A 51-year-old female was referred to our hospital for examination of colorectal tumor. Conventional endoscopy revealed four aggregated colorectal lesions in the ascending colon, consisting of three 0-IIa+IIc lesions and one 0-IIa lesion with a white scar at the center of these lesions. As endoscopic complete resection of all lesions was thought to be difficult due to the central white scar, surgical resection was scheduled. However, in the endoscopic examination just before surgery, 90 days after the initial endoscopic examination at our hospital, three lesions had regressed spontaneously while one 0-IIa+IIc lesion remained with no morphological change. Endoscopic mucosal resection was performed for the residual lesion with complete resection, and histological examination revealed slightly invasive submucosal cancer with a depth of 260 μm without lymphovascular invasion. Spontaneous regression of colorectal cancer is extremely rare. We speculated the cause of spontaneous regression based on previous reports.
