Abstract
The patient was a 75-year-old man. Colonoscopy revealed a 0-IIc+IIa lesion in the transverse colon. Because submucosal invasion was suspected, surgical resection was planned to remove this lesion. The second colonoscopic examination was performed on the day before the operation, and the lesion was found to have obviously diminished in size, indicating that the tumor regressed spontaneously. However, we were concerned that tumor cells remained, and thus, surgery was performed as scheduled. Histopathological examination of the resected tumor disclosed that small numbers of tumor cells remained. In conclusion, in a case with suspected spontaneous regression, treatment should be determined by keeping in mind the possibility of remaining cancer cells.
