An integrative histopathological and epigenetic characterization of primary intracranial mesenchymal tumors, FET:CREB-fused broadening the spectrum of tumor entities in comparison with their soft tissue counterparts.

FET:CREB fusions have been described in a variety of tumors from various phenotypes. Recently, these fusion transcripts were reported in intracranial tumors, variably named intracranial mesenchymal myxoid tumors or angiomatoid fibrous histiocytomas. Controversy remains concerning the terminology for these tumors. Here, we report 11 cases of central nervous system mesenchymal tumors with proven FET:CREB fusion. Most DNA methylation profiles were not classifiable using the Heidelberg Brain Tumor or Sarcoma Classifier (v11b4/v12.2). However, by using unsupervised t-SNE and hierarchical clustering analyses, six of the cases constituted a distinct cluster. The remaining four tumors showed no obvious relation to any of the other referenced classes but were close to the clusters of extra-CNS angiomatoid fibrous histiocytomas (n = 1), clear cell sarcomas (n = 1), or solitary fibrous tumors (n = 2). Our findings confirm that intracranial FET:CREB-fused tumors do not represent a single molecular tumor entity, although most samples clustered close to each other, indicating the existence of a distinct epigenetic group that could potentially be partially masked by the low number of cases included. Further analyses are needed to characterize intracranial FET:CREB fused-defined tumors in more detail.

[Analysis of interference criteria for the validation of a method file: HPS staining after fixation with zinc-formalin in comparison to fixation with the classical 4% buffered formalin solution]. / Étude de l'item d'interférence dans un dossier de validation de méthode : cas de la coloration HPS après fixation en formol-zinc et comparaison à la fixation en formol tamponné à 4.

INTRODUCTION: The department of neuropathology of Sainte-Anne Hospital uses zinc-formalin as the fixative agent for its samples. No publication referenced in Pubmed has proven the validity of this fixative agent. In the context of the accreditation of our standard staining (HPS for Hemalun-Phloxin-Saffron), we started a file for the validation of this method in which the fixative agent constitutes an « interfering ¼ substance which can modify the quality of the technique. The aim of this study was to prove that the use of zinc-formalin as a fixative agent is as suitable as the fixation with 4 % buffered formalin. MATERIALS AND METHODS: A cohort of samples fixed by zinc-formalin and by 4 % buffered formalin was performed on fresh samples, then cut and stained by HPS. The slides were interpreted by three pathologists (one of them was outside our centre)  ``blind '' to the fixative agent and they evaluated four criteria (general quality of the staining, components of the extracellular matrix, cytoplasmic details, and nuclear details) and scored them (from 0 to 3) according to the Association française en assurance qualité (AFAQAP) recommendations. RESULTS: The cohort included 43 samples. The results of the analysis showed that for samples fixed by zinc-formalin, three of the four criteria obtained significantly a better score than the samples fixed by classical formalin. DISCUSSION AND CONCLUSIONS: Our results show that the zinc-formalin fixative does not constitute an  ``interfering '' agent for the quality of the HPS staining for neuropathological samples.

[A case of bronchial mucous gland adenoma: A rare diagnosis that should not be mistaken!] / Un cas d'adénome muqueux glandulaire bronchique : un diagnostic rare à ne pas méconnaître !

We report the case of a 32-year-old man, who was admitted for a recurrent pneumopathy. The thoracic computed tomography revealed a small well-circumscribed lesion of the lower right lobe of the lung. Microscopic examination from the biopsy material of the endoscopy concluded a mucoepidermoid carcinoma. A lobectomy was realized. Microscopic examination revealed the presence of a well-delineated lesion composed of glands and cysts containing mucous and limited by mucous and cylindric and ciliated cells without atypia. The proliferation index was very low. A diagnosis of mucous gland adenoma was made. It is an exceptional tumor and is very difficult to diagnose on biopsy material but should be known by pathologists. It is associated with a good prognosis. The aims of our observation are to present the macroscopic and microscopic features of this tumor and data from recent literature review to better diagnose it. This is also the second observation with molecular details for this entity.

Prognostic relevance of adding MRI data to WHO 2016 and cIMPACT-NOW updates for diffuse astrocytic tumors in adults. Working toward the extended use of MRI data in integrated glioma diagnosis.

