Whether presence or history of extracolonic primary malignancy is a risk for colorectal neoplasia is not fully known. In this study, 26,452 first-time colonoscopy cases were examined using a colonoscopy database. Among the analyzed subjects, 3,026 (11%) subjects had history or concomitance of extracolonic primary malignancy, while the remaining 23,426 subjects did not. Colorectal neoplasia was observed in 39% of all the subjects. A crude comparison showed that the prevalence of any type of colorectal neoplasia was higher in subjects with extracolonic malignancy than in those without (42% vs. 39%, p＝0.0012). However, after adjusting for confounding factors, the odds ratios (ORs) of subjects with extracolonic malignancy for having colorectal neoplasia, advanced neoplasia, and cancer were all less than 1.0, and all significantly different from those of subjects without extracolonic malignancy. Analysis according to the type of extracolonic malignancy revealed that gastric cancer cases had a significantly lower risk for colorectal advanced neoplasia (OR:0.81;95% CI:0.67-0.99). Among major malignancies, only esophageal squamous cell cancer cases had increased risk for colorectal neoplasia (OR:1.66;95% CI:1.20-2.29). Patients with presence or history of extracolonic malignancy did not carry a higher risk of occurrence of colorectal neoplasia
