Appendiceal intussusception caused by mucinous cystadenoma presenting as acute appendicitis

While appendiceal intussusception is an uncommon pathological condition, mucinous cystadenoma of the appendix is a particularly rare entity. We report a case of appendiceal intussusception induced by a mucinous cystadenoma presenting as acute appendicitis. A 37-year-old woman was admitted with a one-day history of acute onset, right lower abdominal pain. Computed tomography showed swelling of the appendix, a pathological mass in the ileocolic region and oedematous pericolonic fat stranding. Emergency laparotomy via a McBurney incision revealed that the base of the appendix was swollen and intussuscepting into the caecum. Palpation of the caecum demonstrated an intraluminal mass, 6cm in size, at the appendicocaecal junction. After extension of the McBurney incision, a caecotomy was performed to investigate the mass, following which a cauliflower-like tumour started to protrude. En bloc excision was undertaken of both the appendix and the tumorous mass with a clear surgical margin to send for frozen section analysis. The biopsy samples indicated a mucinous neoplasm. Ileocaecal resection was therefore performed with ileocolic anastomosis. The resected specimen contained a tumour arising from the appendix. The tumour measured 5.3cm x 5cm x 3cm in the caecal cavity and the appendix had invaginated into the caecum at its base. The cut surface of the appendix showed the mucinous tumour projecting into the caecal cavity. Microscopic examination revealed a low grade mucinous cystadenoma.