To provide an integrated diagnosis, diffuse gliomas arecategorised according to their histological and molecularcharacteristics. TP53 mutation, IDH mutation, and 1p/19qco-deletion are examples of molecular diagnosticindicators. ATRX is a protein that remodels chromatin, andthe diffuse glioma classification algorithm may use itsmutation status as a molecular diagnostic marker. Anti-ATRX is utilised to detect mutant ATRX by comparing theexpression of ATRX in neoplastic cells to internal positivecontrols, such as neurones, glia, and endothelial cells.Grade II/III oligodendroglioma contains IDH mutant, ATRXwildtype, and 1p/19q co-deletion; p53 expression may alsobe used as a diagnostic tool. Grade II/III astrocytoma isclassified by IDH mutant, ATRX mutant, and 1p/19qretention. 1p/19q co-deletion and ATRX mutation areoften, but not always, mutually exclusive.