Abstract Background PALB2 is a core component of the homologous recombination (HR) DNA repair machinery through its interaction with BRCA2. Germline pathogenic variants in PALB2 confer cancer susceptibility and are implicated in Fanconi anaemia; however, their role in CNS tumorigenesis remains uncertain. We describe the clinicopathological and molecular features of an exceptionally rare pediatric high-grade glioma associated with a germline PALB2 variant—only the second case reported to date. Case report A 5-year-old boy presented with new-onset seizures. Brain MRI demonstrated partly contiguous, infiltrative, non-enhancing lesions involving the left insula/basal ganglia and the right middle cerebellar peduncle and white matter, without spinal dissemination. Supratentorial biopsy revealed a cellular astrocytic glioma composed of pleomorphic cells within a fibrillary–microcystic matrix, interspersed with frequent bizarre multinucleated forms showing nuclear pseudoinclusions. Mitotic figures were uncommon, and necrosis was absent. Immunohistochemistry demonstrated diffuse GFAP, Olig2, and nestin positivity, with strong p53 overexpression. DNA methylation profiling (Heidelberg Epignostix, Brain tumor classifier v12.8) did not assign a diagnostic class. Copy number analysis demonstrated multiple high-risk alterations, including EGFR amplification, gains of MET and MYC, and homozygous NF1 loss. Targeted DNA/RNA panel and whole-genome sequencing identified a pathogenic heterozygous PALB2 variant confirmed as germline, alongside a somatic TP53 mutation. Whole-genome ploidy gain (2.8) and chromoanagenesis events were present. Tumor mutational burden was 1.85 mut/Mb, with mutational signatures consistent with HR deficiency. Fanconi anaemia was excluded by chromosomal breakage studies. CSF sample was clear. The patient commenced radiotherapy (54 Gy in 30 fractions) with concomitant temozolomide. Conclusion This case highlights a novel HR-deficient pHGG with a germline PALB2 variant, exhibiting a gliomatosis cerebri–like growth pattern, consistent with a prior report[1]. The tumor’s location precludes complete resection and this case underscores the challenges of managing such HR-deficient pediatric gliomas and the potential role for targeted therapies. 1. Zhong Y, Schubert J, Wu J, Xu F, Lin F, Cao K, Zelley K, Luo M, Foster JB, Cole KA, MacFarland SP. A germline PALB2 pathogenic variant identified in a pediatric high-grade glioma. Molecular Case Studies. 2020 Aug 1;6(4):a005397.

Prostate-specific membrane antigen (PSMA) is upregulated in high-grade glioma (HGG). This study aimed, firstly, to establish dosimetry for the radionuclide [68Ga]-PSMA-11 in HGG patients; secondly, to determine theoretical tumour doses for [177Lu]-PSMA, a potential therapeutic radionuclide; thirdly, to assess PSMA immunohistochemistry in targeted intra-operative HGG biopsies. Three HGG patients underwent PET-MRI after injection of 185 MBq [68Ga]-PSMA-11. Targeted intra-operative HGG biopsies were immunostained for PSMA and endothelium (CD34). There was durable, heterogeneous uptake of [ 68Ga]-PSMA-11 with moderate SUVmax (4.2-5.0) and high TBR (60-183). [68Ga]-PSMA-11 delivered a tumour dose of 0.01-0.03 mGy/MBq corresponding to 0.38-1.10 mGy/MBq for [177Lu]-PSMA. PSMA staining was predominantly seen in necrotic/proliferating CD34-positive cells. HGGs exhibited moderate and heterogeneous [68Ga]-PSMA-11 uptake, corresponding to a theoretical [177Lu] tumour dose lower than conventional external beam radiotherapy but within the range used for theranostic treatment in prostate cancer. PSMA staining was most prevalent in regions of tumour with necrotic/proliferating endothelium.

