Mucinous tumors of uncertain malignant potential are rare; there are only occasional reports. We report the first case where the tumor was identified incidentally following resection of a perforated appendicitis. There was no previous history to suggest for a mucinous tumor. No other abnormalities were found at surgery. Treatment included right hemicolectomy, considering the risk of residual or metastatic disease of about 10%. The patient is alive and well twelve months after resection of the tumor.