Histopathological examination demonstrated a conventional leiomyoma with a focal area of malignant transformation to leiomyosarcoma, characterized by high cellularity, nuclear atypia, increased mitotic activity [5 per 2 high-power fields (HPF)], elevated Ki-67 index (40%), and loss of smooth muscle markers (SMA, desmin) in the malignant region. This evidence concerns the gene DES and leiomyosarcoma.