[Neuroepithelial tumor with PATZ1 fusion - case report and focus on an ill-defined entity].

The neuroepithelial tumor with PATZ1 fusion is a recently described tumor type, at the border between central nervous system and mesenchymal tumors. The histopathological diagnosis of this neoplasm, not recognized by the 2021 WHO classification, is challenging due to its varied and non-specific morphologic features. Most cases are densely cellular with monomorphous nuclei. Perivascular pseudo-rosettes of the ependymal type and astroblastic features are frequent. Blood vessels may be hyalinized. The tumor may display low- or high-grade features. OLIG2 and GFAP are variably expressed. Guided by DNA methylation profiling, a pathologist aware of this tumor type will search for a fusion involving PATZ1 and EWSR1 or MN1. The physiopathology of neuroepithelial tumor with PATZ1 fusion is not fully understood. The prognosis appears to align with that of intermediate-grade tumors but follow-up data are scarce. The therapeutic management is often similar to that of high-grade neoplasms. Nonetheless, PATZ1 fusion is a potential therapeutic avenue that may lead to personalized and less aggressive treatments.