Assess the contribution of preoperative MRI data in improving grading of adult astrocytomas reclassified according to the WHO 2016 and cIMPACT-NOW update 3. Retrospective unicentric cohort study of 679 adult patients treated for newly diagnosed diffuse astrocytic and oligodendroglial tumors (January 2006-December 2016). We first systematically compared radiological (contrast enhancement present [CE+] vs. absent [CE-]) and histopathological findings (microvascular proliferation present [MPV+] vs. absent [MPV-]) to validate whether this comparing step of neoangiogenesis represents an efficient method to appreciate the representativity of the tumoral sampling. We focused on 629 cases of astrocytomas for radio-histological integrated analyses. In 598 cases (95.1%), neoangiogenesis evaluated by MRI or histology (CE+/MPV+ or CE-/MPV-) was identical. For the CE+/MPV- and CE-/MPV+ groups (23 cases), the radio-histological face-to-face evaluation allowed us to assess that for 13 cases (56.5%) the reason for this discrepancy was an undersampled tumor. We analyzed the group of CE+/MPV- (n = 8) and CE-/MPV+ (n = 2) in verified image-guided tumoral samples. Finally, we identified three new prognostic subgroups for molecular glioblastomas: (1) "non-representative sampling" (n = 9), (2) "Non neoangiogenic glioblastoma at the time of diagnosis, without contrast enhancement and microvascular proliferation" (n = 8), and (3) "contrast enhancing glioblastoma but without microvascular proliferation in a representative sample" (n = 4). Neoangiogenesis processes should be assessed to improve the prognosis accuracy of the current integrated diagnosis. We suggest adding imaging analyses during the neuropathological analysis of astrocytomas in adults.

Diagnostic Accuracy of a Reduced Immunohistochemical Panel in Medulloblastoma Molecular Subtyping, Correlated to DNA-methylation Analysis.

Medulloblastomas (MBs) are the most frequent childhood malignant brain tumor. Four histopathologic variants and 4 genetic subgroups have been defined in the World Health Organization (WHO) 2016 Classification and constitute major risk stratification items directly affecting the patient management. Although MB subgroups have been molecularly defined, immunohistochemical surrogates are needed. The aim of our retrospective study was to evaluate the concordance between immunohistochemistry, using 4 antibodies (YAP1, GAB1, OTX2, and ß-catenin), and DNA-methylation profiling in MB subgrouping. From a series of 155 MBs, the κ coefficient of concordance was almost perfect (0.90), with only 8/152 discrepant cases (no DNA-methylation analysis was available in 3 cases). Interestingly, the discrepancies mostly concerned (7/8 cases) MBs with divergent differentiations (myogenic, melanotic, and others) with all of those classified into group 3 (n=6) and group 4 (n=1) by DNA-methylation profiling. Another discrepant case concerned a WNT-activated MB (showing only 1% of immunopositive tumor cell nuclei), highlighting the difficulties of determining an appropriate ß-catenin immunostaining cutoff. The high concordance of the routine immunohistochemical panel (YAP1, GAB1, OTX2, and ß-catenin) and DNA-methylation profiling confirm its utility as a reliable predictive marker of molecular subtype in MBs. We analyzed the accuracy of 10 different IHC combinations for the determination of MB subtype and found that a combination of 2 antibodies (YAP1 and OTX2) allows for the successful characterization of 144 cases of 152 cases. Finally, our series extends the molecular data of the rare morphologic variant of MBs with melanotic/myogenic differentiations.

Embryonal tumor with multilayered rosettes, C19MC-altered with sarcomatous differentiation: histopathologic and molecular characterization of one case.

Embryonal tumor with multilayered rosettes, constitutes an aggressive and rare pediatric embryonal tumor of the central nervous system characterized by alterations of the C19MC locus at 19q13.12. Embryonal tumors with multilayered rosettes (ETMRs) span a broad histopathological spectrum with primitive neural features and abundant neuropil. Before the molecular definition of this entity, exceptional cases with heterologous differentiation have been evidenced in the literature. Herein, we report the first case of an ETMR featuring a sarcomatous component with proven C19MC alteration in both components by an in situ hybridization analysis. This data supports the hypothesis of a divergent differentiation of tumoral cells in this case.

High-grade gliomas in adolescents and young adults highlight histomolecular differences from their adult and pediatric counterparts.

