Abstract
A pelvic tumor was detected as an incidental finding of computed tomography (CT) in an asymptomatic 76-year-old man. CT and magnetic resonance imaging examinations revealed extension of the 10×6×5cm tumor from the pelvis to the perineum. The tumor was multinodular in shape and exhibited exoluminal growth from the rectum. No invasion by the tumor or enlarged lymph nodes were detected. These findings suggested a submucosal tumor, probably a gastrointestinal stromal tumor that arose from the rectal wall. The tumor was removed by a trans-sacral approach. It appeared milky white, multinodular in shape, and elastic soft, and it was attached to the wall of the rectum by a stalk. Histological examination revealed spindle- or pleomorphictumor cells containing disproportionate nuclei. Immunohistochemical examination revealed that the tumor cells expressed CD34, desmin, SMA, and vimentin, but not KIT and S-100. We therefore diagnosed the tumor as a c-kit-negative gastrointestinal stromal tumor of the rectum.
