IDH1 and brain neoplasm: As some of these uncommon morphologic features are shared with other brain tumors, they often represent diagnostic challenges: i) oligodendrogliomas, IDH-mutant, and 1p/19q codeleted often exhibit monomorphic rounded cells with pale cytoplasm and a “chicken-wire” vascular network; ii) ependymomas and angiocentric glioma characteristically show perivascular pseudorosettes; iii) glioneuronal tumors, in general, may exhibit extravascular positivity for CD34 and desmoplastic stroma (14).