Hepatic endometriosis diagnosed by liquid-based cytology: a case report.

A 44-year-old woman presented to Emergency Department with sudden onset of severe upper abdominal pain. T2-weighted MRI image showed a large cystic mass with a thickened wall measuring 9.5 × 9.1 × 11.2 cm in the right hepatic lobe. It was radiologically interpreted as a cystic mass with differential diagnosis including echinococcal cyst, biliary cystadenoma, and malignant neoplasm. The cystic mass was intraoperatively aspirated and a liquid-based cytology preparation (ThinPrep) and a cell block were made. The ThinPrep slides showed three dimensional clusters of epithelioid cells with scant delicate cytoplasm and tissue fragments composed of small stromal cells with round to oval shaped nuclei and a small amount of dense cytoplasm lined by the cuboidal epithelial cells. Occasional ciliated cells and abundant hemosiderin laden macrophages were also present. The cell block showed many tissue fragments containing glands and stroma with associated hemorrhage and hemosiderin laden macrophages, typical of endometrial tissue. Although it is uncommon, hepatic endometriosis should be considered in the differential diagnosis of cystic liver mass in women, especially those with a history of endometriosis or obstetric/gynecologic surgery.