Franck Bielle

Integrated multi-omics analysis of oligodendroglial tumours identifies three subgroups of 1p/19q co-deleted gliomas

Oligodendroglial tumours (OT) are a heterogeneous group of gliomas. Three molecular subgroups are currently distinguished on the basis of the IDH mutation and 1p/19q co-deletion. Here we present an integrated analysis of the transcriptome, genome and methylome of 156 OT. Not only does our multi-omics classification match the current classification but also reveals three subgroups within 1p/19q co-deleted tumours, associated with specific expression patterns of nervous system cell types: oligodendrocyte, oligodendrocyte precursor cell (OPC) and neuronal lineage. We confirm the validity of these three subgroups using public datasets. Importantly, the OPC-like group is associated with more aggressive clinical and molecular patterns, including MYC activation. We show that the MYC activation occurs through various alterations, including MYC genomic gain, MAX genomic loss, MYC hypomethylation and microRNA-34b/c down-regulation. In the lower grade glioma TCGA dataset, the OPC-like group is associated with a poorer outcome independently of histological grade. Our study reveals previously unrecognized heterogeneity among 1p/19q co-deleted tumours.

PHOX2B immunolabeling: a novel tool for the diagnosis of undifferentiated neuroblastomas among childhood small round blue-cell tumors.

Peripheral neuroblastic tumors are the most commonly occurring extracranial tumors in children. Although a reliable diagnosis is achievable in the majority of cases, diagnosis of a minority of peripheral neuroblastic tumor cases (especially undifferentiated neuroblastoma) poses a challenge compared with that of other pediatric small round blue-cell tumors. A panel of immunohistochemical markers and fusion transcripts is available for the diagnosis of such tumors, but the markers for neuroblastoma lack specificity and sensitivity. As the transcription factor PHOX2B is highly specific for the peripheral autonomic nervous system from which peripheral neuroblastic tumors are derived, we have assessed PHOX2B immunolabeling as a diagnostic tool in pediatric small round blue-cell tumors. We observed PHOX2B expression in all peripheral neuroblastic tumors, paragangliomas, and pheochromocytomas tested but in no other pediatric tumors among the 388 cases studied by expression microarray and the 109 cases studied by immunohistochemical analysis. We then assessed the results of PHOX2B immunohistochemistry in 12 cases of undifferentiated pediatric neoplasms: PHOX2B was expressed in 6/6 undifferentiated neuroblastomas and in no other small round blue-cell tumors. Finally, we showed that PHOX2B immunohistochemical analysis improves the diagnosis of undifferentiated neuroblastoma with high specificity and sensitivity.

Chordoid gliomas of the third ventricle share TTF-1 expression with organum vasculosum of the lamina terminalis.

Chordoid glioma of the third ventricle (CG3V) is a rare tumor developing in a stereotyped localization. It has been related to the circumventricular organ of the lamina terminalis, in the anterior part of the third ventricle, but its oncogenesis is poorly understood. TTF-1 transcription factor is involved in the development and adult physiology of the ventral forebrain. We studied the histopathologic and immunohistochemical features of a multicentric series of 17 cases of CG3V. We described additional histologic patterns (solid, fibrosing, and fusiform) to the typical chordoid pattern. TTF-1 was constantly expressed in CG3V, as in developing and adult lamina terminalis. The anti-TTF-1 SPT24 clone was more sensitive than the 8G7G3/1 clone. No mutation of IDH1 R132, IDH2 R172, or BRAF V600 codons was found. We showed TTF-1 as a useful marker for the diagnosis of CG3V and the understanding of its oncogenesis.

