Immunohistochemical demonstration of placental protein 5 in trophoblastic tumours.

An immunoperoxidase technique was used for the detection of placental protein 5 (PP5) in tissue specimens from trophoblastic tumours. PP5 was detected in all of 15 cases of hydatidiform mole, in two out of six destructive moles and in one of seven choriocarcinomas. Though the biological importance of PP5 is not clear, its association with inactivation of plasmin suggests a role in the control of placental invasiveness.