Malignant stromal tumor of the rectum (leiomyosarcoma): endosonographic and CT appearance with pathologic correlation

We report the CT and endorectal us features of a malignant stromal tu mor o f the rectum (leiomyosarcoma). On CT scan, rectal leiomyosarcoma appeared a s a large soft tissue mass, arising from the anterior rectal wall with exor ectal extension. On endorectal US, the rectal leiomyosarcoma presented as a well-defined hypoechogenic and heterogenous mass arising from the rectal m uscularis propria. The uncommon location of leiomyosarcoma to the rectum ma y simulate other rectal tumors such as adenocarcinoma on CT. As suggested b y this report, endorectal us demonstrated the muscular origin of the tumor.