Appendiceal cancer showing a submucosal tumor-like morphology in the ascending colon on colonoscopy: a case report.

Few reports have described a submucosal tumor (SMT)-like colon tumor together with appendiceal cancer. Moreover, some appendiceal tumors may exhibit a cecal protuberance. Here, we report an uncommon case of appendiceal cancer with an SMT-like tumor, which was a protuberant lesion in the ascending colon. To our knowledge, this is the first report in Japan. Our case was a 50-year-old man with an ascending colon tumor presented at our hospital for further evaluation of this lesion. This was discovered as a cystic lesion near the ascending colon on colonoscopy. Our initial diagnosis was an ascending colon SMT-like tumor, and our treatment strategy was laparoscopic resection. The differential diagnosis was appendiceal cancer or mucocele. Postoperative pathological findings led to a diagnosis of adenocarcinoma of the appendix. The postoperative course was uneventful, and the patient was followed up with computed tomography and blood sampling on an outpatient basis.