Giannini, Caterina

Abstract Purpose: Glioblastoma is the most frequent and lethal primary brain tumor. Development of novel therapies relies on the availability of relevant preclinical models. We have established a panel of 96 glioblastoma patient-derived xenografts (PDX) and undertaken its genomic and phenotypic characterization. Experimental Design: PDXs were established from glioblastoma, IDH-wildtype (n = 93), glioblastoma, IDH-mutant (n = 2), diffuse midline glioma, H3 K27M-mutant (n = 1), and both primary (n = 60) and recurrent (n = 34) tumors. Tumor growth rates, histopathology, and treatment response were characterized. Integrated molecular profiling was performed by whole-exome sequencing (WES, n = 83), RNA-sequencing (n = 68), and genome-wide methylation profiling (n = 76). WES data from 24 patient tumors was compared with derivative models. Results: PDXs recapitulate many key phenotypic and molecular features of patient tumors. Orthotopic PDXs show characteristic tumor morphology and invasion patterns, but largely lack microvascular proliferation and necrosis. PDXs capture common and rare molecular drivers, including alterations of TERT, EGFR, PTEN, TP53, BRAF, and IDH1, most at frequencies comparable with human glioblastoma. However, PDGFRA amplification was absent. RNA-sequencing and genome-wide methylation profiling demonstrated broad representation of glioblastoma molecular subtypes. MGMT promoter methylation correlated with increased survival in response to temozolomide. WES of 24 matched patient tumors showed preservation of most genetic driver alterations, including EGFR amplification. However, in four patient–PDX pairs, driver alterations were gained or lost on engraftment, consistent with clonal selection. Conclusions: Our PDX panel captures the molecular heterogeneity of glioblastoma and recapitulates many salient genetic and phenotypic features. All models and genomic data are openly available to investigators.

Objective. We explore the clinicopathologic features of Ewing sarcoma (ES) presenting in older adulthood. Methods. Cases of molecularly confirmed ES arising in patients aged ≥40 years were evaluated. Results. Fifty patients were identified (33 males/17 females; 41-86 years). The majority of tumors (41) arose at extraskeletal sites, while 9 were bone primaries. Twenty-eight cases showed nested architecture, while the remaining cases showed sheet-like growth. Tumor cytology was categorized as conventional (n = 39), crushed (n = 5), clear cell (n = 4), rhabdoid (n = 3), and epithelioid (n = 2). Fifty percent had necrosis, while rosettes were noted in 1 case. Immunostains performed ranged from 1 to 28 (median = 10). Follow-up (n = 43, 1-147 months) revealed 15 patients with metastasis. Conclusion. Although rare, ES should be considered in the differential diagnosis for round cell malignancies in older adult patients. In this cohort, ES is most often extraskeletal, and may show unusual morphologic features, closely simulating more common neoplasms in this age group.

