Collision tumor of the appendix: mucinous cystadenoma and carcinoid. A case report

Mucinous cystadenoma is the most common of benign neoplasms of the appendix and carcinoid is the most common type of primary malignant lesions of the appendix.We report a rare case of a 57-year-old female with combined mucinous cystadenoma and carcinoid tumor of the appendix.Dual carcinoid and epithelial neoplasia is a rare occurrence in the appendix.

A 57-year-old Caucasian woman presented after incidentally palpating a mass on her right iliac fossa. Imaging modalities revealed a cystic tumor in the right iliac fossa with a diameter of about 8 cm, originating either from the right ovary or the appendix. She underwent laparoscopic surgical exploration, which revealed appendiceal mucocele and appendicectomy was finally performed as well as excision of a right ovarian cyst. Pathological examination showed acollision tumor consisting of mucinous cystadenoma and carcinoid tumor of the appendix. Because of the size and extension of the carcinoid tumor, which the pathology report revealed, she underwent re-exploration and laparoscopic right colectomy.

Mucinous cystadenoma is rare, but it is the commonest of benign appendiceal tumours accounting for 0.6% of appendectomy specimens. It can present as appendicitis,mucocele or if the tumour ruptures, as pseudomyxomaperitonei. On the other hand, carcinoid is the most common type of primary malignant lesion of the appendix and 0.3-0.9%of appendectomy specimens, with small predominance in female patients. Rare cases of mucinous cystadenomas of the appendix coexisting with carcinoid tumors were reported before, but in our case it was a collision tumor with no transitional zone between them. Also, the clinical presentation of our patient and the differential diagnosis of ovarian lesions from appendiceal tumors is worth being mentioned.