Mucinous Tumor of Uncertain Malignant Potential of the Appendix Mimicking Ovarian Cancer: A Case Report

Introduction: Mucinous tumor of uncertain malignant potential (UMP) of the appendix is an uncommon clinico-pathologic entity. It is a category used for dysplastic mucinous tumors that are difficult to classify as clearly benign or malignant. It appears clinically as a mass confined to the right lower quadrant or an adnexal mass, with or without pain. Case Report: We report the case of a 41-year-old woman admitted to our clinic with diagnosis of adnexal mass confined to the right lower quadrant, suggestive of ovarian tumor. Serum levels of the tumor markers CEA, CA-19.9, CA-15.3 were normal, except a slight increase of CA-125 level. The indication for surgery was the presence of a right adnexal mass observed at ultrasound examination. At laparotomy the appendix was twice the normal, filled with mucoid material (appendiceal mucocele) and the ovary was normal. Appendectomy and right oophorectomy were performed. Histologically, it was a mucinous tumor of uncertain malignant potential of the appendix associated with abundant mucoid material outside the appendix and inflammation of the neighboring organs, with accentuated reactive hyperplasia of mesothelium. Conclusion: Mucinous tumor of uncertain malignant potential of the appendix may mimick ovarian cancer; surgical exploration and histologic examination allow a correct diagnosis. Moreover, the clinical behavior of this lesion seems to depend on features of the neoplasm as a presence of mucine outside of the appendix.