SEL1L and neoplasm: Here, we analysed the relationship of SEL1L with (1) tumour progression and cell proliferation, in association with TME; (2) stemness potential; (3) prognostic genetic and epigenetic markers (IDH1/2, TERT promoter and TP53 mutations, EGFR gene amplification, MGMT promoter hypermethylation, 1p/19q co‐deletion, ATRX status, LOH on 9p, 10q and 17p); and (4) patient survival and response to therapy.