Synchronous mucinous cystadenoma of the appendix in a patient with colon cancer

Mucinous cystadenoma of the appendix is a rare condition. It is characterized by a cystic dilatation of the appendicular lumen with stasis of mucus inside it. There have also been reports of association with gastrointestinal tract, ovarian, and kidney tumors. In this report, an 82-year-old man was admitted to our hospital with several weeks’ history of low abdominal pain associated with anemia. Colonoscopy showed one tumor at 20 cm from the anal verge, and the entire colon was unobtainable due to bowel obstruction by the sigmoid colon tumor. Computed tomography indicated another cystic mass at the cecum. Following a sigmoid colon resection and appendectomy, the specimen was examined with histopathology, and a diagnosis of synchronous mucinous cystadenoma of the appendix and adenocarcinoma of the sigmoid colon was made. The patient recovered after surgery and was discharged from the hospital 12 days after the operation. We conclude that the incidence of synchronous mucinous cystadenoma of the appendix in colorectal cancer patients is low. Accurate preoperative diagnosis and careful surgical intervention can improve the prognosis of these patients.