atypical teratoid rhabdoid tumor (Monarch Disease Ontology term MONDO_0020560) (ATRT) is a highly malignant central nervous system (CNS) rhabdoid tumor (RT) found almost exclusively in children. Also known as: AT/RT, ATRT, ATT/RHT, CNS rhabdoid neoplasm, CNS rhabdoid tumor, CNS rhabdoid tumour, atypical teratoid/rhabdoid tumor, atypical teratoid/rhabdoid tumor (WHO grade IV).