Introduction: mucinous tumors of the appendix are a condition characterized by obstructive dilation of the cecal appendix caused by the intraluminal accumulation of mucous material. Their incidence is relatively low, accounting for approximately 0.2-0.3% of all appendectomies performed. Mucinous lesions are divided into two groups: 1. Non-neoplastic lesions (mucocele) 2. Neoplastic lesions (serrated polyps, hyperplastic polyps, low-grade mucinous appendiceal neoplasia, high-grade mucinous appendiceal neoplasia, mucinous adenocarcinoma). There is no typical clinical presentation for this pathology; however, it often presents as acute appendicitis or as a mass in the right lower quadrant. Improper management could lead to pseudomyxoma peritonei, which has a high mortality rate.Clinic case: a case of a patient diagnosed preoperatively with a large appendiceal mucocele is presented. An exploratory laparotomy, right hemicolectomy, and ileotransverse anastomosis were performed with a good postoperative recovery. The histopathological result reported a mucinous cystadenoma of the appendix.Conclusion: mucinous cystadenoma is an extremely rare pathology, and its perioperative identification is challenging due to its nonspecific clinical presentation. For this reason, tomography is recommended in the study of neoplasms of the right iliac fossa
