Malignant rhabdoid tumor (MRT) is one of the most aggressive and lethal malignancies in pediatric oncology. Malignant rhabdoid tumor was initially described in 1978 as a rhabdomyosarcomatoid variant of a Wilms tumor because of its occurrence in the kidney and because of the resemblance of its cells to rhabdomyoblasts. The absence of muscular differentiation led Haas and colleagues to coin the term rhabdoid tumor of the kidney in 1981. Although renal malignant rhabdoid tumor was historically included in treatment protocols of the National Wilms Tumor Study (NWTS) Group, this tumor is now recognized as an entity separate from a Wilms tumor. In contrast to a Wilms tumor, a MRT of the kidney is characterized by the early onset of local and distant metastases and resistance to chemotherapy. Rhabdoid tumor (RT) is an aggressive pediatric soft tissue sarcoma that arises in the kidney, the liver, the peripheral nerves and all miscellaneous soft-parts throughout the body. RT involving the central nervous system (CNS) is called atypical teratoid rhabdoid tumor.