Very aggressive and malignant embryoma typically found in children and associated with high morbidity. Typically diagnosed after the first year of life; rarely found in adults. Arises in the kidneys or in extrarenal soft tissue. May involve the central nervous system, where it is referred to as atypical teratoid rhabdoid tumor. The condition is associated with chromosomal abnormalities that affect normal tumor suppression. Can metastasize.

Signs and symptoms include abdominal mass, neck mass, fever, irritability, peripheral nerve palsy, respiratory difficulties, and hypertension. Findings may be a result of tumor size and location.

Treatment includes tumor resection, aggressive chemotherapy, and radiotherapy if possible.