiological pressure and increased beyond physiological hydration. Immunohistology revealed striae to predominantly contain collagen VI, lumican and keratocan. The role of these regions of collagen VI linking sets of lamellae may be to absorb increases in intraocular pressure and external shocks.

Integrating Tenascin-C protein expression and 1q25 copy number status in pediatric intracranial ependymoma prognostication: A new model for risk stratification

PURPOSE

Despite multimodal therapy, prognosis of pediatric intracranial ependymomas remains poor with a 5-year survival rate below 70% and frequent late deaths.

EXPERIMENTAL DESIGN

This multicentric European study evaluated putative prognostic biomarkers. Tenascin-C (TNC) immunohistochemical expression and copy number status of 1q25 were retained for a pooled analysis of 5 independent cohorts. The prognostic value of TNC and 1q25 on the overall survival (OS) was assessed using a Cox model adjusted to age at diagnosis, tumor location, WHO grade, extent of resection, radiotherapy and stratified by cohort. Stratification on a predictor that did not satisfy the proportional hazards assumption was considered. Model performance was evaluated and an internal-external cross validation was performed.

RESULTS

Among complete cases with 5-year median follow-up (n = 470; 131 deaths), TNC and 1q25 gain were significantly associated with age at diagnosis and posterior fossa tumor location. 1q25 status added independent prognostic value for death beyond the classical variables with a hazard ratio (HR) = 2.19 95%CI = [1.29; 3.76] (p = 0.004), while TNC prognostic relation was tumor location-dependent with HR = 2.19 95%CI = [1.29; 3.76] (p = 0.004) in posterior fossa and HR = 0.64 [0.28; 1.48] (p = 0.295) in supratentorial (interaction p value = 0.015). The derived prognostic score identified 3 different robust risk groups. The omission of upfront RT was not associated with OS for good and intermediate prognostic groups while the absence of upfront RT was negatively associated with OS in the poor risk group.

CONCLUSION

Integrated TNC expression and 1q25 status are useful to better stratify patients and to eventually adapt treatment regimens in pediatric intracranial ependymoma.

Co-occurrence of histone H3 K27M and BRAF V600E mutations in paediatric midline grade I ganglioglioma

Ganglioglioma (GG) is a grade I tumor characterized by alterations in the MAPK pathway, including BRAF V600E mutation. Recently, diffuse midline glioma with an H3 K27M mutation was added to the WHO 2016 classification as a new grade IV entity. As co-occurrence of H3 K27M and BRAF V600E mutations has been reported in midline tumors and anaplastic GG, we searched for BRAF V600E and H3 K27M mutations in a series of 54 paediatric midline grade I GG (midline GG) to determine the frequency of double mutations and its relevance for prognosis. Twenty-seven patients (50%) possessed the BRAF V600E mutation. The frequency of the co-occurrence of H3F3A/BRAF mutations at diagnosis was 9.3%. No H3 K27M mutation was detected in the absence of the BRAF V600E mutation. Double-immunostaining revealed that BRAF V600E and H3 K27M mutant proteins were present in both the glial and neuronal components. Immunopositivity for the BRAF V600E mutant protein correlated with BRAF mutation status as detected by massARRAY or digital droplet PCR. The median follow-up of patients with double mutation was 4 years. One patient died of progressive disease 8 years after diagnosis, whereas the four other patients were all alive with stable disease at the last clinical follow-up (at 9 months, 1 year and 7 years) without adjuvant therapy. We demonstrate in this first series of midline GGs that the H3 K27M mutation can occur in association with the BRAF V600E mutation in grade I glioneuronal tumors. Despite the presence of H3 K27M mutations, these cases should not be graded and treated as grade IV tumors because they have a better spontaneous outcome than classic diffuse midline H3 K27M-mutant glioma. These data suggest that H3 K27M cannot be considered a specific hallmark of grade IV diffuse gliomas and highlight the importance of integrated histomolecular diagnosis in paediatric brain tumors.

