Disseminated diffuse midline glioma associated with poorly differentiated orbital lesion and metastases in an 8-year-old girl: case report and literature review.

BACKGROUND: Disseminated diffuse midline glioma (DMG) is a devastating diagnosis. Molecular subtyping has increased our understanding of this tumor. CASE: Here, we report the case of an 8-year-old girl who presented with symptoms of brainstem dysfunction and was found to have disseminated DMG with lesions in the pons, thalamus and bilateral temporal lobes. Molecular subtyping of the temporal lobe tumor tissue was consistent with H3 K27me3 loss and EZHIP overexpression, falling under the newly designated "H3 K27-altered" AQ5WHO subtype of DMG. Pathology from biopsy of the orbital lesion showed poorly differentiated rhabdoid-like disseminated tumor cells. The patient went on to develop lesions in the peritoneum, infratemporal fossa, and along the lumbosacral nerve roots. CONCLUSION: This unique case illustrates the aggressive behavior of H3 K27-altered tumors and their potential to metastasize.

Giant, symptomatic mixed vascular malformation containing a cavernoma, developmental venous anomaly, and capillary telangiectasia in a 19-month-old infant.

Intracranial mixed vascular malformations (MVMs) are defined as any combination of a developmental venous anomaly (DVA), cerebral cavernous malformation (CCM), capillary telangiectasia (CTG), or arteriovenous malformation (AVM) within a single, contiguous lesion. However, most MVMs described in the literature contain only 2 pathologically discrete malformations; juxtaposition of 3 or more abnormalities in a single lesion remains exceedingly rare. We present the case of a 19-month-old female with new onset focal seizures and a 4-cm right basal ganglia lesion initially believed to be an embryonal neoplasm. She subsequently underwent gross total resection (GTR) of the lesion via a transsylvian-transinsular approach. Intraoperatively, the lesion appeared to be heterogenous and highly vascular, with areas of purplish-gray friable tissue. Pathology confirmed the lesion to be a MVM containing a CCM, CTG, and a DVA. This appears to be the first reported case of such a lesion confirmed on pathology in the literature.

Comprehensive analysis of diverse low-grade neuroepithelial tumors with FGFR1 alterations reveals a distinct molecular signature of rosette-forming glioneuronal tumor.

The FGFR1 gene encoding fibroblast growth factor receptor 1 has emerged as a frequently altered oncogene in the pathogenesis of multiple low-grade neuroepithelial tumor (LGNET) subtypes including pilocytic astrocytoma, dysembryoplastic neuroepithelial tumor (DNT), rosette-forming glioneuronal tumor (RGNT), and extraventricular neurocytoma (EVN). These activating FGFR1 alterations in LGNET can include tandem duplication of the exons encoding the intracellular tyrosine kinase domain, in-frame gene fusions most often with TACC1 as the partner, or hotspot missense mutations within the tyrosine kinase domain (either at p.N546 or p.K656). However, the specificity of these different FGFR1 events for the various LGNET subtypes and accompanying genetic alterations are not well defined. Here we performed comprehensive genomic and epigenomic characterization on a diverse cohort of 30 LGNET with FGFR1 alterations. We identified that RGNT harbors a distinct epigenetic signature compared to other LGNET with FGFR1 alterations, and is uniquely characterized by FGFR1 kinase domain hotspot missense mutations in combination with either PIK3CA or PIK3R1 mutation, often with accompanying NF1 or PTPN11 mutation. In contrast, EVN harbors its own distinct epigenetic signature and is characterized by FGFR1-TACC1 fusion as the solitary pathogenic alteration. Additionally, DNT and pilocytic astrocytoma are characterized by either kinase domain tandem duplication or hotspot missense mutations, occasionally with accompanying NF1 or PTPN11 mutation, but lacking the accompanying PIK3CA or PIK3R1 mutation that characterizes RGNT. The glial component of LGNET with FGFR1 alterations typically has a predominantly oligodendroglial morphology, and many of the pilocytic astrocytomas with FGFR1 alterations lack the biphasic pattern, piloid processes, and Rosenthal fibers that characterize pilocytic astrocytomas with BRAF mutation or fusion. Together, this analysis improves the classification and histopathologic stratification of LGNET with FGFR1 alterations.

The genetic landscape of ganglioglioma.

Ganglioglioma is the most common epilepsy-associated neoplasm that accounts for approximately 2% of all primary brain tumors. While a subset of gangliogliomas are known to harbor the activating p.V600E mutation in the BRAF oncogene, the genetic alterations responsible for the remainder are largely unknown, as is the spectrum of any additional cooperating gene mutations or copy number alterations. We performed targeted next-generation sequencing that provides comprehensive assessment of mutations, gene fusions, and copy number alterations on a cohort of 40 gangliogliomas. Thirty-six harbored mutations predicted to activate the MAP kinase signaling pathway, including 18 with BRAF p.V600E mutation, 5 with variant BRAF mutation (including 4 cases with novel in-frame insertions at p.R506 in the ß3-αC loop of the kinase domain), 4 with BRAF fusion, 2 with KRAS mutation, 1 with RAF1 fusion, 1 with biallelic NF1 mutation, and 5 with FGFR1/2 alterations. Three gangliogliomas with BRAF p.V600E mutation had concurrent CDKN2A homozygous deletion and one additionally harbored a subclonal mutation in PTEN. Otherwise, no additional pathogenic mutations, fusions, amplifications, or deletions were identified in any of the other tumors. Amongst the 4 gangliogliomas without canonical MAP kinase pathway alterations identified, one epilepsy-associated tumor in the temporal lobe of a young child was found to harbor a novel ABL2-GAB2 gene fusion. The underlying genetic alterations did not show significant association with patient age or disease progression/recurrence in this cohort. Together, this study highlights that ganglioglioma is characterized by genetic alterations that activate the MAP kinase pathway, with only a small subset of cases that harbor additional pathogenic alterations such as CDKN2A deletion.

Infiltrative brainstem and cerebellar neurocytoma.

Neurocytomas are typically intraventricular in location, and extraventricular neurocytomas are uncommon. The authors report the unique case of a 15-year-old girl who was found to have a low-grade neurocytoma infiltrating the brainstem and cerebellum and spreading along the CSF pathways to the lateral and third ventricles. The patient underwent endoscopic third ventriculostomy to treat associated hydrocephalus, and biopsy specimens from intraventricular tumor nodules were obtained. Because of the low-grade pathology, the fact that the lesion was not amenable to resection, and the extensive radiation field required for radiation therapy, she has been treated conservatively with close follow-up. Over the course of almost 4 years since diagnosis, no additional treatment has been required. Neurocytoma with widespread infiltration of the brainstem and cerebellum has not been previously reported.

Apparent encephalocele in twin fetus papyraceus with twin-reversal arterial perfusion.

An apparently iniencephalic or exencephalic monoamniotic monochorionic female twin fetus, delivered as a fetus papyraceus at 28 weeks of gestation, had severe anomalies of the central nervous system and spine, including occipital encephalocele with a defect of the occipital bone. The encephalocele contained a spherical mass of autolyzed brain tissue without identifiable cerebellum or vermis. The cervical canal was widely patent dorsally, there were severe bony anomalies, including agenesis and fusion of vertebrae in the cervicothoracic spine. The upper limbs were absent. All organs were hypoplastic and autolyzed. The hypoplastic heart had three chambers. The placenta was monochorionic and monoamniotic; barium injection showed a twin-reversal arterial perfusion and entanglement of the umbilical cords.