Concurrent ependymal and ganglionic differentiation in a subset of supratentorial neuroepithelial tumors with EWSR1-PLAGL1 rearrangement.

Neuroepithelial tumors with fusion of PLAGL1 or amplification of PLAGL1/PLAGL2 have recently been described often with ependymoma-like or embryonal histology respectively. To further evaluate emerging entities with PLAG-family genetic alterations, the histologic, molecular, clinical, and imaging features are described for 8 clinical cases encountered at St. Jude (EWSR1-PLAGL1 fusion n = 6; PLAGL1 amplification n = 1; PLAGL2 amplification n = 1). A histologic feature observed on initial resection in a subset (4/6) of supratentorial neuroepithelial tumors with EWSR1-PLAGL1 rearrangement was the presence of concurrent ependymal and ganglionic differentiation. This ranged from prominent clusters of ganglion cells within ependymoma/subependymoma-like areas, to interspersed ganglion cells of low to moderate frequency among otherwise ependymal-like histology, or focal areas with a ganglion cell component. When present, the combination of ependymal-like and ganglionic features within a supratentorial neuroepithelial tumor may raise consideration for an EWSR1-PLAGL1 fusion, and prompt initiation of appropriate molecular testing such as RNA sequencing and methylation profiling. One of the EWSR1-PLAGL1 fusion cases showed subclonal INI1 loss in a region containing small clusters of rhabdoid/embryonal cells, and developed a prominent ganglion cell component on recurrence. As such, EWSR1-PLAGL1 neuroepithelial tumors are a tumor type in which acquired inactivation of SMARCB1 and development of AT/RT features may occur and lead to clinical progression. In contrast, the PLAGL2 and PLAGL1 amplified cases showed either embryonal histology or contained an embryonal component with a significant degree of desmin staining, which could also serve to raise consideration for a PLAG entity when present. Continued compilation of associated clinical data and histopathologic findings will be critical for understanding emerging entities with PLAG-family genetic alterations.

Lee JC ，Koo SC ，Furtado LV ，Breuer A ，Eldomery MK ，Bag AK ，Stow P ，Rose G ，Larkin T ，Sances R ，Kleinschmidt-DeMasters BK ，Bodmer JL ，Willard N ，Gokden M ，Dahiya S ，Roberts K ，Bertrand KC ，Moreira DC ，Robinson GW ，Mo JQ ，Ellison DW ，Orr BA ... -  《Acta Neuropathologica Communications》

CNS tumors with PLAGL1-fusion: beyond ZFTA and YAP1 in the genetic spectrum of supratentorial ependymomas.

A novel methylation class, "neuroepithelial tumor, with PLAGL1 fusion" (NET-PLAGL1), has recently been described, based on epigenetic features, as a supratentorial pediatric brain tumor with recurrent histopathological features suggesting an ependymal differentiation. Because of the recent identification of this neoplastic entity, few histopathological, radiological and clinical data are available. Herein, we present a detailed series of nine cases of PLAGL1-fused supratentorial tumors, reclassified from a series of supratentorial ependymomas, non-ZFTA/non-YAP1 fusion-positive and subependymomas of the young. This study included extensive clinical, radiological, histopathological, ultrastructural, immunohistochemical, genetic and epigenetic (DNA methylation profiling) data for characterization. An important aim of this work was to evaluate the sensitivity and specificity of a novel fluorescent in situ hybridization (FISH) targeting the PLAGL1 gene. Using histopathology, immunohistochemistry and electron microscopy, we confirmed the ependymal differentiation of this new neoplastic entity. Indeed, the cases histopathologically presented as "mixed subependymomas-ependymomas" with well-circumscribed tumors exhibiting a diffuse immunoreactivity for GFAP, without expression of Olig2 or SOX10. Ultrastructurally, they also harbored features reminiscent of ependymal differentiation, such as cilia. Different gene partners were fused with PLAGL1: FOXO1, EWSR1 and for the first time MAML2. The PLAGL1 FISH presented a 100% sensitivity and specificity according to RNA sequencing and DNA methylation profiling results. This cohort of supratentorial PLAGL1-fused tumors highlights: 1/ the ependymal cell origin of this new neoplastic entity; 2/ benefit of looking for a PLAGL1 fusion in supratentorial cases of non-ZFTA/non-YAP1 ependymomas; and 3/ the usefulness of PLAGL1 FISH.