Multimodal optical analysis discriminates freshly extracted human sample of gliomas, metastases and meningiomas from their appropriate controls

Delineating tumor margins as accurately as possible is of primordial importance in surgical oncology: extent of resection is associated with survival but respect of healthy surrounding tissue is necessary for preserved quality of life. The real-time analysis of the endogeneous fluorescence signal of brain tissues is a promising tool for defining margins of brain tumors. The present study aims to demonstrate the feasibility of multimodal optical analysis to discriminate fresh samples of gliomas, metastases and meningiomas from their appropriate controls. Tumor samples were studied on an optical fibered endoscope using spectral and fluorescence lifetime analysis and then on a multimodal set-up for acquiring spectral, one and two-photon fluorescence images, second harmonic generation signals and two-photon fluorescence lifetime datasets. The obtained data allowed us to differentiate healthy samples from tumor samples. These results confirmed the possible clinical relevance of this real-time multimodal optical analysis. This technique can be easily applied to neurosurgical procedures for a better delineation of surgical margins.

Multimodal optical analysis of meningioma and comparison with histopathology

Meningioma is the most frequent primary central nervous system tumor. The risk of recurrence and the prognosis are correlated with the extent of the resection that ideally encompasses the infiltrated dura mater and, if required, the infiltrated bone. No device can deliver real-time intraoperative histopathological information on the tumor environment to help the neurosurgeon to achieve a gross total removal. This study assessed the abilities of nonlinear microscopy to provide relevant and real-time data to help resection of meningiomas. Nine human meningioma samples (four World Health Organization Grade I, five Grade II) were analyzed using different optical modalities: spectral analysis and imaging, lifetime measurements, fluorescence lifetime imaging microscopy, fluorescence emitted under one- and two-photon excitation and the second-harmonic generation signal imaging using a multimodal setup. Nonlinear microscopy produced images close to histopathology as a gold standard. The second-harmonic generation signal delineated the collagen background and two-photon fluorescence underlined cell cytoplasm. The matching between fluorescence images and Hematoxylin and Eosin staining was possible in all cases. Grade I meningioma emitted less autofluorescence than Grade II meningioma and Grade II meningioma exhibited a distinct lifetime value. Autofluorescence was correlated with the proliferation rates and seemed to explain the observed differences between Grade I and II meningiomas. This preliminary multimodal study focused on human meningioma samples confirms the potential of tissue autofluorescence analysis and nonlinear microscopy in helping intraoperatively neurosurgeons to reach the actual boundaries of the tumor infiltration. Correspondence between H&E staining (top pictures) and the two-photon fluorescence imaging (bottom pictures).

Clinical, Imaging, Histopathological and Molecular Characterization of Anaplastic Ganglioglioma

Anaplastic ganglioglioma (AGG) is a rare and malignant variant of ganglioglioma. According to the World Health Organization classification version 2016, their histopathological grading criteria are still ill-defined. The aim of the present study was to assess the clinical, imaging, histopathological, and molecular characteristics and outcomes of AGGs in a large consecutive and retrospective adult and pediatric case series. Eighteen patients with AGGs (13 adults and 5 children) were identified (14 de novo and 4 secondary) from a cohort of 222 gangliogliomas (GG) (8%) treated at our institution between 2000 and 2015. AGGs represented a very aggressive disease with poor outcome (median progression-free survival, 10 months; median overall survival, 27 months). They were located in the temporal lobe only in 22% and presented with seizures (44%) or increased intracranial pressure (44%) at diagnosis. Concerning histopathological and molecular data, they shared morphological characteristics and BRAF V600E mutation (39%) with their benign counterparts but also showed hTERT promoter mutation (61%), p53 accumulation (39%), ATRX loss (17%), or p.K27M H3F3A mutation (17%). AGGs are malignant neoplasms requiring aggressive oncological treatment. In the perspective of targeted therapies, AGGs should be screened for BRAF V600E, hTERT, ATRX, and mutations of histone genes.