The EP300:BCOR fusion extends the genetic alteration spectrum defining the new tumoral entity of "CNS tumors with BCOR internal tandem duplication"

Here we report two tumors with a HGNET-BCOR methylation class (MC) but harboring a BCOR fusion with the EP300 gene (encoding the protein p300 which is an acetyltransferase histone implicated in controlling cell growth and differentiation). SEE PDF] Interestingly, this same fusion was previously reported in gliomas [7] but these cases were distinct of our cases from radiology (infiltrative pattern), histopathology and immunohistochemistry (infiltrative proliferation with calcifications, composed of GFAP positive cells without expression of neuronal markers) [7]. [...]gliomas described by Torre et al. were in close vicinity to LGG with an MYB/MYBL1 alteration by t-Distributed Stochastic Neighbor Embedding plot (t-SNE) analysis whereas our cases were classified into the MC HGNET-BCOR and clearly clustered with HGNET-BCOR by t-SNE analysis (Fig. 4) [7]. [...]the EP300:BCOR fusion expands the spectrum of the alterations encountered in the MC HGNET-BCOR, and therefore, the terminology “CNS tumors with BCOR ITD” seems to be too restrictive. Because the BCOR immunohistochemistry does not allow detections of HGNET-BCOR with fusion, we recommand searching for alternative alterations of the BCOR gene in the event of radiological and histopathological suspicion of this diagnosis when ITD is absent.