Tauziède-Espariat A ，Nicaise Y ，Sievers P ，Sahm F ，von Deimling A ，Guillemot D ，Pierron G ，Duchesne M ，Edjlali M ，Dangouloff-Ros V ，Boddaert N ，Roux A ，Dezamis E ，Hasty L ，Lhermitte B ，Hirsch E ，Hirsch MPV ，Ardellier FD ，Karnoub MA ，Csanyi M ，Maurage CA ，Mokhtari K ，Bielle F ，Rigau V ，Roujeau T ，Abad M ，Klein S ，Bernier M ，Horodyckid C ，Adam C ，Brandal P ，Niehusmann P ，Vannod-Michel Q ，Provost C ，de Champfleur NM ，Nichelli L ，Métais A ，Mariet C ，Chrétien F ，Blauwblomme T ，Beccaria K ，Pallud J ，Puget S ，Uro-Coste E ，Varlet P ，RENOCLIP-LOC ... -  《Acta Neuropathologica Communications》

Recurrent fusions in PLAGL1 define a distinct subset of pediatric-type supratentorial neuroepithelial tumors.

Ependymomas encompass a heterogeneous group of central nervous system (CNS) neoplasms that occur along the entire neuroaxis. In recent years, extensive (epi-)genomic profiling efforts have identified several molecular groups of ependymoma that are characterized by distinct molecular alterations and/or patterns. Based on unsupervised visualization of a large cohort of genome-wide DNA methylation data, we identified a highly distinct group of pediatric-type tumors (n = 40) forming a cluster separate from all established CNS tumor types, of which a high proportion were histopathologically diagnosed as ependymoma. RNA sequencing revealed recurrent fusions involving the pleomorphic adenoma gene-like 1 (PLAGL1) gene in 19 of 20 of the samples analyzed, with the most common fusion being EWSR1:PLAGL1 (n = 13). Five tumors showed a PLAGL1:FOXO1 fusion and one a PLAGL1:EP300 fusion. High transcript levels of PLAGL1 were noted in these tumors, with concurrent overexpression of the imprinted genes H19 and IGF2, which are regulated by PLAGL1. Histopathological review of cases with sufficient material (n = 16) demonstrated a broad morphological spectrum of tumors with predominant ependymoma-like features. Immunohistochemically, tumors were GFAP positive and OLIG2- and SOX10 negative. In 3/16 of the cases, a dot-like positivity for EMA was detected. All tumors in our series were located in the supratentorial compartment. Median age of the patients at the time of diagnosis was 6.2 years. Median progression-free survival was 35 months (for 11 patients with data available). In summary, our findings suggest the existence of a novel group of supratentorial neuroepithelial tumors that are characterized by recurrent PLAGL1 fusions and enriched for pediatric patients.

Sievers P ，Henneken SC ，Blume C ，Sill M ，Schrimpf D ，Stichel D ，Okonechnikov K ，Reuss DE ，Benzel J ，Maaß KK ，Kool M ，Sturm D ，Zheng T ，Ghasemi DR ，Kohlhof-Meinecke P ，Cruz O ，Suñol M ，Lavarino C ，Ruf V ，Boldt HB ，Pagès M ，Pouget C ，Schweizer L ，Kranendonk MEG ，Akhtar N ，Bunkowski S ，Stadelmann C ，Schüller U ，Mueller WC ，Dohmen H ，Acker T ，Harter PN ，Mawrin C ，Beschorner R ，Brandner S ，Snuderl M ，Abdullaev Z ，Aldape K ，Gilbert MR ，Armstrong TS ，Ellison DW ，Capper D ，Ichimura K ，Reifenberger G ，Grundy RG ，Jabado N ，Krskova L ，Zapotocky M ，Vicha A ，Varlet P ，Wesseling P ，Rutkowski S ，Korshunov A ，Wick W ，Pfister SM ，Jones DTW ，von Deimling A ，Pajtler KW ，Sahm F ... -  《-》

Amplification of the PLAG-family genes-PLAGL1 and PLAGL2-is a key feature of the novel tumor type CNS embryonal tumor with PLAGL amplification.

