Nowadays, giant ovarian mucinous cystadenomas are a rare condition, due to early diagnose and treatment. We report the case of a 44-year-old patient, who was diagnosed and admitted in our department with a giant pelvi-abdominal mass. The patient was operated with very high-risk consent, thus an enormous ovarian cyst of approximately 30 kg was extirpated. Afterwards, an extensive histopathological analysis was performed in order to determine the exact clinicopathological entity of the giant tumor-enteric type of multilocular mucinous ovarian cyst adenoma with borderline areas, with benign proliferation. Although giant ovarian mucinous cyst adenoma with borderline areas is an extremely rare condition, when encountered it is a real challenge for both surgeon and pathologist.