We aimed to evaluate the recurrence rate of colorectal neoplasia showing histologic lateral margin involvement after en bloc endoscopic submucosal dissection (ESD). We reviewed 527 colorectal lesions that were removed by en bloc ESD from 2005 to 2013 and followed by endoscopy. Based on the postprocedural pathologic reports, the lesions were categorized as follows: lesions with clear deep and positive lateral margins (n = 63) and lesions with R0 resection (n = 299). The tumor size was 45.7 ± 21.1 mm in the lateral margin-positive group and 30.6 ± 15.1 in the R0 group (P
