Site-specific Differences in Colonic Adenocarcinoma: KRAS Mutations and High Tumor Budding Are More Frequent in Cecal Adenocarcinoma

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Recent literature indicates that adenocarcinomas of the cecum differ with respect to molecular alterations compared with noncecal proximal colon adenocarcinomas and that cecal tumor site may be a prognostically relevant variable. We compared molecular alterations, histopathologic features, and disease-specific survival in a series of 328 colonic adenocarcinomas identified over a 2-year period and stratified by tumor location (cecum, right colon, and left colon). Overall, cecal adenocarcinomas demonstrated the highest frequency of molecular abnormalities with 74% harboring either a KRAS exon 2 or 3 mutation, a BRAF mutation, or DNA mismatch repair protein deficiency. KRAS mutations were more frequently seen in the cecum compared with all other tumor sites (P=0.03). KRAS mutations were identified in 46% of cecal adenocarcinomas compared with only 25% of adenocarcinomas of the right colon (P=0.004). Cecal adenocarcinomas more frequently displayed adverse histopathologic features, in particular high tumor budding (31%), compared with tumors of the right colon (18%; P=0.04) and tumors of the left colon (17%; P=0.02). Overall stage was the most important independent predictor of disease-specific survival in the multivariable analysis; however, cecal tumor site and high tumor budding were also predictive of poor survival, particularly in patients with stage III or IV tumors. In conclusion, cecal adenocarcinomas are characterized by a high frequency of KRAS mutations compared with noncecal right colon tumors, frequently display high tumor budding, and may be a prognostically relevant variable, particularly in patients with stage III or IV disease.

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