Myxoid glioneuronal tumor of the septum pellucidum and lateral ventricle is defined by a recurrent PDGFRA p.K385 mutation and DNT-like methylation profile

Excerpt

The septum pellucidum (“translucent wall”) is a thin, triangular membranous structure that runs sagittally from the corpus callosum down to the fornix and separates the left and right lateral ventricles of the brain. The septum pellucidum consists of two laminae of both white and gray matter. During fetal development, there is a space between the two laminae called the cavum septum pellucidum, which disappears during infancy in most individuals. The septum pellucidum is the anatomic site of origin of a spectrum of uncommon neuroepithelial tumors that include central neurocytoma, subependymoma, and low-grade glioneuronal tumors morphologically resembling either dysembryoplastic neuroepithelial tumor (DNT) or rosette-forming glioneuronal tumor (RGNT). Multiple case series or individual case reports have described DNT-like or RGNT-like low-grade glioneuronal tumors of the septum pellucidum and lateral ventricle, which are distinct from the typical cortical and fourth ventricular locations of DNT and RGNT, respectively [1, 5, 16]. Molecular analysis of these tumors has revealed the absence of IDH1/2 mutation and co-deletion of chromosomes 1p/19q that genetically define oligodendroglioma [5, 16]. Additionally, they have been found to lack alterations in FGFR1, BRAF, MYB, and MYBL1 that characterize the majority of DNT, RGNT, and other low-grade neuroepithelial tumors [5]. …