Lebrun et al. Acta Neuropathologica Communications (2020) 8:128 https://doi.org/10.1186/s40478-020-00962-1 RESEARCH Open Access Clinical, radiological and molecular characterization of intramedullary astrocytomas Laetitia Lebrun1 , Barbara Meléndez1,2, Oriane Blanchard1, Nancy De Nève1, Claude Van Campenhout1, Julie Lelotte3, Danielle Balériaux4, Matteo Riva5, Jacques Brotchi6, Michaël Bruneau6, Olivier De Witte6, Christine Decaestecker7,8, Nicky D’Haene1 and Isabelle Salmon1,7* Abstract Intramedullary astrocytomas (IMAs) are rare tumors, and few studies specific to the molecular alterations of IMAs have been performed. Recently, KIAA1549-BRAF fusions and the H3F3A p.K27M mutation have been described in low-grade (LG) and high-grade (HG) IMAs, respectively. In the present study, we collected clinico-radiological data and performed targeted next-generation sequencing for 61 IMAs (26 grade I pilocytic, 17 grade II diffuse, 3 LG, 3 grade III and 12 grade IV) to identify KIAA1549-BRAF fusions and mutations in 33 genes commonly implicated in gliomas and the 1p/19q regions. One hundred seventeen brain astrocytomas were analyzed for comparison. While we did not observe a difference in clinico-radiological features between LG and HG IMAs, we observed significantly different overall survival (OS) and event-free survival (EFS). Multivariate analysis showed that the tumor grade was associated with better OS while EFS was strongly impacted by tumor grade and surgery, with higher rates of disease progression in cases in which only biopsy could be performed. For LG IMAs, EFS was only impacted by surgery and not by grade. The most common mutations found in IMAs involved TP53, H3F3A p.K27M and ATRX.As in the brain, grade I pilocytic IMAs frequently harbored KIAA1549-BRAF fusions but with different fusion types. Non- canonical IDH mutations were observed in only 2 grade II diffuse IMAs. No EGFR or TERT promoter alterations were found in IDH wild-type grade II diffuse IMAs. These latter tumors seem to have a good prognosis, and only 2 cases underwent anaplastic evolution. All of the HG IMAs presented at least one molecular alteration, with the most frequent one being the H3F3A p.K27M mutation. The H3F3A p.K27M mutation showed significant associations with OS and EFS after multivariate analysis. This study emphasizes that IMAs have distinct clinico-radiological, natural evolution and molecular landscapes from brain astrocytomas. Keywords: Intramedullary astrocytomas-glial tumor-spinal cord-targeted next-generation sequencing-H3F3A K27M- KIAA1549-BRAF * Correspondence: [email protected] 1Department of Pathology, Erasme University Hospital, Université Libre de Bruxelles (ULB), 808 Route de Lennik, B-1070 Brussels, Belgium 7DIAPath, Center for Microscopy and Molecular Imaging, ULB, Gosselies, Belgium Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Lebrun et al. Acta Neuropathologica Communications (2020) 8:128 Page 2 of 14 Introduction following inclusion criteria were defined: pathological The recently updated 4th edition of the World Health diagnosis of LG or HG astrocytoma and spine location. Organization (WHO) Classification of Central Nervous We excluded cases with a secondary supratentorial loca- System (CNS) tumors in 2016 (WHO 2016) drastically tion at diagnosis. Pathological diagnosis was reviewed by changed histological diagnosis in neuropathology by in- two neuropathologists (LL and IS) according to the tegrating molecular data into daily diagnostic practice WHO 2016 classification [30]. According to the [30, 51]. The current WHO 2016 classification of CNS cIMPACT-NOW (the Consortium to Inform Molecular tumors is based on clinical criteria, histology and mo- and Practical Approaches to CNS Tumor Taxonomy) lecular characteristics to achieve accurate determination Update 4, the presence of the KIAA1549-BRAF fusion of the prognosis and response to treatment and to im- gene led to grade I pilocytic astrocytoma diagnosis in prove patient management [30]. The WHO 2016 classifi- cases for which a differential diagnosis between grade I cation is applied using the same criteria for supra- pilocytic and grade II diffuse astrocytomas could not be tentorial, infra-tentorial, posterior