Brain Tumor Pathology

Next-generation whole exome sequencing of glioblastoma with a primitive neuronal component Abstract Glioblastoma with a primitive neuronal component (GBM-PN) was renamed from glioblastoma with primitive neuroectodermal tumor-like component (GBM-PNET) in the new WHO classification of tumors of the central nervous system in 2016. GBM-PN is a rare variant of glioblastoma. There were not so many publications on the investigation of GBM-PN. We did whole exome sequencing for 11 GBM-PN cases and found that the percentage of TP53, PIK3CA, PIK3R1, or PTEN mutation in our GBM-PN cases (72.7%, 27.3%, 27.3%, and 27.3% respectively) was much higher than that in cases in TCGA GBM 2008, TCGA GBM 2013, and TCGA lower-grade glioma databases. The findings indicate that GBM-PN is a distinct variant of glioblastoma. The next-generation sequencing can play a role in the diagnosis of GBM-PN especially for small biopsy cases. Eight out of 11 cases showed mutations in PTEN–PI3K pathway, which indicates that targeted therapeutic agents (PI3K inhibitors, mTORC1 inhibitors or dual PI3K/mTOR inhibitors) may be used for the treatment of GBM-PN in the future.

MN1 rearrangement in astroblastoma: study of eight cases and review of literature Abstract Astroblastomas are unique tumours with unresolved issues in terms of their origin, molecular biology, clinical behaviour, and response to treatment. To decipher the characteristics of this tumour, we reviewed cases histologically diagnosed as astroblastoma in our institute over the past 8 years, with immunohistochemistry, and performed fluorescence in situ hybridisation (FISH), for the newly emerged MN1 rearrangement which was reported in central nervous system high-grade neuroepithelial tumours. The mean age at diagnosis was 18.6 years with all cases seen in females and with supratentorial localisation. The tumours showed typical circumscription and bubbly appearance on imaging. The cohort included eight cases diagnosed as astroblastoma (two low grades; six anaplastic) based on histology and proliferative index. The tumours displayed characteristic astroblastic pseudorosettes with hyalinised vascular core and variable immunopositivity for glial fibrillary acidic protein, pan cytokeratin, and epithelial membrane antigen. MN1 break-apart by FISH was found in 5/8 of our cases (62.5%), which included 2 low-grade and 3 anaplastic tumours. Tumour recurrence was noted in three cases, with MN1 alteration in two. We account for one of the few series to study the MN1rearrangement in astroblastoma and conclude that MN1 alteration is seen in a subset of these tumours.

Clinicopathological characteristics of circumscribed high-grade astrocytomas with an unusual combination of BRAF V600E, ATRX , and CDKN2A/B alternations Abstract We report four cases of high-grade astrocytoma with a BRAF V600E mutation, ATRX inactivation, and CDKN2A/B homozygous deletion. Children to young adults aged 3–46 presented with a well demarcated contrast-enhancing mass in the supratentorial area. Pathological examination revealed packed growth of short spindle to round polygonal cells including some pleomorphic cells. The tumors had less ability to infiltrate into the adjacent brain parenchyma and presented a circumscribed growth pattern. Mitosis was readily found, accompanied by focal necrosis and/or microvascular proliferation. Tumors were histologically similar in part to pleomorphic xanthoastrocytoma (PXA) or anaplastic PXA, but did not fit criteria for either neoplasm. A BRAF V600E mutation and homozygous deletion of CDKN2A/B were observed, which is similar to the genetic features of PXA or epithelioid glioblastoma, but the additional loss of ATRX nuclear immunoreactivity and absence of TERT promoter mutation were unusual findings, indicating a novel genetic profile. Despite their malignant histological features, all patients had a favorable clinical course and remained alive for 6 months to 28 years under standard medical treatment for malignant glioma. In summary, high grade astrocytomas with BRAF V600E, ATRX, and CDKN2A/B alternations had unique clinicopathological features and may be a novel subset of high grade glioma.

High-grade glioneuronal tumor with an ARHGEF2 – NTRK1 fusion gene Abstract Here, we report a highly unusual case of high-grade glioneuronal tumor with a neurotrophic tropomyosin receptor kinase (NTRK) fusion gene. A 13-year-old girl presented with headache and vomiting and MRI detected two cystic lesions bilaterally in the frontal areas with surrounding edema. The left larger tumor was removed by left frontal craniotomy. The tumor was diagnosed as a high-grade glioneuronal tumor, unclassified. Methylation profiling classified it as a diffuse leptomeningeal glioneuronal tumor (DLGNT) with low confidence. This tumor showed genotypes frequently found in DLGNT such as 1p/19q codeletion without IDH mutation and, however, did not have the typical DLGNT clinical and histological features. RNA sequencing identified an ARHGEF2 (encoding Rho/Rac guanine nucleotide exchange factor 2)–NTRK1 fusion gene. The presence of recurrent NTRK fusion in glioneuronal tumors has an important implication in the clinical decision making and opens up a possibility of novel targeted therapy.

