A case of synchronous colorectal cancers including ascending and sigmoid colon cancer showing different genomic profiles in the examination of microsatellite instability, associated with acute appendicitis due to appendiceal goblet cell adenocarcinoma.

Background: Appendiceal goblet cell adenocarcinomas (GCA) are rare. Most patients who undergo appendectomy have acute appendicitis. The detection of synchronous colorectal cancer (SCRC) has increased with advances in diagnostic imaging and endoscopic examinations. However, only two cases of SCRC, including appendiceal GCA, have been reported to date. We recently encountered an extremely rare case of SCRC, involving appendiceal GCA, ascending colon cancer (ACC), and sigmoid colon cancer (SCC). Herein, we present this case and provide a discussion on the relevant literature.

Case presentation: A 69-year-old man presented to our hospital with right lower abdominal pain. Based on contrast-enhanced computed tomography (CE-CT), the patient was diagnosed with SCRC and acute appendicitis caused by appendiceal neoplasm and ACC. The patient underwent emergency laparotomy, and right colectomy with lymph node dissection (LD). Intraoperatively, we palpated the remaining segment of the colorectum whenever possible and incidentally detected SCC. Therefore, sigmoid resection with LD was suggested.

Conclusion: When treating acute appendicitis, it is important to consider the possibility of an extremely rare appendiceal tumor as the cause. If possible, CE-CT should be performed to ensure appropriate image interpretation during an unlikely SCRC event. J. Med. Invest. 72 : 194-201, February, 2025.