BACKGROUND: Considering that pediatric high-grade gliomas (HGGs) are biologically distinct from their adult counterparts, the objective of this study was to define the landscape of HGGs in adolescents and young adults (AYAs). METHODS: We performed a multicentric retrospective study of 112 AYAs from adult and pediatric Ile-de-France neurosurgical units, treated between 1998 and 2013 to analyze their clinicoradiological and histomolecular profiles. The inclusion criteria were age between 15 and 25 years, histopathological HGG diagnosis, available clinical data, and preoperative and follow-up MRI. MRI and tumoral samples were centrally reviewed. Immunohistochemistry and complementary molecular techniques such as targeted/next-generation sequencing, whole exome sequencing, and DNA-methylation analyses were performed to achieve an integrated diagnosis according to the 2016 World Health Organization (WHO) classification. RESULTS: Based on 80 documented AYA patients, HGGs constitute heterogeneous clinicopathological and molecular groups, with a predominant representation of pediatric subtypes (histone H3-mutants, 40%) but also adult subtypes (isocitrate dehydrogenase [IDH] mutants, 28%) characterized by the rarity of oligodendrogliomas, IDH mutants, and 1p/19q codeletion and the relative high frequency of "rare adult IDH mutations" (20%). H3G34-mutants (14%) represent the most specific subgroup in AYAs. In the H3K27-mutant subgroup, non-brainstem diffuse midline gliomas are more frequent (66.7%) than diffuse intrinsic pontine gliomas (23.8%), contrary to what is observed in children. We found that WHO grade has no prognostic value, but molecular subgrouping has major prognostic importance. CONCLUSIONS: HGGs in AYAs could benefit from a specific classification, driven by molecular subtyping rather than age group. Collaborative efforts are needed from pediatric and adult neuro-oncology teams to improve the management of HGGs in AYAs.

Intracranial chondromas: A histopathologic and molecular study of three cases.

AIMS: Meningeal chondromas constitute a small fraction of central nervous system tumors, with only 61 cases reported in the literature. Somatic mutations of IDH1/2 genes have been described in enchondromas, and, in soft-tissue chondromas, rearrangements of the HMGA2 gene have been reported. The aim of our study was to perform molecular analyses of 3 additional cases and to do a complete review of the literature to better characterize this rare entity. MATERIALS AND METHODS: Here, we report 3 cases of primitive meningeal chondromas in children and young adults. Immunohistochemical analyses for HMGA2 and IDH1R132H, molecular analyses of IDH1/2 mutations, and FISH analysis of the HMGA2 locus were performed. RESULTS: Immunohistochemical analyses of all cases were negative for IDH1R132H and HMGA2 proteins. Molecular analyses failed to reveal IDH1/2 mutations, and FISH analyses did not evidence any HMGA2 rearrangements. Similarly to what is reported in the literature, the 3 meningeal chondromas in this study were benign tumors with no recurrence after complete resection with a follow-up of 85, 46, and 89 months. CONCLUSION: Meningeal chondroma is rare. It affects predominantly young adults and has a good outcome. No molecular alterations have currently been described in this entity.

The histomolecular criteria established for adult anaplastic pilocytic astrocytoma are not applicable to the pediatric population.

Pilocytic astrocytoma (PA) is the most common pediatric glioma, arising from a single driver MAPK pathway alteration. Classified as a grade I tumor according to the 2016 WHO classification, prognosis is excellent with a 10-year survival rate > 95% after surgery. However, rare cases present with anaplastic features, including an unexpected high mitotic/proliferative index, thus posing a diagnostic and therapeutic challenge. Based on small histomolecular series and case reports, such tumors arising at the time of diagnosis or recurrence have been designated by many names including pilocytic astrocytoma with anaplastic features (PAAF). Recent DNA methylation-profiling studies performed mainly on adult cases have revealed that PAAF exhibit a specific methylation signature, thus constituting a distinct methylation class from typical PA [methylation class anaplastic astrocytoma with piloid features-(MC-AAP)]. However, the diagnostic and prognostic significance of MC-AAP remains to be determined in children. We performed an integrative work on the largest pediatric cohort of PAAF, defined according to strict criteria: morphology compatible with the diagnosis of PA, with or without necrosis, ≥ 4 mitoses for 2.3 mm2, and MAPK pathway alteration. We subjected 31 tumors to clinical, imaging, morphological and molecular analyses, including DNA methylation profiling. We identified only one tumor belonging to the MC-AAP (3%), the others exhibiting a methylation profile typical for PA (77%), IDH-wild-type glioblastoma (7%), and diffuse leptomeningeal glioneuronal tumor (3%), while three cases (10%) did not match to a known DNA methylation class. No significant outcome differences were observed between PAAF with necrosis versus no necrosis (p = 0.07), or with 4-6 mitoses versus 7 or more mitoses (p = 0.857). Our findings argue that the diagnostic histomolecular criteria established for anaplasia in adult PA are not of diagnostic or prognostic value in a pediatric setting. Further extensive and comprehensive integrative studies are necessary to accurately define this exceptional entity in children.

