Atypical Teratoid/Rhabdoid Tumor: An Unusual Variant of a Rare Entity

Atypical teratoid/rhabdoid tumors (AT/RTs) of the central nervous system (CNS) are distinctive, malignant neoplasms of uncertain histogenesis. They are thought to be embryonal and are usually composed of varying amounts of rhabdoid-type cells, small primitive neuroepithelial cells, epithelial tissue and neoplastic mesenchyme. Diagnosis may be difficult due to this morphologic variability and usually depends on demonstrating the presence of a specific mutation on chromosome 22 (the hSNF5/INI1 gene) or by visualizing ultrastructural whorled masses of intracytoplasmic intermediate filaments. The prognosis is poor with the majority of patients dying within one year of diagnosis.We describe a case of an AT/RT in an 8 year old boy who died shortly after presentation and whose tumor at autopsy showed unusual gross and histologic features. Diagnosis was only made after electron microscopy and immunohistochemical stains revealed the characteristic features.