Importance of histological evaluation in endoscopic resection of early colorectal cancer.

The diagnostic criteria for colonic intraepithelial tumors vary from country to country. While intramucosal adenocarcinoma is recognized in Japan, in Western countries adenocarcinoma is diagnosed only if the tumor invades to the submucosa and accesses the muscularis mucosae. However, endoscopic therapy, including endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD), is used worldwide to treat adenoma and early colorectal cancer. Precise histopathological evaluation is important for the curativeness of these therapies as inappropriate endoscopic therapy causes local recurrence of the tumor that may develop into fatal metastasis. Therefore, colorectal ESD and EMR are not indicated for cancers with massive submucosal invasion. However, diagnosis of cancer with massive submucosal invasion by endoscopy is limited, even when magnifying endoscopy for pit pattern and narrow band imaging and flexible spectral imaging color of enhancement are performed. Therefore, occasional cancers with massive submucosal invasion will be treated by ESD and EMR. Precise histopathological evaluation of these lesions should be performed in order to determine the necessity of additional therapy, including surgical resection.