A 66-year-old man, who received surgical resection for advanced colorectal cancer of ascending colon 5 years ago, visited our hospital for surveillance colonoscopy. A colonoscopic examination revealed a IIa + IIc type lesion (10mm in diameter) in the sigmoid colon and a conventional image showed redness in the depressed area and fold convergence around the lesion. In narrow-band imaging (NBI) magnified images, a Japan NBI Expert Team (JNET) type 3 classification tumor was observed in the depressed area. A VI high-grade pit pattern was observed in magnified images after crystal-violet staining. We diagnosed the lesion as submucosal massively invasive cancer and surgical resection was performed with D2 lymph node dissection. Histological examination revealed well-to-moderately differentiated adenocarcinoma invading into the muscularis propria as well as a #241 lymph node metastasis. Although advanced colorectal cancers less than 10mm in diameter are relatively rare, we should mind possibility and importance of such a small lesion as shown in this case.
