Gastrointestinal stromal tumor of the rectum.

Gastrointestinal stromal tumors (GISTs) are characterized by remarkable variability in their differentiation potential, but most of these lesions do not display convincing smooth muscle or neuronal differentiation. The GISTs arising from the rectum or anal canal are extremely uncommon. We present a case of immunohistochemically proven GIST of the rectum, which was characterized by homogenous isointensity mass without necrosis or hemorrhage on T2-weighted image and by enhancement on gadolinium-enhanced study.