Primary Signet-ring Cell Carcinoma of the Vermiform Appendix Accompanied by Intra-abdominal Free Air Caused by a Perforation of the Vermiform Appendix

A 77-year-old woman visited our emergency outpatient department after experiencing abdominal pain for several days. Upon examination, she exhibited a board-like abdomen, and an abdominal computed tomography examination showed ascites and a small amount of free air on the surface of the liver. Although numerous diverticula were observed in the right colon, no apparent calcification or abscess formation was seen. We performed emergency surgery based on a diagnosis of panperitonitis associated with a perforation in a right colon diverticulum. The right colon was mobilized and carefully observed, and necrosis and perforation were seen at the tip of the appendix, located posterior to the cecum. Because no inflammation was observed at the base of the appendix, we performed an appendectomy. The presence of intra-abdominal free air arising from a perforation of the vermiform appendix is rare. Because postoperative histopathological examination revealed primary signet-ring cell carcinoma of the vermiform appendix and the resection margin was positive, we subsequently performed a right hemicolectomy using a two-stage procedure. Here, we report a case of primary signet-ring cell carcinoma of the vermiform appendix with perforation peritonitis. Although we were unable to diagnose the appendiceal cancer intraoperatively, this case illustrates the importance of considering the possibility of such cancer when choosing an operative method and of histopathologically examining resected appendices.