fossa and intramedul- made [13]. Grade III astrocytoma diagnosis was based lary gliomas, regardless of location. However, the vast on mitotic activity, high cellularity, nuclear atypia with- majority of molecular data on gliomas were obtained out features of glioblastoma (necrosis and microvascular from studies of tumors localized in the brain [5, proliferation). To note, for the three grade III astrocyto- 50].Some studies, however, have shown that particular mas, as surgical resection was not complete according to molecular alterations are related to tumor location. Fu- surgical reports, we could not exclude undersampled sions involving the BRAF and KIAA1549 genes are found glioblastoma. The final cohort consisted of 61 patients in nearly 80% of cerebellar grade I astrocytomas but only with IMAs diagnosed between 1989 and 2019 from 50–55% of non-cerebellar grade I cases [24]. Similarly, Erasme and Saint-Luc University Hospital. Twenty-six of the p.K27M somatic mutation in the H3F3A gene the tumors were grade I pilocytic astrocytomas, 17 were (H3K27M) [41] predominates in high-grade (HG) infil- grade II diffuse astrocytomas, 3 were grade III astrocyto- trative astrocytomas in midline locations, mainly the mas and 12 grade IV astrocytomas. Three cases were brain stem, thalamus and spinal cord [44]. ruled LG astrocytomas because no diagnosis of grade I Only a few studies specifically addressing intramedul- or grade II could be made. To compare the molecular lary gliomas are available. Intramedullary tumors are profile of this cohort of IMAs with their brain counter- rare CNS neoplasms accounting for 2 to 4% of all CNS parts, we used a set of 117 samples obtained from astro- tumors [41, 48]. The majority of these (80%) are gliomas, cytoma patients consecutively diagnosed between 2017 which are ependymomas (60–70%) and astrocytomas and 2019 that were not located in spine and that were (30–40%) [4]. analyzed by next-generation sequencing (NGS) in our The few available studies specific to the molecular alter- daily practical routine diagnosis setting using gene- ations of intramedullary astrocytomas (IMAs) have been targeted “clinical glioma” and “KIAA1549-BRAF fusion” performed and have shown that the most frequent recur- panels (see below). This series included 16 grade I astro- rent molecular alterations are fusions involving cytomas, 13 grade II astrocytomas, 13 grade III astrocy- KIAA1549-BRAF and H3K27M mutations [41]. To date, tomas and 75 grade IV astrocytomas. very few cases with IDH mutations have been described in Magnetic resonance imaging (MRI) exams were IMAs, and these mutations were not classic IDH1 reviewed for available cases (n = 34) by an expert neuro- p.R132H and IDH2 p.R172H mutations [9, 12, 41, 47, 54]. radiologist (DB). For the remaining cases, imaging fea- Nevertheless, while the genetic profiles of brain astro- tures were collected from MRI reports. The imaging cytomas have been largely established, those of uncom- features assessed were location, signal T1 and T2 inten- mon IMAs remain to be defined. The present study sity, contrast enhancement, well-delineated vs. infiltra- aimed to correlate clinical, radiological and molecular tive pattern, cystic component and necrosis. Figure 1 data of IMAs to improve the current knowledge about illustrates representative radiological and pathological the prognosis and molecular profile of these tumors. features of IMAs. Clinical variables were collected based on clinical and Materials and methods surgical reports: age, gender, extent of surgery (biopsy, Patient cohort partial or total resection), adjuvant treatments, follow-up Institutional Review Board approval for a retrospective duration and survival status. Based on MRI reports (con- analysis of archival biobank tissue was obtained from trast enhancement and/or tumor size increase), event-free Biobanque Hôpital Erasme-ULB (BERA), BE_NBWB1, survival (EFS) was assessed as the time until recurrence Biothèque Wallonie Bruxelles (BWB), BBMRI-ERIC) and after gross total resection or disease progression after bi- Biolibrary of Saint-Luc University Hospital, together opsy/partial resection, as defined by Pekmezci et al. [34] with ethical agreement. For