ABSTRACT
Malignant Rhabdoid tumor is a rare malignant neoplasm and is morphologically similar to rhabdomyosarcoma, but is different immunohistochemically. Most malignant rhabdoid tumors occur in the kidney of infants, and are rarely reported at extrarenal sites. Since Frierson and his collagues first described the malignant extrarenal rhabdoid tumor(MRT) in children in 1985, it has rarely been reported. The neoplasm is histologically and immunohistochemically identical to a renal malignant rhabdoid tumor. There have been no previous reports of this neoplasm in Korea. An MRT of the sacroiliac bone in a 11-year-old girl is described. Five months after the initial presentation, the patient is still alive with partial response to combination chemotherapy and radiotherapy. The authors review previous reports of extrarenal MRT, and discuss the pathologic characteristics, differential diagnosis, and treatment of this rare neoplasm.