Pediatric central nervous system (CNS) tumors represent the most common cause of cancer-related death in children aged 0-14 years. They differ from their adult counterparts, showing extensive clinical and molecular heterogeneity as well as a challenging histopathological spectrum that often impairs accurate diagnosis. Here, we use DNA methylation-based CNS tumor classification in combination with copy number, RNA-seq, and ChIP-seq analysis to characterize a newly identified CNS tumor type. In addition, we report histology, patient characteristics, and survival data in this tumor type. We describe a biologically distinct pediatric CNS tumor type (n = 31 cases) that is characterized by focal high-level amplification and resultant overexpression of either PLAGL1 or PLAGL2, and an absence of recurrent genetic alterations characteristic of other pediatric CNS tumor types. Both genes act as transcription factors for a regulatory subset of imprinted genes (IGs), components of the Wnt/β-Catenin pathway, and the potential drug targets RET and CYP2W1, which are also specifically overexpressed in this tumor type. A derived PLAGL-specific gene expression signature indicates dysregulation of imprinting control and differentiation/development. These tumors occurred throughout the neuroaxis including the cerebral hemispheres, cerebellum, and brainstem, and were predominantly composed of primitive embryonal-like cells lacking robust expression of markers of glial or neuronal differentiation (e.g., GFAP, OLIG2, and synaptophysin). Tumors with PLAGL1 amplification were typically diagnosed during adolescence (median age 10.5 years), whereas those with PLAGL2 amplification were diagnosed during early childhood (median age 2 years). The 10-year overall survival was 66% for PLAGL1-amplified tumors, 25% for PLAGL2-amplified tumors, 18% for male patients, and 82% for female patients. In summary, we describe a new type of biologically distinct CNS tumor characterized by PLAGL1/2 amplification that occurs predominantly in infants and toddlers (PLAGL2) or adolescents (PLAGL1) which we consider best classified as a CNS embryonal tumor and which is associated with intermediate survival. The cell of origin and optimal treatment strategies remain to be defined.

Keck MK ，Sill M ，Wittmann A ，Joshi P ，Stichel D ，Beck P ，Okonechnikow K ，Sievers P ，Wefers AK ，Roncaroli F ，Avula S ，McCabe MG ，Hayden JT ，Wesseling P ，Øra I ，Nistér M ，Kranendonk MEG ，Tops BBJ ，Zapotocky M ，Zamecnik J ，Vasiljevic A ，Fenouil T ，Meyronet D ，von Hoff K ，Schüller U ，Loiseau H ，Figarella-Branger D ，Kramm CM ，Sturm D ，Scheie D ，Rauramaa T ，Pesola J ，Gojo J ，Haberler C ，Brandner S ，Jacques T ，Sexton Oates A ，Saffery R ，Koscielniak E ，Baker SJ ，Yip S ，Snuderl M ，Ud Din N ，Samuel D ，Schramm K ，Blattner-Johnson M ，Selt F ，Ecker J ，Milde T ，von Deimling A ，Korshunov A ，Perry A ，Pfister SM ，Sahm F ，Solomon DA ，Jones DTW ... -  《-》

Central nervous system embryonal tumors with EWSR1-PLAGL1 rearrangements reclassified as INI-1 deficient tumors at relapse.

Central nervous system (CNS) embryonal tumors are a diverse group of malignant tumors typically affecting pediatric patients that recently have been better defined, and this paper describes evolution of a unique type of embryonal tumor at relapse. Two pediatric patients with CNS embryonal tumors with EWSR1-PLAGL1 rearrangements treated at Arkansas Children's Hospital with histopathologic and molecular data are described. These two patients at diagnosis were classified as CNS embryonal tumors with EWSR1-PLAGL1 rearrangements based on histologic appearance and molecular data. At relapse both patient's disease was reclassified as atypical teratoid rhabdoid tumor (ATRT) based on loss of INI-1, presence of SMARCB1 alterations, and methylation profiling results. CNS embryonal tumors with EWSR1-PLAGL1 rearrangements acquire or include a population of cells with SMARCB1 alterations that are the component that predominate at relapse, suggesting treatment aimed at this disease component at diagnosis should be considered.

Bielamowicz KJ ，Littrell MB ，Albert GW ，Parker LS ，Jayappa S ，Aldape K ，Gokden M ... -  《-》