Endometrial cyst of the liver

A 21-yr-old woman with a history of epigastric pain and a right upper quadrant mass was found to have a large parenchymal hepatic cyst on CT scan. The cyst was removed at surgery and found to be lined by ectopic endometrial tissue. This is, to our knowledge, the first recorded instance of endometriosis of the liver. The clinicopathological features of this patient and the possible pathogenesis of her most unusual hepatic lesion are discussed.