Mucinous carcinoma is a tumor composed of gastrointestinal-type cells with intracytoplasmic mucin. They are unilateral solid-cystic masses. A 38-year-old G2 L2 woman with a complaint of rapidly increasing severe abdominal distension was referred. Surgery was performed and a huge complicated mass showed up. We sucked about 42 liters of brown color fluid out of the cyst and then we could extract the residual mass. Chemotherapy protocol began under the supervision of oncologic service. Despite diagnostic delay, before any dissemination the cystadenocarcinoma was removed. To our best knowledge, our patient had the biggest tumor among other previous case presentations.