Purpose High-grade gliomas (HGG) are the most common intracranial tumors in children with replication repair deficiency (RRD) syndromes. Defective DNA repair leads to a high mutational burden, providing biological rationale for immune checkpoint inhibitors (ICI). However, responses to ICI are heterogeneous, and resistance mechanisms remain poorly understood. We report on the experience of the Paediatric & TYA Neuro-Oncology South London Network (SLN) and collaborators on the safety and efficacy of ICI in RRD-HGG. Methods Clinical, histopathological, molecular, and survival data were collected from children with molecularly confirmed RRD-HGG treated with ICI at SLN between 2019–2023. Descriptive statistics were used for demographics. Survival outcomes were analyzed using Kaplan-Meier estimates and univariable Cox proportional hazards models. Results Six patients were identified (Lynch syndrome n = 4,constitutional mismatch repair deficiency n = 2). Median age 9.6 years (range 2.74–11.02). ICI was administered upfront, at relapse, or at both stages (n = 2 each). No grade 4–5 toxicities were observed. Two patients treated upfront achieved sustained responses of 14 and 26.5 months, with one remaining in complete remission at last follow-up. Median progression-free survival from first ICI exposure was 4.1 months (95% CI 0.13–8.06; range 0.6–26.5), and median overall survival was 11.1 months (95% CI 10.06–12.14; range 10.2–35.3). Conclusions ICI use in RRD-HGG is biologically justified, but optimal agents, combinations, and predictive biomarkers need yet to be fully determined. Given the rarity of RRD-HGG, international collaborations, such as the International Replication Repair Deficiency Consortium (IRRDC), are essential to advance treatment strategies for these patients.

Background:Granular cell astrocytoma (GCA) is a rare, morphologically distinct variant of IDH-wildtype glioblastoma that can appear deceptively low-grade yet behave aggressively. Its molecular features remain poorly defined, and no methylation-based classification has previously been reported. Methods:Two GCAs diagnosed in our clinical neuropathology department were described with the integration of clinical, intraoperative, histopathological, and molecular data, including DNA methylation profiling, a targeted next-generation sequencing panel, and, in one case, whole genome sequencing (WGS). Results:The patients were aged 63 and 54 years old, respectively, both presenting with supratentorial tumors showing granular cell morphology. Case 1 showed a densely cellular tumor composed entirely of bland-appearing granular cells without a conventional astrocytic component. Case 2 showed low-grade granular cell areas transitioning into high-grade astrocytic regions with mitoses, microvascular proliferation, and necrosis. Despite these morphological differences, both cases matched the methylation class "Glioblastoma, IDH-wildtype, mesenchymal subtype" and shared molecular features typical of glioblastoma, including chromosome +7/-10 and CDKN2A/B deletion. Both patients harbored oncogenic NF1 variants. WGS in Case 2 also revealed homozygous MTAP loss and chromoanasynthesis on chromosome 9. Case 1 received Stupp protocol chemoradiotherapy, recurred after 3 months of treatment, and died 11 months after diagnosis. Case 2 has progressed with a new posterior fossa lesion while on adjuvant temozolomide. Conclusion:These cases demonstrate that GCAs span a morphological spectrum yet molecularly correspond to the mesenchymal subtype of IDH-wildtype glioblastoma. Integrated molecular testing is therefore essential for accurate diagnosis and for guiding clinical management, including consideration for potential clinical trial enrollment.

Atypical frontotemporal lobar degeneration with ubiquitin-positive inclusions (aFTLD-U) is neuropathologically characterized by aggregation of the FET family of proteins and clinically manifests as sporadic young-onset frontotemporal dementia. Here we describe a major risk locus on chr15q14 identified through a genome-wide association study in 59 pathologically confirmed aFTLD-U cases and 3,153 controls (lead single nucleotide polymorphism rs549846383, P = 5.85 × 10-21, odds ratio 26.7). When combined with data from 28 additional aFTLD-U cases, 3,712 controls and 3,215 individuals with other neurodegenerative diseases and by leveraging in-house and public long-read genome sequencing data from 1,715 individuals, we identified a tandem repeat expansion on the associated haplotypes in an intron of GOLGA8A. We found variation in repeat length, motif length, and motif sequence, with long CT-dimer expansions strongly associated with aFTLD-U. Although the functional consequence of this repeat remains unknown, its presence in nearly 60% of aFTLD-U cases points to a fundamental role in disease pathogenesis.

