ATRX plays a role in chromatin regulation and maintenance of telomeres. It regulates incorporation of histone H3.3 into telomeric chromatin (1). ATRX is also a major component of various essential cellular pathways such as DNA replication and repair, chromatin higher-order structure regulation, gene transcriptional regulation, etc. (2) ATRX loss was observed in grades II/III astrocytomas, oligoastrocytomas, oligodendrogliomas, and glioblastomas. In grades II/III gliomas, most ATRX‐ loss cases had IDH1/2 mutations (3). ATRX mutations accompanied by an alternative lengthening of telomeres (ALT), impacted favorable survival of patients with astrocytic tumors (4). Assessment of ATRX loss by immunohistochemical staining captures the majority of mutations, indicating that the use of immunohistochemical testing in routine neuropathology diagnostics gives a reasonable sensitivity (5). ATRX mutation is also detected in neuroblastoma, osteosarcoma, and pancreatic neuro-endocrine tumors (6).