Lymph Node Metastasis and Micrometastasis of Submucosal Invasive Colorectal Carcinoma: An Indicator of the Curative Potential of Endoscopic Treatment

This study investigated the correlation between clinicopathologic features of submucosal invasive colorectal carcinoma (sm-CRC) and its metastasis to the lymph nodes, including micrometastasis dectected by anti-human cytokeratin (CAM5.2) immunohistochemistry, in order to assess the curative potential of endoscopic mucosal resection (EMR) for sm-CRC. One hundred seventeen surgically resected sm-CRCs and their corresponding regional lymph nodes were examined. Eighteen of the 117 cases (15.4%) were positive for lymph node metastasis by H&E examination (overt metastasis), and micrometastasis was detected in 17 of the 99 (17.2%) remaining cases that were negative for overt metastasis. Lymphatic invasion and sprouting were risk factors for overt/micrometastasis, and micrometastasis, respectively, (p<0.0001/p=0.03,and p=0.01), and the minimum extent of cancer invasion in patients with lymph node metastasis (micrometastasis) was 850 μm in depth and 2500 μm in width. Tumors with a smaller extent of submucosal invasion than these values showed no lymphatic or venous invasion or sprouting. The present study indicates that sm-CRCs with an extent of submucosal invasion of less than 850 μm in depth and 2500 μm in width may not even have any risk of micrometastasis, and that EMR alone has complete curative potential in such cases.