Abstract
A 66-year-old woman seen for lower abdominal pain and endometrial cytology findings of Class V was not found to have any abnormal findings in the uterus or ovaries in radiological examination, although she did have an appendiceal mucocele. The appendiceal tumor found in surgery was filled with mucin and multiple peritoneal nodules, diagnosed as mucinous cystadenocarcinoma of the appendix with peritoneal dissemination, so we operated right hemicolectomy, examined cytodiagnosis of cancer, and did open biopsy of the disseminated nodules. Histopathological examination showed differences in pathological structures between the appendiceal tumor and disseminated nodules, definitively diagnosed as synchronous mucinous cystadenocarcinoma of the appendix and primary peritoneal carcinoma. She underwent postoperative adjuvant chemotherapy for primary peritoneal carcinoma. This is, to the best of our knowledge, the first report of synchronous mucinous cystadenocarcinoma of the appendix and primary peritoneal carcinoma.
