Risk factors for occult lymph node metastasis of colorectal cancer invading the submucosa and indications for endoscopic mucosal resection

PURPOSE: Although risk factors for histologically overt lymph node metastasis in patients with early-stage colorectal cancer have been clarified, the risk factors for occult lymph node metastasis are not clear. This study was designed to clarify risk factors for lymph node metastasis, including occult metastasis, in patients with colorectal cancer invading the submucosa and to determine the criteria for endoscopic resection of early colorectal cancer. METHODS: The risk factors for lymph node metastasis, including occult metastasis, were analyzed in 86 cases of surgically resected colorectal cancer invading the submucosa. The lymph nodes were assessed by immunohistochemistry with cytokeratin antibody CAM5.2. RESULTS: The frequencies of overt and occult metastasis to the lymph nodes were 13 percent (11/86) and 13 percent (10/75), respectively. Multivariate analysis showed vascular invasion (P=0.001) and tumor budding (P=0.003) to be independent risk factors for lymph node metastasis, including occult metastasis. For tumors with submucosal invasion < 1,000 mu m, no lymph node metastasis was found. The frequencies of lymph node metastasis for tumors with submucosal invasion of 1,000 to 2,000 mu m and >2,000 mu m were 21 and 37 percent, respectively. In considering combinations of risk factors, there was no lymph node metastasis in tumors having neither vascular invasion nor tumor budding and submucosal invasion of <= 3,000 mu m. CONCLUSIONS: Vascular invasion, tumor budding, and the degree of submucosal invasion were significant risk factors for lymph node metastasis, including occult metastasis. These three factors can be used in combination to identify patients requiring additional surgery after endoscopic resection.