DES and leiomyosarcoma: The tumor is composed of highly atypical spindle cells with pleomorphic nuclei and mitotic activity on hematoxylin and eosin stains. The diagnosis is confirmed with immunohistochemistry staining positive for smooth muscle actin, vimentin, and desmin. Due to high recurrence rates, the prognosis for leiomyosarcomas remains poor and requires close follow-up to prevent progression.