Due to the unusual diffuse glioma or sarcoma like-histological findings in mouse YAP1 fusion tumors, a larger cohort of human ST-EPN-YAP1 tumors will need to be investigated histologically and molecularly to determine the relevance of mouse YAP1 fusion driven tumors as a model for human ependymoma. The gene discussed is YAP1; the disease is sarcoma.