A Case of Appendiceal Cancer Wherein the Abdominal Abscess Ruptured into the Urinary Bladder Owing to Obstructive Appendicitis

: A 73-year-old woman presented to her doctor because of lower abdominal pain and distension. A neoplastic lesion in the lower abdomen was revealed, and she was referred to our department. Enhanced CT showed wall thickening in the urinary bladder and a 6 cm mass that extended to the appendix. An appendiceal tumor invading the urinary bladder or a urinary bladder tumor invading the appendix was suspected, and we planned surgical treatment. One month later, we repeated enhanced CT scanning on admission. The mass had shrunk, but the thickening of the urinary bladder wall remained, and an enhanced appendiceal tumor was visible. Surgery was performed and we found a 1 cm appendiceal tumor. Intraoperative pathological examination revealed appendiceal cancer. Therefore, we performed ileocecal resection, D2 lymph node dissection, and partial cystectomy. Final histopathological examination revealed appendiceal cancer with pT2N0M0, pStage Ⅰ. Taking into account the patient's clinical course, we diagnosed obstructive appendicitis with an abscess due to appendiceal cancer rupture into the urinary bladder.