Risk analysis of submucosal invasive rectal carcinomas for lymph node metastasis to expand indication criteria for endoscopic resection.

In the 2010 guidelines for the treatment of colorectal cancer from the Japanese Society for Cancer of the Colon and Rectum (JSCCR), the criteria for identifying curable submucosal invasive colorectal carcinoma after endoscopic resection is as follows: differentiated adenocarcinoma, no vascular invasion, submucosal invasion depth <1000 μm and budding grade 1 (low grade). A total of 118 rectal submucosal carcinomas, treated by primary surgical resection or additional surgical resection with lymph node (LN) dissection, were analyzed. Relationships between clinicopathological findings and LN metastasis were evaluated. LN metastasis was found in 11.0% (13/118). There were no significant differences between clinicopathological findings and LN metastasis except for budding grade. Multivariate logistic regression analysis showed budding grade 2/3 (high grade) to be the independent risk factor for LN metastasis. When cases that met the curative condition of histological grade, tumor budding grade and vessel invasion together according to JSCCR 2010 criteria, the incidence of LN metastasis was only 2.2% (1/46, 95% confidence interval: 0.06-11.5%), regardless of the degree of submucosal invasion depth. In conclusion, even in cases of rectal carcinoma with submucosal deep invasion, the risk of LN metastasis is minimal under certain conditions.