Clinicopathologic Findings of Atypical Teratoid/Rhabdoid Tumor of the Central Nervous System

ABSTRACT

OBJECTIVE: Atypical teratoid/rhabdoid tumor(AT/RT) is a new entity among malignant pediatric brain tumors, and shows variable histopathologic features. The authors investigate the clinicopathologic and cytogenetic features of the tumor. METHODS: Five cases were included in this study ; three of them were primarily diagnosed, and two cases were reclassified from primitive neuroectodermal tumor/medulloblastoma to AT/RT. Mean age of patients at diagnosis was 5.6 years. The tumors were located in infratentorial or supratentorial areas. Maximum survival period was 13 months. RESULTS: Histopathologically, the tumors were mainly composed of modified rhabdoid cells and undifferentiated small cells, and mixed with epithelial, mesenchymal components, and other features mimicking glioma and chordoma. The histopathologic features were supported by polyphenotypic immunoreactivity, including epithelial membrane antigen, cytokeratin, vimentin, smooth muscle actin, and glial fibrillary acidic protein. Cytogenetic studies for karyotype analysis and fluorescent in situ hybridization revealed monosomy of chromosome 22 in two cases out of three cases of the tumor. CONCLUSION: Atypical teratoid/rhabdoid tumor may be an unique clinicopathologic entity, and histopathologic diagnosis should be made carefully by differentiating other polymorphous tumors of the brain.