Leiomyosarcoma is a malignant tumor of smooth muscle cells and it usually originates from the uterus and the retroperitoneum. Leiomyosarcoma of the gastrointestinal tract is rare and leiomyosarcoma of the colon in even more rare, accounting for less than 0.1% of all colonic malignancies. It can be difficult to differentiate leiomyosarcoma from tumor of the retroperitoneum, especially if the mass invades both the colon and the retroperitoneum. We describe the imaging findings of a primary leiomyosarcoma of the descending colon which manifested as a palpable mass in the left lower quadrant of the abdomen and was diagnosed to be of colonic origin by identifying supply vessels of the mass on imaging studies, and the diagnosis was confirmed by surgicopathologic findings. Tel. 82-63-859-1920 Fax. 82-63-851-4749 E-mail: yjyh@wonkwang.ac.kr This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Index terms

No abstract