Benign hepatocellular tumor of the placenta.

Neoplasms of the placenta, other than trophoblastic tumors and chorangiomas, are exceedingly rare and predominantly include teratomas and metastatic maternal tumors. There has been a single case report of a hepatocellular adenoma-like neoplasm of the placenta that was characterized as most likely representing a specialized monodermal teratoma. We report a second apparent case of a hepatocellular adenoma-like lesion occurring in a preterm placenta with compelling morphologic, immunohistochemical, and ultrastructural validation of tissue hepatic in origin. It remains inconclusive that this lesion represents a neoplasm rather than a rare ectopic or heterotopic occurrence.