Quezado, Martha

Abstract Background Rare pediatric and young adult brain tumors pose major diagnostic and therapeutic challenges due to limited evidence and scattered expertise. The International Rare Brain Tumor Board was established to enable multidisciplinary case review, shared learning, and collaborative decision support. Methods Launched in February 2025, the Rare Brain Tumor Board is a monthly collaborative initiative led by Children’s National Hospital and the National Institutes of Health (NIH). Close partnership with the European Pediatric Rare CNS Tumor Board enhances transatlantic exchange and alignment of diagnostic and treatment recommendations. De-identified cases are presented with clinical history, neuroimaging, histopathology, and molecular profiling, including DNA methylation classification, available for the majority of cases. Sessions are structured to support integrated diagnosis and evidence-informed management recommendations through multidisciplinary discussion (neuropathology, neuroradiology, neurosurgery, radiation oncology, and pediatric as well as adult neuro-oncology). Findings Since its inception, 12 sessions have been held averaging 138 participants per session, reviewing a total of 32 cases (mean 3 cases/session; range 1–4) from 7 different countries and 3 different continents. Entities reviewed include DICER1-intracranial sarcoma (n = 5), astroblastoma (n = 4), FOXR2-activated neuroblastoma (n = 4), CNS tumors with BCOR internal tandem duplication (n = 3) and, BCOR-fused tumors (n = 3), CIC-rearranged-sarcoma (n = 3), intracranial mesenchymal tumor FET::CREB fusion positive (n = 3), MN1::PATZ1 fusion tumors (n = 2), undifferentiated sarcoma (n = 2), PLAG1-fusion tumor (n = 1), medullomyoblastoma (n = 1), and EZHIP-altered diffuse midline glioma (DMG) (n = 1). Multidisciplinary review has supported diagnostic clarification, strengthened familiarity with ultra-rare entities, and informed real-world treatment discussions in settings where prospective data are limited. Discussions have also increased awareness of rare brain tumor registries and opportunities for systematic case capture. Conclusion An international multidisciplinary rare brain tumor board is a feasible, scalable model to advance integrated diagnosis and collaborative management of ultra-rare pediatric and young adult brain tumors, while building a shared knowledge base across institutions.

Abstract Background Approximately 12,000 adolescents and young adults (ages 15-39, AYAs) are diagnosed with a primary central nervous system (CNS) tumor each year. DNA methylation profiling has transformed CNS tumor classification by refining diagnostic accuracy and identifying biologically distinct subtypes, but its application has not been systematically evaluated in the AYA population. In this study, we examined the spectrum of CNS tumor types across age groups, with a focus on the AYA population. Methods We assembled a large dataset of CNS tumor samples with age annotations and methylation profiles matching with high confidence to a CNS tumor type using the NCI/Bethesda classifier. Prevalence of tumor type, methylation class and DNA copy number aberrations were compared across age strata (pediatric, AYA and adult). Results The cohort of 21,099 CNS tumors included 5139 tumors from AYAs (24%), which showed a mixed pattern, with tumors typical of childhood (e.g. medulloblastoma) as well as those common in older adults (e.g. glioblastoma). Several tumor types were specifically enriched in the AYA, including IDH-mutant astrocytoma, pleomorphic xanthoastrocytoma, posterior fossa group B ependymoma, and diffuse hemispheric glioma, H3 G34-mutant, among others. Distinct methylation subclasses of multiple tumor types were observed in the AYA, and patterns of genomic aberrations showed age-specific distributions. Conclusion Large-scale methylation profiling revealed unique classification patterns of CNS tumors in AYAs, with specific tumor types, subclasses, and genomic alterations enriched in this population. These data may serve as a valuable reference resource for better understanding the spectrum of CNS tumors affecting AYA patients.

Abstract Computer vision now enables deep learning models to link histopathologic features to molecular features in a quantitative manner not previously achievable by human pathologists. However, human interpretability is often limited. We trained a deep neural network to predict gene expression from digital whole slide images (WSIs) using 848 central nervous system (CNS) tumors with paired WSI and RNA-sequencing data. We used inferred RNA expression levels as a surrogate for protein expression of the CNS tumor lineage markers GFAP, OLIG2, and SSTR2, as well as the proliferation marker MKI67 (Ki67). We established thresholds for categorizing the inferred expression levels as positive or negative based on levels observed in cross-validation testing in select tumor types to approximate routine clinical interpretation of immunohistochemical (IHC) staining. We tested the sensitivity and specificity of our ‘virtual’ IHC on an independent, multi-institutional cohort of over 2,000 CNS tumors with objective diagnostic labels derived from DNA methylation-based tumor classification. As a dichotomous variable, inferred GFAP expression showed a sensitivity of 74% and a specificity of 99% as a glial marker in a cohort of gliomas and meningiomas. In the same cohort, OLIG2 showed a sensitivity of 75% and a specificity of 97% as a glial marker, while SSTR2 showed a sensitivity of 83% and a specificity of 97% as a marker of meningioma. In a cohort of ependymomas and gliomas, virtual IHC for OLIG2 showed a sensitivity of 75% and a specificity of 82% in distinguishing ependymomas from gliomas. Finally, in a cohort of gliomas, inferred expression of MKI67 demonstrated a trend consistent with what would be expected by actual IHC, with increasing MKI67 expression with increasing tumor grade. Our model provides the basis for a human interpretable and clinically applicable deep neural network to aid human pathologists in the diagnosis and grading of CNS tumors.

