A case of disseminated peritoneal metastases after 2-year conservative treatment for intramucosal colon carcinoma due to a perforation during endoscopic submucosal dissection.

A 70-year-old man was admitted to our hospital for the treatment of a large granular-type laterally spreading tumor in the splenic flexure of the descending colon. The preoperative diagnosis was intramucosal colon carcinoma and endoscopic submucosal dissection was performed. During treatment, a small perforation occurred accidentally. After conservative treatment with endoscopic suturing, the patient was discharged without additional surgery. The pathological diagnosis was an intramucosal carcinoma. One year after treatment, no local recurrence was observed on endoscopy, and abdominal computed tomography showed no obvious metastasis. Two years later, fluorodeoxyglucose-positron emission tomography/computed tomography, laparoscopic findings, and histopathologic findings by experimental excision of omentum revealed several disseminated peritoneal metastases from previously treated colon carcinoma. To the best of our knowledge, this is the first report of peritoneal dissemination after a small perforation during endoscopic submucosal dissection and conservative therapy for early-stage colon carcinoma. This report suggests the possibility of tumor dissemination in patients with small perforations during endoscopic procedures. Endoscopists should be aware of these rare potential risks and perform later surveillance carefully.