Unusual primary cerebral localization of a CIC-DUX4 translocation tumor of the Ewing sarcoma family

We report a late dural relapse of a resected and irradiated pineal parenchymal tumor of intermediate differentiation

K27M mutation in H3F3A in ganglioglioma grade I with spontaneous malignant transformation extends the histopathological spectrum of the histone H3 oncogenic pathway

Here we describe the presence of the mutation p.K27M of H3F3A (H3.3K27M) in two tumours of young patients with classical histopathology of ganglioglioma (grade I WHO 2007), although H3.3K27M represents a hallmark of midline High Grade Glioma (HGG). Ganglioglioma grade I is a rare, circumscribed, glioneuronal tumour of the central nervous system (CNS) that occurs most often in young patients, most frequently in the temporal lobe and presents with seizures [1]. The neuronal component consists of ganglion cells, abnormally grouped and occasionally binucleated. The glial component consists of piloid or fibrillary astrocytic elements, or of pseudo-oligodendroglial elements. Mitoses are occasional and necrosis is absent. Eosinophilic granular bodies (EGB) and perivascular lymphocytes are associated [1]. The glial component variably expresses GFAP and OLIG2 and the neuronal component variably expresses synaptophysin, chromogranin A and MAP2. The progenitor marker CD34 often shows an extravascular stellar immunostaining [1]. Ki67 labelling index is usually less than 3% and p53 immunostaining is negative. The majority of gangliogliomas are benign grade I tumours, however 6% present as grade III anaplastic ganglioglioma or undergo malignant transformation. Markers to predict anaplastic transformation of grade I tumours are poorly defined [1]. The most frequent genetic alterations in ganglioglioma are BRAF p.V600E mutation (40–60%), gain of chromosomes 7 (23%) and 5 (18%) [1–4]. Recurrent mutations in the genes H3F3A and HIST1H3B (encoding histones H3.3 and H3.1 respectively) were described in paediatric and adult HGG and carry a dismal prognosis [5–7]. These mutations show a distinct anatomical segregation: K27M mutation of H3F3A is observed in thalamus, pons and spinal cord, K27M mutation of HIST1H3B is specifically observed in diffuse intrinsic pontine gliomas and G34R/V mutation of H3F3A is observed in the cerebral hemispheres [5–7]. At position 27, lysine is replaced by methionine (K27M) resulting in decreased K27 trimethylation (H3K27me3) [5]. H3.3K27M immunolabelling shows 100% sensitivity and specificity compared to sequencing [5]. Recently, five H3.3K27M paediatric tumours with histopathology other than HGG were reported: three tumours of unclassified histopathology and harbouring BRAF V600E mutation [8], one ganglioglioma harbouring BRAF V600E mutation which underwent a delayed malignant transformation [9], a spinal pilocytic astrocytoma which underwent a delayed malignant transformation after 10 years [10]. Here we extend the histopathological spectrum of H3.3K27M tumours and present two extratemporal grade I gangliogliomas with secondary malignant transformation. One paediatric midline ganglioglioma had combined H3.3K27M and BRAF V600E mutations and its long-term malignant relapse was BRAF wild type. The second case represented a cerebellar tumour with a rapid malignant transformation. The first case was a 12-year-old girl diagnosed with a partially resected right thalamic tumour. Histopathology was of a ganglioglioma grade I. The tumour was reticulin free and composed of astrocytic piloid elements, pseudo-oligodendroglial elements and ganglionic cells associated with EGBs, lymphocytes and CD34 extravascular stellar immunostaining (Figure 1A–C). Binucleated chromogranin A positive cells and mononucleated synaptophysin expressing cells were detected (Figure 1D). The neurofilament immunolabelling confirmed the circumscribed nature of the tumour. The Ki67 labelling index was 2% (Figure 1E). The residual tumour was stable for 7 years until the patient presented with intracranial hypertension. MRI showed an in situ relapse (Figure 1G). The surgical resection was subtotal. Histopathology demonstrated an anaplastic ganglioglioma. The lesion contained lowgrade areas (Figure 1H) and anaplastic areas with high cellularity, marked atypia, mitotic activity exceeding 5 mitoses per 10 high power field (HPF), microvascular proliferation, pseudopalisading necrosis, high p53 expression and Ki67 index reaching 20% (Figure 1I).

