Purpose This study's aim is to investigate the clinicopathologic characteristics of colorectal gastrointestinal stromal tumors (GISTs) and to evaluate the result of those tumors. Methods We retrospectively reviewed 22 patients who had been diagnosed with primary colorectal GISTs and who had undergone a surgical resection between October 1996 and July 2008. Results Colorectal GISTs accounted for 0.28% of all colorectal malignancies and 7.7% of all GISTs. Rectal GISTs (19, 86.4%) were more common than colonic GISTs (3, 13.6%). According to the National Institute of Health's (NIH) grading system, there were 1 (4.5%) very low, 5 (22.7%) low, 4 (18.2%) intermediate, and 12 (54.6%) high-risk tumors. The disease recurred in 7 patients (1 with intermediate risk and 6 with high risk). Recurrence sites were the liver (42.9%), the peritoneum (71.5%), and the lymph nodes (14.3%). Adjuvant imatinib therapy and/or radiation therapy were done for patients with microscopically positive margins of resection and high risk, of which one experienced a recurrence at 95 months after surgery. The five-year recurrence rates were 0% in the very-low-grade and low-grade groups, 33.3% in the intermediate-grade group, and 37.5% in the high-grade group. The five-year overall survival rates were 100% in the very-low-grade and low-grade groups, 66.7% in the intermediate-grade group, and 62.5% in the high-grade group. Conclusion Poor prognosis of colorectal GISTs was closely related to the tumor's histologic grade and size. Integrating surgery, molecular therapy, and radiation therapy might improve outcomes, but further study with more cases is needed.
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