A long-term survivor of pediatric midline glioma with H3F3A K27M and BRAF V600E double mutations Abstract We report a case of 2-year-old female with lateral ventricular glioma harboring both H3F3A K27M and BRAF V600E mutations. By the methylation analysis, the tumor was classified as a diffuse midline glioma H3 K27M mutant, WHO grade IV. However, the tumor was pathologically low-grade and likely localized rather than diffusely infiltrating. Further, the patient has survived more than 8 years after gross total resection of the tumor. Whereas both H3F3A K27M and BRAF V600E have been reported as poor prognostic markers in pediatric glioma, our case, along with several other reported cases, suggests that the coexistence of these two mutations might not indicate poor prognosis. The case emphasizes the importance of comprehensive assessment based on pathological, genetic and clinical findings and calls for further investigations of non-diffuse glioma with H3F3A K27M and glioma with H3F3A K27M and BRAF V600E.

Reviewers in 2018

Preface

Pilomyxoid astrocytomas: a short review Abstract Pilomyxoid astrocytoma is a variant of pilocytic astrocytoma and the clinical, histological and molecular data point to a very close relationship as well as a more aggressive biological behavior for the former. WHO 2016 classification does not provide a specific grade for these neoplasms, but there is sufficient evidence in the literature that pilomyxoid astrocytoma has slightly worse prognosis than typical pilocytic astrocytoma. There is increasing evidence that in addition to the MAPK pathway alterations, pilomyxoid astrocytomas harbor genetic alterations that distinguish them from typical pilocytic astrocytoma

Pathologic and molecular aspects of anaplasia in circumscribed gliomas and glioneuronal tumors Abstract Many breakthroughs have been made in the past decade regarding our knowledge of the biological basis of the diffuse gliomas, the most common primary central nervous system (CNS) tumors. These tumors as a group are aggressive, associated with high mortality, and have a predilection for adults. However, a subset of CNS glial and glioneuronal tumors are characterized by a more circumscribed pattern of growth and occur more commonly in children and young adults. They tend to be indolent, but our understanding of anaplastic changes in these tumors continues to improve as diagnostic classifications evolve in the era of molecular pathology and more integrated and easily accessible clinical databases. The presence of anaplasia in pleomorphic xanthoastrocytomas and gangliogliomas is assigned a WHO grade III under the current classification, while the significance of anaplasia in pilocytic astrocytomas remains controversial. Recent data highlight the association of the latter with aggressive clinical behavior, as well as the presence of molecular genetic features of both pilocytic and diffuse gliomas, with the recognition that the precise terminology remains to be defined. We review the current concepts and advances regarding histopathology and molecular understanding of pilocytic astrocytomas, pleomorphic xanthoastrocytomas, and gangliogliomas, with a focus on their anaplastic counterparts.

Overview of DNA methylation in adult diffuse gliomas Abstract Adult diffuse gliomas form a heterogeneous group of tumors of the central nervous system that vary greatly in histology and prognosis. A significant advance during the last decade has been the identification of a set of genetic lesions that correlate well with histology and clinical outcome in diffuse gliomas. Most characteristic driver mutations consist of isocitrate dehydrogenase 1 (IDH1) and IDH2, and H3 histone family member 3A, which are strongly associated with DNA and histone methylation patterns. A well-characterized DNA methylation aberration is on the O6-methylguanine-DNA methyltransferase promoter. This aberration is associated with an improved response to the DNA alkylating agent, temozolomide. Methylation alterations are used for classification or treatment decisions of diffuse gliomas. This supports the importance of considering epigenomic aberrations in the pathogenesis of gliomas. Recent DNA methylation analyses revealed a small group of IDH mutant diffuse gliomas exhibiting decreased DNA hypermethylation resulting in substantial unfavorable prognosis comparable to glioblastoma. Thus, DNA methylation patterns may become a new standard that replaces the conventional grading system based on histological diagnosis. In this review, we summarize recent developments regarding the contributions of methylation patterns to the pathogenesis of adult diffuse glioma, the interactions between methylation patterns and driver mutations, and potential epigenomic targeted therapies.

Alexandros Sfakianakis
Anapafseos 5 . Agios Nikolaos
Crete.Greece.72100
2841026182

6948891480

alsfakia@gmail.com