H3F3A-G34R mutant high grade neuroepithelial neoplasms with glial and dysplastic ganglion cell components.

The recently described malignant neuro-epithelial tumors with histone H3F3A point mutations at G34 (NET-H3-G34) occur most often in cerebral hemispheres of teenagers and young adults, and have a generally adverse prognosis. These tumors have been histologically classified as glioblastoma or primitive neuroectodermal tumor (PNET) in the past, and have not been defined as a separate entity in the revised WHO classification of tumors of the CNS 2016. Here, we report two cases of NET-H3-G34 with glial and dysplastic ganglion cell components affecting teenagers. Patients were treated with surgery and radiochemotherapy with temozolomide. One patient underwent partial resection and deceased 21 months after diagnosis, while the other patient is alive without evidence of disease 15 months after total resection. So far, a dysplastic ganglion cell component has not been described in NET-H-G34, and its presence raises a possible relation to (anaplastic) gangliogliomas. Genome-wide copy number analysis did not provide unequivocal evidence that these tumors represent anaplastic variants of gangliogliomas, as opposed to NET-H3-G34. Our observations expand the morphologic spectrum of NET-H3-G34. Further cases of NET-H3-G34 with dysplastic ganglion cells should be clinically followed to find differences or similarities in their biological behavior, as compared to NET-H3-G34 and anaplastic gangliogliomas.

Neurological Involvement in Childhood Evans Syndrome.

PURPOSE: Immune thrombocytopenic purpura (ITP) and autoimmune hemolytic anemia (AIHA) are associated in the definition of Evans syndrome (ES). The occurrence of neurological involvement in this population is poorly described and suggests an underlying primary immunodeficiency (PID). We aimed to describe the clinical manifestations, evolution, and PID profiles of these patients. METHODS: OBS'CEREVANCE is a French, nationwide prospective cohort that includes children with chronic ITP, AIHA, and ES. Patients with a neurological involvement were described. Centralized radiological and pathological reviews and genetic analyses were performed. RESULTS: On October 2016, eight patients (7/181 ES, 1/371 AIHA, and 0/615 ITP) were identified, all male, with a median age (range) at cytopenia onset of 11.5 years (1.6-15.8). Neurological symptoms appeared with a median delay of 6 years (2.5-18) after cytopenia and were polymorphic: seizures (n = 4), cranial nerve palsy (n = 2), Brown-Sequard syndrome (n = 2), intracranial pressure (n = 2), vertigo (n = 1), and/or sensory neuropathy (n = 1). Magnetic resonance imaging (MRI) showed inflammatory lesions, confirmed by pathology for five patients with macrophagic or lymphoplasmocytic infiltrates. All patients had other relevant immunopathological manifestations: pulmonary nodules (n = 6), lymphoproliferation (n = 4), abnormal immunophenotype (n = 8), and hypogammaglobulinemia (n = 7). Treatment consisted of steroids that improved symptomatology and MRI. Five patients relapsed and three had an asymptomatic radiological progression. A PID was identified in 3/8 patients: 22q11.2 microdeletion (n = 1) and CTLA deficiency (n = 2). CONCLUSION: Neurological involvement is a rare and severe late event in the course of childhood ES, which can reveal an underlying PID. Imaging and pathology examination highlight a causative immune dysregulation that may guide targeted therapeutic strategies.

ESWR1-CREM Fusion in an Intracranial Myxoid Angiomatoid Fibrous Histiocytoma-Like Tumor: A Case Report and Literature Review.

Gene fusions of EWSR1 with members of the CREB family of transcription factors (CREB1, ATF1, and CREM) have recently been described in exceptional intracranial myxoid mesenchymal tumors. Although this is a known gene fusion found in various mesenchymal tumors, EWSR1 fusion with CREM has only been observed in 3 intracranial myxoid tumors. In this paper, we present 1 such tumor with in-depth histopathological description and long-term follow-up. There is controversy regarding whether these tumors represent a novel entity or simply an intracranial localization of the myxoid variant of angiomatoid fibrous histiocytoma, a rare soft tissue tumor of the extremities. Out of 11 cases mentioned in the literature, the 3 isolated case reports by Dunham et al, Ochalski et al, and Alshareef et al are designated as angiomatoid fibrous histiocytoma, whereas the others are defined as a novel tumoral entity called intracranial myxoid mesenchymal tumor with EWSR1-CREB fusion. We believe the vast morphological and immunohistochemical spectrum of angiomatoid fibrous histiocytoma makes it difficult to dismiss this diagnosis.