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Gastrointestinal stromal tumor (GIST) is the designation for the specific c-kit–expressing and Kit signal–driven mesenchymal tumors. They account for approximately 0.1% to 3% of all gastrointestinal neoplasms and are the most common mesenchymal tumors that arise in the wall of the gastrointestinal tract.¹Most individuals are older than 50 years at the time of presentation and rarely younger than 40 years. Primary colonic GISTs are much less common than gastric (60%-70%), small intestinal (25%-35%), and anorectal (<5%) and most commonly involve the muscularis propria of the intestinal wall with propensity for exophytic growth.²Therefore, the most common presentation is that of a mass arising from the intestinal wall and projecting into the abdominal cavity. Gastrointestinal stromal tumors can be histologically identified as highly cellular spindle cell or epithelioid mesenchymal tumors, and morphology is somewhat site dependent. However, common to all these tumors is expression of Kit (CD117 antigen), which is a major diagnostic criterion.¹Although the prediction of malignancy in this tumor group is notoriously difficult, tumors that have mitotic activity counts exceeding 5 per 50 high-power field or those larger than 5 cm have a high frequency of intra-abdominal recurrence and liver metastasis, whereas those that fall short of these categories have uncertain malignant potential or intermediate risk for metastasis or recurrence.²The majority of colonic GISTs are malignant. Genetic markers, including Kitmutation status, which has been detected in at least 60% to 70% of cases, may be useful in more accurately identifying tumors with malignant potential.¹

The conventional therapy for patients with primary GISTs has been complete surgical resection.³Usually, only segmental resection of the underlying organ is required because GISTs tend to protrude from the tissue of origin and displace surrounding structures without invasion. Lymphadenectomy is not performed routinely in patients with GIST because lymph node metastases are rare. Meticulous surgical technique is necessary to avoid intraoperative tumor rupture, which is associated with a poor prognosis. Currently, there is widespread scientific and clinical interest in GIST because its principal pathogenetic defect has been identified and a specific molecular inhibitor of GIST (STI-571, imatinib mesylate) has been developed.⁴The exact role of STI-571 in primary GIST has not yet been established; in particular, high-risk patients with tumors larger than 10 cm could benefit from STI-571 as neoadjuvant and adjuvant treatment with conventional therapy.⁵

Correspondence:Alfredo A. santillan, MD, MPH, 4800 Alberta Ave, El Paso, TX 79905 (alfredo.santillan@ttuhsc.edu).

Accepted for Publication:November 1, 2005.

Author Contributions:Study concept and design: santillan, Agullo, and Landeros. Acquisition of data: santillan, Agullo, and Landeros. Drafting of the manuscript: santillan. Critical revision of the manuscript for important intellectual content: santillan, Agullo, and Landeros. Administrative, technical, and material support: santillan, Agullo, and Landeros. Study supervision: santillan, Agullo, and Landeros.