Abstract Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a recently described epileptogenic tumor characterized by oligodendroglioma-like components, aberrant CD34 expression, and genetic MAPK pathway activation through alterations such as BRAF V600E mutation, and FGFR2-KIAA1598/CTNNA3 and FGFR3-TACC3 fusions. We report the molecular profiling of PLNTY in 9 patients, 7 female: 2 male, median age at diagnosis of 16 years (range, 5–34). All tumors were supratentorial with diagnostic morphological features of PLNTY including oligodendroglioma-like areas and strong diffuse CD34 immunostaining. Four (of 9; 44%) tumors were positive for BRAF V600E immunostain, indicating the presence of a BRAF V600E mutation. The 6 cases evaluated for IDH status were negative by IDH1-R132H immunostain (n=5; 3 BRAF V600E-negative and 2 BRAF V600E-positive) or by NGS (n=1; BRAF V600E-negative). Oncoscan chromosomal microarray performed in 5 BRAF V600E-negative tumors showed recurrent copy number changes including gain of whole chromosomes 5, 7, 8, 9, 12, 18, 19, 20, 21 and X, and loss of chromosomes 1, 2, 10q, 13, 22 and Xq. The 10q losses (n=2) were highly suggestive of an FGFR2-KIAA1598 and of a potentially novel FGFR2 underlying fusion event in one case each. Custom targeted neuro-oncology DNA and RNA NGS panel performed in 2 cases revealed a fusion similar to fusions previously reported in pilocytic astrocytoma: one with a KIAA1549-BRAF (exon 15-exon 9) fusion associated with a 7q34 ~785 kilobase deletion rather than the characteristic ~2 megabase duplication seen in pilocytic astrocytoma, and another with a QKI-NTRK2 (exon 6-exon 15) fusion associated with a 9q21 ~191 kilobase duplication disrupting NTRK2. The KIAA1549-BRAF fusion-positive case also had a TP53 mutation with loss of whole chromosome 17, suggesting TP53 complete inactivation. This study confirms that PLNTY is a low-grade neuroepithelial tumor with frequent MAPK pathway activation and expands the spectrum of MAPK activating alterations observed in PLNTY.

Abstract BACKGROUND Oligodendrogliomas are classified as either WHO grade II or III depending on histologic features. Grade often influences treatment decisions. However, there is variability in patient outcome within tumors of similar grade. We hypothesized that copy number burden (CNB) and specific copy number variants (CNV) might be associated with oligodendroglioma grade and prognosis. METHODS Copy number array analyses were performed on 285 molecular oligodendrogliomas (IDH-mutant, 1p/19q-whole arm-codeleted) from the Mayo Clinic internal and consult neuropathology practice and 167 TCGA molecular oligodendrogliomas. CNB was defined as the total number of copy number alterations. The association of CNB and CNV with grade and overall survival (when available) was assessed. All Mayo and TCGA data were evaluated using the ChAS software suite (Thermo- Fisher) and blindly reviewed by a clinical cytogeneticist (RBJ). RESULTS The mean CNB was 5.0 and 10.4 in the Mayo WHO grade II and III oligodendrogliomas, respectively (p = 5.4 x 10–17). Among the TCGA WHO grade II and III oligodendrogliomas the mean CNB was 4.4 and 5.3, respectively (p = 0.034). Common CNVs (occurring in at least 5% of cases) were -4/4q-, +8/8q+, -9/9p-/cnLOH 9p, +11/11q+, -14/14q-, -15 and -18/18q-. Of these, -9/9p-/cnLOH 9p was significantly associated with higher grade in both the Mayo and TCGA cohorts (p = 8.3 x 10-10 and 0.018, respectively). In the TCGA cohort the presence of >10 CNVs or +11/11q+ was associated with a poorer survival (p = 0.016 and 0.006, respectively). CONCLUSIONS CNB is significantly associated with WHO grade in IDH-mutant, 1p/19q co-deleted oligodendrogliomas. The presence of a significantly elevated CNB in some WHO grade II tumors may be suspicious for the presence of unappreciated grade III histologic features. Longer follow-up will be necessary to determine if CNB or single CNVs are associated with survival.

The specific effect of TDP-43 pathology on grey matter volume in individuals without frontotemporal lobar degeneration is unclear. Bejanin et al. reveal a major and independent contribution of TDP-43 to neurodegeneration and shed light on the regional distribution of TDP-43-related atrophy in older adults.

