A 55 -year-old woman presented at our hospital in 2017. In 2014, a large cyst had been detected in her liver by ultrasonography, and she was followed up at a clinic. Abdominal computed tomography(CT)revealed a large multilocular cystic tumor measuring 12 cm in diameter in the left lobe of the liver. Although no solid component was identified in the tumor, the cystic tumor was increasing in size, and the serum level of CA19-9 was elevated. Under a preoperative diagnosis of mucinous cystic neoplasm(MCN)of the liver, we performed extended left liver lobectomy. There were no postoperative complications. Histopathological examination of the resected specimen revealed low-grade intraepithelial neoplasia, and the epithelium covered an ovarian-type stroma. The ovarian-type stromal cells were immunoreactive for estrogen receptor and progesterone receptor. The definitive diagnosis of the tumor was MCN of the liver with low-grade intraepithelial neoplasia. Eight months after the surgery, the patient remains alive without any recurrence.