Predictive factors of long-term outcomes of surgery for mesial temporal lobe epilepsy associated with hippocampal sclerosis

The reasons for failure of surgical treatment for mesial temporal lobe epilepsy (MTLE) associated with hippocampal sclerosis (HS) remain unclear. This retrospective study analyzed seizure, cognitive, and psychiatric outcomes, searching for factors associated with seizure relapse or cognitive and psychiatric deterioration after MTLE‐HS surgery.

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.

Tumor cells with neuronal intermediate progenitor features define a subgroup of 1p/19q co-deleted anaplastic gliomas

The integrated diagnosis of anaplastic oligodendroglioma, IDH mutant and 1p/19q co‐deleted, grade III (O3id) is a histomolecular entity that WHO 2016 classification distinguished from other diffuse gliomas by specific molecular alterations. In contrast, its cell portrait is less well known. The present study is focused on intertumor and intratumor, cell lineage‐oriented, heterogeneity in O3id. Based on pathological, transcriptomic and immunophenotypic studies, a novel subgroup of newly diagnosed O3id overexpressing neuronal intermediate progenitor (NIP) genes was identified. This NIP overexpression pattern in O3id is associated with: (i) morphological and immunohistochemical similarities with embryonic subventricular zone, (ii) proliferating tumor cell subpopulation with NIP features including expression of INSM1 and no expression of SOX9, (iii) mutations in critical genes involved in NIP biology and, (iv) increased tumor necrosis. Interestingly, NIP tumor cell subpopulation increases in O3id recurrence compared with paired newly diagnosed tumors. Our results, validated in an independent cohort, emphasize intertumor and intratumor heterogeneity in O3id and identified a tumor cell subpopulation exhibiting NIP characteristics that is potentially critical in oncogenesis of O3id. A better understanding of spatial and temporal intratumor cell heterogeneity in O3id will open new therapeutic avenues overcoming resistance to current antitumor treatments.

Highly specific determination of IDH status using edited in vivo magnetic resonance spectroscopy

Background Mutations in the isocitrate dehydrogenase (IDH) enzyme affect 40% of gliomas and represent a major diagnostic and prognostic marker. The goals of this study were to evaluate the performance of noninvasive magnetic resonance spectroscopy (MRS) methods to determine the IDH status of patients with brain gliomas through detection of the oncometabolite 2-hydroxyglutarate (2HG) and to compare performance of these methods with DNA sequencing and tissue 2HG analysis. Methods Twenty-four subjects with suspected diagnosis of low-grade glioma were included prospectively in the study. For all subjects, MRS data were acquired at 3T using 2 MRS methods, edited MRS using Mescher-Garwood point-resolved spectroscopy (MEGA-PRESS) sequence and a PRESS sequence optimized for 2HG detection, using a volume of interest larger than 6 mL. IDH mutational status was determined by a combination of automated immunohistochemical analysis and Sanger sequencing. Levels of 2HG in tissue samples measured by gas chromatography-mass spectrometry were compared with those estimated by MRS. Results Edited MRS provided 100% specificity and 100% sensitivity in the detection of 2HG. The 2HG levels estimated by this technique were in line with those derived from tissue samples. Optimized PRESS provided lower performance, in agreement with previous findings. Conclusions Our results suggest that edited MRS is one of the most reliable tools to predict IDH mutation noninvasively, showing high sensitivity and specificity for 2HG detection. Integrating edited MRS in clinical practice may be highly beneficial for noninvasive diagnosis of glioma, prognostic assessment, and treatment planning.

Transdifferentiation of Neuroendocrine Cells: Gangliocytoma Associated With Two Pituitary Adenomas of Different Lineage in Men1

Gangliocytomas are rare and benign neuronal cell tumors, mostly found in the hypothalamic and sellar regions. Their histogenesis is still the subject of discussions. Herein we present a unique case of a pituitary gangliocytoma associated with a prolactinoma and a corticotroph adenoma in a patient affected by MEN1. The histologic study revealed shared features between adenomatous and neuronal cells, supporting the etiological hypothesis of a common origin or a phenomenon of transdifferentiation. Furthermore, gangliocytoma could be a new tumor related to MEN1. The clinical and histologic observations are discussed and the literature on the topic is reviewed.