Malignant rhabdoid tumor is a rare childhood tumor that commonly starts in the kidneys but also can occur in other soft tissues or in the brain, where it is referred to as atypical teratoid rhabdoid tumor (ATRT).Malignant rhabdoid tumor occurs most commonly in infants and toddlers; the average age of diagnosis is 15 months old. There are about 20 to 25 new cases of malignant rhabdoid tumor diagnosed each year in the United States. Cells from a malignant rhabdoid tumor can spread (metastasize) to other areas of the body. The treatment of malignant rhabdoid tumor involves a combination of therapies including surgery, radiation and chemotherapy. However, because this tumor is rare and aggressive, there is no defined standard of care, and treatment options may be tailored to your child's situation. Your child's doctor and other members of your care team will discuss the options with you in depth. Prompt medical attention and aggressive therapy are important for the best prognosis.