OBSOLETE: Atypical teratoid/rhabdoid tumor

Atypical teratoid/rhabdoid tumor (AT/RT) is a highly aggressive and rare malignant tumor of the central nervous system (CNS) that predominantly affects very young children, most commonly those under three years of age. This Orphanet entry (251891) is marked as OBSOLETE, meaning it has been retired or reclassified within the Orphanet nomenclature, and information may now be catalogued under an updated or alternative entry. AT/RT is characterized by the presence of rhabdoid cells and typically arises in the brain (particularly the posterior fossa/cerebellum) or, less commonly, in the spinal cord. The tumor is strongly associated with biallelic inactivation or loss of the SMARCB1 (INI1/hSNF5) gene on chromosome 22q11.2, and rarely with SMARCA4 mutations. These genes encode components of the SWI/SNF chromatin-remodeling complex, and their loss drives uncontrolled cell growth. Clinical features depend on tumor location but commonly include increased intracranial pressure leading to headaches, vomiting, lethargy, and increasing head circumference in infants. Neurological deficits such as cranial nerve palsies, ataxia, and developmental regression may also be present. Because of its rapid growth, symptoms often progress quickly. AT/RT accounts for approximately 1–2% of all pediatric CNS tumors but represents a significant proportion of CNS tumors in children under one year of age. Treatment typically involves a multimodal approach including maximal safe surgical resection, intensive chemotherapy regimens, and in some cases radiation therapy, although the use of radiation is limited in very young children due to neurotoxicity concerns. Despite aggressive treatment, prognosis remains poor, with historically low survival rates, though recent intensified treatment protocols have improved outcomes for some patients. Ongoing clinical trials are exploring targeted therapies and novel agents aimed at the molecular pathways disrupted by SMARCB1 loss.

Common questions about OBSOLETE: Atypical teratoid/rhabdoid tumor