Intracranial dermoid cysts are benign lesions that may be diagnosed incidentally or present symptomatically due to mass effect-focal neurological deficits, seizures and/or hydrocephalus-or chemical meningitis secondary to spontaneous rupture. The use of tubular retractors in minimally invasive parafascicular surgery (tsMIPS) has been described extensively as a technique to preserve neurological function whilst safely maximizing the extent of resection. The authors present the first use of the tsMIPS approach for removal of a dermoid cyst in a 68-year-old female who presented with abulia and seizures due to a large Sylvian fissure dermoid cyst. This approach minimized trauma to surrounding cortical-subcortical structures, as supported by connectome analyses, without sacrificing visualization of the operative field. Additionally, itavoided manipulation of the lenticulostriate arteries attached to the walls of the dermoid cyst. The use of an endoscope ensured complete drainage of the cyst components and therefore the effectiveness of the procedure.

The age-associated neurodegenerative disorder, Lewy body dementia (LBD), encompasses neuropsychiatric symptom-overlapping Dementia with Lewy bodies (DLB) and Parkinson's Disease with Dementia (PDD). We characterised how differential mitochondrial DNA (mtDNA) profiles contribute to neurotype-specific neurodegeneration and thereby clinicopathological heterogeneity, between LBD's syndromes. We further characterised key nuclear-encoding genes' recalibrations in response to such mtDNA changes. In post-mortem 'single-cell' acetylcholine- and noradrenaline-producing neurons, respectively of the pedunculopontine nucleus (PPN) and locus coeruleus (LC) from DLB, PDD and neurological-control brains, we quantified 'major arc'-locating mtDNA deletions (mtDels) and -copy number (mtCN), and measured mRNA levels of nuclear-encoding genes regulating mtDNA maintenance, -biogenesis and mitophagy. DLB cases' OXPHOS defect instigating mtDel burden was higher in both neurotypes than PDD. In DLB, mtCN was reduced for both neurotypes, but PDD cases revealed mtDNA depletion in LC-noradrenergic neurons only. DLB patients' shorter survival correlated with PPN-cholinergic neurons' mtDel levels, inversely with wild-type mtCN, implying that such neurons' inability to maintain sufficient wild-type mtDNA content drive DLBs' rapid psycho-cognitive manifestations. Contrastingly, PDD's longer disease duration allowed compensation against mtDels' clonal expansion in PPN-cholinergic neurons. Moreover, PDD induced mRNA depletion of a mitochondrial genome maintenance gene in PPN-cholinergic neurons, whilst LC-noradrenergic neurons displayed reduced expression of a mitophagy regulating gene. Here we identify mitochondrial genome maintenance and mitophagy pathway enrichment as therapeutic targets to offset defective mtDNA within pontine cholinergic and noradrenergic neurons of PDD patients. The pronounced LBD subtype-related mitochondria-nuclear genetic differences question the consensus that pathology converges at disease end-stage, calling for LBD subtype and neurotype-specific therapeutics.

AIMS:Evidence suggests Alzheimer's disease (AD) patients are at increased risk of epilepsy and that seizure incidence is associated with faster cognitive decline. Previous studies indicate hyperphosphorylated tau may play a role in this disease association; however, abnormal TDP-43 and α-synuclein deposition have not been extensively examined. METHODS:Clinical and neuropathological records of AD cases over a 5-year period were retrieved from the London Neurodegenerative Diseases Brain Bank. The 114 cases were categorised into three groups: AD plus epilepsy, AD plus hippocampal sclerosis (HS) and AD only. Semi-quantitative scores for tau, TDP-43 and α-synuclein pathology within the middle temporal gyrus, hippocampus and amygdala were compared between groups. RESULTS:A 12% incidence of epilepsy and/or epileptic symptomology was found among the cohort. Twelve cases (11%) showed HS. No significant difference in tau pathology scores was seen between groups. However, a significantly higher score for TDP-43 was seen in AD plus epilepsy compared with AD only in the middle temporal gyrus (p = 0.004). The burden of α-synuclein pathology was increased in the amygdala of AD plus epilepsy and AD plus HS. CONCLUSIONS:The incidence of epilepsy within this AD cohort is higher than expected within the general population (even when matched for age), and this may be associated with increased TDP-43 burden. Understanding the relationship between AD and epilepsy may highlight mechanisms of cellular damage and tissue vulnerability.

