Is It Possible to Judge the Submucosal Invasion of Colorectal Cancer by Conventional Colonoscopic Examination?

We previously reported differences in lymph node metastasis in submucosal invasive colon cancer depending on the depth of invasion. Consequently, the type of submucosal invasive colon cancer must be taken into consideration when selecting the therapeutic indication. A more detailed classification is therefore needed. We classified submucosal invasive colon cancer into two types on the basis of the degree of invasion and assessed the histopathology of specimens obtained by endoscopic or surgical resection to determine to which extent pathologic findings were detected with conventional endoscopic examination. We divided 68 cases of submucosal invasive colon cancer treated at our institution between 1995 and 2000 (endoscopic resection, 40 cases; surgical resection, 28 cases) into 2 groups with submucosal invasion of less than 1,500 μm and 1,500 μm or higher. Diagnostic accuracy was calculated for each type of gross configuration to determine the extent to which evaluation with conventional endoscopy is possible. Overall accuracy was 62, 87, and 96% in the pedunculated, subpedunculated and sessile, and superficial types, respectively, showing significantly poorer accuracy in the pedunculated and subpedunculated/sessile types (polypoid types) than in the superficial type. Specificity showed little difference with 100, 90, and 100%. Positive predictive value showed little difference with 100, 94, and 100% in the pedunculated, subpedunculated and sessile, and superficial types, respectively. Sencitivity was 29, 85, and 94%. Negative predictive value was 55, 75, and 88% in the pedunculated, subpedunculated and sessile, and superficial (IIa, IIa+IIc, IIc) types, respectively, with significantly poorer specificity in the polypoid types than in the superficial type. If conventional endoscopic examination reveals linearization on the tumor surface, the degree of submucosal invasion is almost certain to be 1,500 μm or higher. Overall accuracy and negative predictive value in particular were significantly poorer in the polypoid types than in the superficial type, but it was possible to differentiate submucosal invasion of less than 1,500 μm and 1,500 μm or higher with conventional endoscopic examination in 85% of cases