Glioneuronal tumors PATZ1-fused: clinico-molecular and DNA methylation signatures for a variety of morphological and radiological profiles

Abstract

The neuroepithelial tumor, PATZ1-fused (NET-PATZ1), has been recently isolated as a distinct methylation class by DNA-methylation profiling and is characterized by recurrent PATZ1 fusions, in association with the EWSR1 or MN1 genes and a chromosome 22 chromothripsis. The clinical phenotype is mainly pediatric and features circumscribed supratentorial tumors. However, the histopathology is vastly heterogeneous (glial, glioneuronal, sarcomatous, multiphenotypic) and a cell of origin has not yet been identified, explaining the previsionary imprecise terminology of "NET". Moreover, extra-central nervous system (CNS) sarcomas also harboring the EWSR1::PATZ1 fusion have been reported and added to the current World Health Organization (WHO) Classification of Soft Tissue and Bone Tumors, in the chapter on undifferentiated small round cell sarcomas. However, their relationship to their CNS counterparts has not yet been studied. Herein, we analyzed a cohort of twelve CNS tumors with PATZ1 fusions in terms of clinical presentation, radiology, histopathology, immunohistochemistry, ultrastructure and DNA-methylation profiling and compared them to five extra-CNS sarcomas-PATZ1. Based on the reported GATA2 overexpression in NET-PATZ1, we also studied the potential interest of GATA2 immunoexpression as a diagnostic tool. We confirmed their distinct molecular characteristics and clinical phenotype but evidenced a morphological intratumoral heterogeneity with three recurrent morphological patterns (oligodendroglial-like, pleomorphic xanthoastrocytoma-like and spindle cells). Despite the unusual spindle and proliferative component in a CD34 + glioneuronal tumor (using electronic microscopy), these tumors present a favorable prognosis. Their histopathological features were all clearly distinct from their soft tissue counterparts. GATA2 immunostaining is highly specific for CNS tumors PATZ1-fused, but its sensitivity is perfectible and further studies are needed to confirm its use as a diagnostic tool. To conclude, our work highlights that CNS tumors, PATZ1-fused seem to represent a novel pediatric glioneuronal tumor type exhibiting a polymorphous morphology and provides new support for its addition as a provisional emerging pediatric circumscribed glioneuronal tumor type, low grade.

Keywords: DNA-methylation; EWSR1::PATZ1; Glioneuronal tumor; MN1::PATZ1.

Fig. 1

Imaging features of neuroepithelial tumors, PATZ1-fused. A-C Imaging of patient #1 on axial T2-weighted (A), post-contrast T1-weighted (B) and coronal FLAIR (C) images, showing a large heterogeneous right intraventricular mass with cystic content and contrast enhancement. D-H Imaging of patient #2 on axial T2-weighted (D), post-contrast T1-weighted (E), unenhanced CT (F), apparent diffusion coefficient map (G) and cerebral blood flow map (H) images, showing a right parietal mass with solid content, partial contrast enhancement, high density, diffusion restriction and low tumoral blood flow. I-J Imaging of patient #3 on coronal T2-weighted (I) and post-contrast T1-weighted (J) images, showing a left parietal cortical mass with a large cyst and a small enhancing nodule. K-M Imaging of patient #7 on axial T2-weighted (K), post-contrast T1-weighted (L) and cerebral blood flow map (M) images, showing a large heterogeneous right temporal mass involving the basal ganglia, with cystic content, contrast enhancement and low tumoral blood flow. N-P Imaging of patient #8 on axial post-contrast T1-weighted (N), apparent diffusion coefficient map (O) and sagittal unenhanced CT (P) images, showing a partially calcified mass, with low contrast enhancement and strong diffusion restriction that developed from the tectal region through the tentorial incisure

Fig. 2

Main morphological patterns of neuroepithelial tumors, PATZ1-fused. A-C A glial pattern composed of oligodendroglial-cells intermingled with a dense vascular network of hyalinized vessels (HPS, magnification x400). D-F A glial pattern composed of polymorphous and multinucleated cells with intranuclear inclusions (HPS, magnification x400). G-I A spindle cell pattern (HPS, magnification x400). J The adipocytic metaplasia (HPS, magnification x400). K-L A variable Ki67 labeling index (magnification x400). M Percentage of areas with the different morphological patterns: pattern 1 (the glial pattern composed of oligodendroglial-cells intermingled with a dense vascular network made of hyalinized vessels), pattern 2 (the glial pattern composed of polymorphous and multinucleated cells), and pattern 3 (the spindle cell component). Black scale bars represent 50 μm. HPS: Hematoxylin Phloxin Saffron

Fig. 3

Morphological, immunophenotypical and ultrastructural findings of glioneuronal differentiation in neuroepithelial tumors, PATZ1-fused. A Oligodendroglial cells and intranuclear inclusions (HPS, magnification x400, insert HPS, magnification x400). B-C Tumor cells with numerous eosinophilic granular bodies (HPS, magnification x400). D-E Variable expression of GFAP, moderate to diffuse (HPS, magnification x400). F-G Constant but variable expression of OLIG2 by tumor cells (magnification x400). H-J Constant extravascular immunopositivity for CD34 in a stellar and cellular manner (magnification x400). K Immunoexpression of synaptophysin by a subset of tumor cells (magnification x400). L Immunopositivity for chromogranin A in some tumor cells (magnification x400). M An astrocytic-like cell with intermediate filaments (asterisk) and dense core granules (neuronal cell) (arrowhead). N An oligodendroglial-like cell (arrowhead). O A neuronal cell with dense core granules (arrowhead). Black scale bars represent 50 μm. HPS: Hematoxylin Phloxin Saffron

Fig. 4

GATA2 immunoexpression illustrated in various tumor types. A-C Diffuse nuclear expression of GATA2 in neuroepithelial tumor-PATZ1. No expression in potential differential diagnoses (D supratentorial ependymoma, ZFTA-fused, E ganglioglioma, F pleomorphic xanthoastrocytoma, G infant-type hemispheric glioma, H desmoplastic infantile ganglioglioma, I meningioma, J intracranial mesenchymal tumor, FET::CREB-fused, K-L sarcomas-PATZ1). Black scale bars represent 50 μm

Fig. 5

DNA methylation-based t-distributed stochastic neighbor embedding distribution (A, and B focused on tumors with PATZ1 fusions). A Our tumors (NET-PATZ1: black spots and sarcomas-PATZ1: brown spots) were compared to reference samples from the Heidelberg cohort belonging to the DGONC (n = 15), DIG / DIA (n = 12), DLGNT_1 (n = 8), DLGNT_2 (n = 10), DNT (n = 40), EPN_MPE (n = 15), EPN-PFA (n = 91), EPN_PFB (n = 23), EPN_PF_SE (n = 12), EPN_SPINE (n = 21), EPN_SPINE_MYCN (n = 10), EPN_ST_SE (n = 12), EPN_YAP1 (n = 11), EPN_ZFTA (n = 70), EVNCYT (n = 15), GG (n = 22), HGNET_PATZ1 (n = 40), MYXGNT (n = 22), PGNT (n = 12), and RGNT (n = 14) methylation classes. The cases in this study were in close proximity to the HGNET_PATZ1 subgroup. In a more focused t-SNE analysis of the samples (B), NET-PATZ1 (black dots) were distinct from sarcomas-PATZ1 (orange dots)