Atypical teratoid/rhabdoid tumor of the central nervous system: clinicopathologic and immunohistochemical features of four cases.

BACKGROUND: Atypical teratoid/rhabdoid tumor (AT/RT) is a rare aggressive infantile neoplasm of uncertain origin. This study was performed to assess the clinicopathologic and immunohistochemical features of four AT/RT cases. CASE REPORTS: Two cases were male and two were female, and their ages ranged from 8 to 103 months. Tumors were located in the cerebellum (two cases), frontoparietal lobe (one case), and third ventricle (one case). Histopathologically, the tumors were composed of rhabdoid cells and undifferentiated small cells mixed with epithelial or mesenchymal components. However, one of the tumors was composed predominantly of a mesenchymal component mimicking a sarcoma. Immunohistochemically, vimentin (4/4), epithelial membrane antigen (4/4), cytokeratin (3/4), smooth muscle actin (4/4), glial fibrillary acidic protein (4/4), S-100 (4/4), and synaptophysin (1/4) were positive in varying proportions, while desmin and INI-1 were negative in all the cases. All of the patients died within a mean of 14 months due to tumor progression despite the chemotherapy. Only one of our patients lived for 40 months after the diagnosis. In conclusion, AT/RTs are aggressive tumors. They can occur in a variety of locations, such as the third ventricle. Morphologically, a large spectrum can be seen, like predominantly sarcoma in appearance, but immunohistochemistry is helpful in the correct diagnosis.