Abstract Adult primary leptomeningeal gliomatosis (PLG) is a rare, rapidly progressive and fatal disease characterized by prominent leptomeningeal infiltration by a glial tumor without an identifiable parenchymal mass. The molecular profile of adult PLG has not been well‐characterized. We report the clinical, pathological, and molecular findings of six adult PLG patients (five males and one female), median age 58 years. All cases exhibited pathological leptomeningeal enhancement at presentation. Leptomeningeal biopsy was diagnostic in five (of six) cases, revealing infiltration by an astrocytic glioma with mitotic activity, lacking microvascular proliferation or necrosis. One case was diagnosed at autopsy. All tumors were IDH‐wildtype, with five harboring TERT promoter mutations. Additional mutations identified were PTEN in one case, TP53 in two cases, and NF1 in two cases. A chromosome profile with +7/−10 was found in four cases, whereas the remaining two showed either chromosome 7 or 7p gain only. Four cases showed chromosome 9p loss with CDKN2A/B homozygous deletion, one case showed hemizygous CDKN2A/B loss, and one case showed intact chromosome 9 and CDK4/GLI1 amplification. DNA methylation profiling was performed in four cases and revealed a match to glioblastoma (GBM) family and mesenchymal typical class with high confidence scores in two cases; the other two cases showed only suggestive combined scores for GBM family and mesenchymal atypical class. The molecular profile of all cases closely aligned with that of adult‐type GBM, IDH‐wildtype, CNS WHO grade 4. All patients succumbed to the disease. In five cases with extensive leptomeningeal disease at diagnosis, the course was rapid, with median survival of 24 days following palliative care. Only one case, with relatively localized disease at diagnosis, received chemoradiation therapy and survived 535 days, raising the possibility that early diagnosis and timely treatment could improve outcome. A detailed list of previously reported cases is provided in a supplementary table.

Abstract Methylation profiling has revealed unexpected relationships between traditional histopathology-based versus biologically-based classifications of brain tumors. Methylation class pleomorphic xanthoastrocytoma (mcPXA) comprises tumors with the same methylation signature as classical PXA but with additional morphologic patterns, including overlap with glioblastoma (GBM). To characterize mcPXA, we examined epidemiologic, histologic, and molecular features as well as clinical behavior of a cohort (n=313) of tumors matching to mcPXA by the DKFZ classifier (v12 score >= 0.85). Patient median age was 19 (range 1-73) with a female predominance (178 female/135 male). CDKN2A/B homozygous deletion was observed in 273 (87%) cases. In the subset of cases tested for BRAF p.V600E (n=120), 111 (93%) harbored the mutation. Concomitant chr7+/chr10- was observed in 66 (21%) cases. In the subset of cases tested for TERT promoter mutations (n=50), 11 (22%) harbored the mutation, always with co-occurrence of BRAF p.V600E (11/11) and infrequently with chr7+/chr10- (3/11). MGMT promoter methylation was observed in 40 (13%) cases. Overall and progression-free survival (OS, PFS) in mcPXA were similar to grade 2-3 IDH-mutant astrocytoma (A-IDH). Prognostic factors in mcPXA included GBM-like histopathology (defined as cases diagnosed as GBM prior to methylation profiling), concomitant chr7+/chr10-, and MGMT promoter methylation. GBM-like histopathology was associated with shorter OS (p=0.02) and PFS (p< 0.01) compared to cases without GBM-like histopathology. Concomitant chr7+/chr10- was associated with shorter PFS (p=0.02), and MGMT promoter methylation was associated with shorter OS (p=0.03). Our findings demonstrate that mcPXA tumors affect adolescents and young adults, share molecular features of classical PXA, and manifest clinical behavior similar to classical PXA, but subsets of tumors with atypical features (chr7+/chr10-, MGMT promoter methylation, and/or GBM-like histopathology) are more aggressive. The use of a molecular definition of PXA reveals that this tumor type is more common than previously appreciated and warrants in-depth study for therapeutic options.