We present a case of a 9-year-old child with a malignant epithelioid neoplasm located in the retroperitoneum that was found to have a fusion of the ESWR1/CREM genes, confirmed through anatomopathological examination, immunohistochemical, and molecular biology studies. While similar cases have been reported in the literature for adult patients, they are very rare in children and appear to represent a new type of tumor. Our case emphasizes the importance of the correlation between pathological anatomy and genetics.