Colonic gastrointestinal stromal tumor resulting in recurrent colic and hematochezia in a warmblood gelding.

A 14-year-old Trakehner gelding was evaluated for recurrent colic, with episodes occurring over 1 year. Signs were consistent with intermittent ascending colon obstruction and hematochezia. Necropsy examination revealed an ulcerated mass extending into the lumen of the right dorsal ascending colon. Gross and histologic appearance and immunoreactivity to c-kit (CD117), desmin, vimentin, and smooth muscle actin, were consistent with a diagnosis of gastrointestinal stromal tumor.