AimsCellular schwannoma is a specific subtype of schwannoma, prone to misinterpretation as a malignant neoplasm. Involvement of the intracranial compartment by these tumours is extremely rare. We aim to characterise this clinicopathological subgroup.Methods and resultsWe identified a total of 20 cellular schwannomas with predominant intracranial involvement. The mean age of the patients at the time of surgery was 37 years (range = 16–81), with a slight female predominance (1.5:1 ratio). The most common sites were the eighth (n = 8) and fifth (n = 6) cranial nerves. Three tumours involved the anterior cranial fossa/olfactory groove, and a single case involved the glossopharyngeal nerve. All tumours met established criteria for cellular schwannoma, and were composed of interlacing fascicles of spindle cells lacking Verocay bodies with minimal Antoni B pattern and variable chronic inflammation and foamy histiocytes. Rare findings included haemosiderin deposition (n = 6), necrosis (n = 4), brisk mitotic activity (>10 mitoses per 10 high‐power fields) (n = 2), focal epithelioid morphology (n = 2), myxoid areas (n = 2), neuroblastoma‐like pattern (n = 1) and granular cells (n = 1). Immunohistochemical stains demonstrated expression of Schwann cell markers (S100 protein, SOX10, collagen IV) and preserved H3 K27 trimethylation in all cases tested. Fourteen patients had postoperative follow‐up, ranging from 2 months to 21 years (mean = 66 months). In patients with follow‐up, local recurrence/persistence developed in six cases; five tumours were initially incompletely resected. No metastatic disease or deaths were reported.ConclusionsIntracranial cellular schwannomas share morphological and immunophenotypical features with cellular schwannomas at others sites may demonstrate locally aggressive growth but appear to lack metastatic potential.

Abstract Adult spinal cord ependymomas are typically low grade and have a relatively favorable clinical course following gross total resection. We report 4 cases of anaplastic spinal cord ependymoma with MYCN amplification, an exceptionally rare finding. All cases occurred in the spinal cord of adolescent and young adult women and had morphological and immunohistochemical features of anaplastic ependymomas (World Health Organization grade III). Chromosomal microarray analysis demonstrated amplification of 2p24 (including MYCN) in all cases. One patient died 6 months after surgery. Another patient recently had removal of metastatic nodules in the thoracic region, following gross total resection and adjuvant radiation therapy of a lumbar ependymoma 1 year previously. One patient responded well after chemotherapy but died after multiple relapses 82 months after diagnosis. We found MYCN amplification reported in 2 other ependymomas, both anaplastic and arising in the spinal cord of adult females (Brain Pathol 2001;11:133–43). One patient had multiple recurrences in the spinal cord and an intracranial metastasis. Although MYCN amplification is rare in ependymomas, the current and previously reported cases suggest that this is associated with higher-grade histology, spinal location, and often unfavorable prognosis. The clinical significance and therapeutic implications of MYCN amplification in ependymomas require further evaluation.

AbstractCerebral amyloidomas, characterized by localized amyloid deposits in the nervous system in the absence of systemic disease, are rare. These typically consist of immunoglobulin light chain (AL)-type, predominantly lambda. Trigeminal nerve involvement is exceptionally rare with only 21 previously reported cases, three with bilateral disease. We report two additional cases of amyloid localized to Meckel’s cave with secondary involvement of the trigeminal nerves bilaterally, with protein characterization by mass spectrometry. The patients, both females, 39 and 49-years-old, respectively, presented with the insidious onset of progressive trigeminal neuropathy, including pain and numbness with sensory loss, refractory to medical therapy. One patient experienced bilateral symptoms. Magnetic resonance imaging demonstrated abnormal thickening and contrast enhancement along Meckel’s cave bilaterally in both cases. The clinical differential diagnosis included benign neoplasms and inflammatory disorders. At the time of biopsy, the trigeminal nerve was noted to be enlarged and multinodular in one case and associated with abnormal soft tan tissue in the other case. Microscopically, the nerve biopsies showed extensive Congo red-positive amyloid deposits. Liquid chromatography tandem mass spectrometry demonstrated that the amyloid was of (AL)-type in both cases (AL [kappa] in one case and AL [lambda] in the other). After extensive evaluation, there was no evidence of systemic involvement. Both patients received localized radiotherapy for their refractory symptoms. One patient has stable symptomatology and imaging. No follow-up is available for the other patient.