Mechanistic target of rapamycin (mTOR) is a highly conserved serine/threonine kinase that regulates key cellular processes including cell growth, autophagy and metabolism. Hyperactivation of the mTOR pathway causes a group of rare and ultrarare genetic diseases. mTOR pathway diseases have diverse clinical manifestations that are managed by distinct medical disciplines but share a common underlying molecular basis. There is a now a deep understanding of the molecular underpinning that regulates the mTOR pathway but effective treatments for most mTOR pathway diseases are lacking. Translating scientific knowledge into clinical applications to benefit the unmet clinical needs of patients is a major challenge common to many rare diseases. In this article we expound how mTOR pathway diseases provide an opportunity to coordinate basic and translational disease research across the group, together with industry, medical research foundations, charities and patient groups, by pooling expertise and driving progress to benefit patients. We outline the germline and somatic mutations in the mTOR pathway that cause rare diseases and summarise the prevalence, genetic basis, clinical manifestations, pathophysiology and current treatments for each disease in this group. We describe the challenges and opportunities for progress in elucidating the underlying mechanisms, improving diagnosis and prognosis, as well as the development and approval of new therapies for mTOR pathway diseases. We illustrate the crucial role of patient public involvement and engagement in rare disease and mTOR pathway disease research. Finally, we explain how the mTOR Pathway Diseases node, part of the Research Disease Research UK Platform, will address these challenges to improve the understanding, diagnosis and treatment of mTOR pathway diseases.

Histone mutations (H3 K27M, H3 G34R/V) are molecular features defining subtypes of paediatric-type diffuse high-grade gliomas (HGG) (diffuse midline glioma (DMG), H3 K27-altered, diffuse hemispheric glioma (DHG), H3 G34-mutant). The WHO classification recognises in exceptional cases, these mutations co-occur. We report one such case of a 2-year-old female presenting with neurological symptoms; MRI imaging identified a brainstem lesion which was biopsied. Histology showed diffusely infiltrating pleomorphic astrocytes, multinucleated cells, and conspicuous mitotic activity; the diagnosis was DMG, H3 K27-altered (immunohistochemistry: H3K27me3 loss, H3K27M positivity). DNA methylation profiling (Illumina EPIC BeadArrays, brain tumour classifier (MNP v12.5 R package)) classified the tumour as ‘DMG, H3 K27-altered’ (calibrated score = 0.99). Further molecular studies (whole exome, whole genome sequencing) revealed concurrent H3.1 K27M and G34R mutations (clonal, in the same reads) of H3C3, FGF11 and PIK3CA somatic variants, and a pathogenic germline NBN variant. The RNAseq profile clustered with H3K27M-mutant tumours. A patient-derived cell culture was established enabling unbiased in vitro drug screening; no selective sensitivities were identified. Chromatin immunoprecipitation assays with sequencing (ChIP-seq; H3K27ac, H3K27me3, H3K36me3, RNApol2 marks) showed features in keeping with DMG H3 K27M-mutant tumours (H3K27ac loci including OLIG2, IRX1/2, PKDCC). The patient was treated with adjuvant radiotherapy, but progressed and passed away 13 months post-diagnosis. This case is an exceptionally rare, complex variant of histone-mutant paediatric HGG, illustrating that the H3.1 K27M mutation demonstrates a dominance over the molecular and clinical profiles compared to G34R, and highlights the importance of broad molecular profiling to identify such examples for further study.

Abstract AIMS To change the standard of care for collection of glial tumour tissue at a London teaching hospital. This would enable WGS on the tumour tissue, and give patients access to further clinical trials. METHOD The previous standard of care was for brain tumour pathology samples to be stored in paraffin. This was not suitable for WGS or for many clinical trials; the tumour samples needed to be sent to the lab as fresh tissue. The introduction of a genomics clinical nurse specialist meant that relationships were built between the surgical team, pathology teams and ward teams. There was a teaching by one of the neurosurgical team to the theatre staff. Genomics CNS led training for the nursing team. Adults started having WGS in May 2023 but many patient’s still had tissue incorrectly stored and could not have the sequencing performed. There was an introduction of a formal pathway in theatre created by one of the neurosurgeons in Dec 2023. RESULTS From May 2023 - November 2023, 58% adult glioma patients had WGS. Since December 2023 - current (March 2023) and the introduction of the formal pathways, 71% had WGS. CONCLUSION A formal pathway has now changed the standard of care for collecting tissue. There is still not 100% compliance, and this remains multifactorial. However the introduction of a formal pathway has now increased the percentage of eligible patients receiving WGS. This positive outcome has now led to discussions about freezing the fresh glioma tissue to allow glioma patient’s wider access to clinical trials which they would previously not have had access to.