Mucinous Cystic Adenoma of the Liver: A Thought-Provoking Case of an Uncommon Hepatic Neoplasm.

BACKGROUND Mucinous cystic neoplasm (MCN) of the liver is a rare hepatic neoplasm: a cystic, mucus-producing tumor. Histopathologic examination reveals ovarian-like stroma. The origin of MCN of the liver is still unknown, although ectopic ovarian-like stroma in the liver has been suggested as a possibility. We document a thought-provoking case of MCN of the liver, and intratumoral fatty tissue may support the opinion that ectopic ovarian-like stroma in the liver is a possible origin for both MCN and ovarian teratoma. CASE REPORT An expansive 10.5-cm cystic tumor was incidentally detected in a 71-year-old woman. Imaging studies revealed that the tumor was multiloculated, with cyst contents comprising mucus, muddy-looking fluid (inspissated bile), and hematoma. Imaging studies revealed fatty tissue and calcifications in the cyst walls. The diagnosis of MCN of the liver was made, although MCNs have never been reported to include fatty tissue. Extended left lobectomy was performed, and the tumor was curatively removed without any rupture. A multilocular cyst, mucus, calcifications, and fatty tissue were clearly observed on gross inspection. Histopathological examination revealed ovarian-like stroma. Evidence of malignancy was not detected. Her postoperative course was uneventful. To the best of our knowledge, our patient is the first case of MCN of the liver with intratumoral fatty tissue. This case may support the hypothesis that MCN originates from ectopic ovarian-like stroma in the liver. CONCLUSIONS We documented a thought-provoking case of MCN of the liver in detail, and this MCN accompanied with fatty tissue might originate from ectopic ovarian-like stroma.