Placental proteins in oncology.

Many placental proteins appear in the serum and tumours of patients with malignant disease, but few have achieved an established position in clinical management. Chorionic gonadotrophin is a sensitive and effective marker for trophoblastic disease. Gonadal germ cell tumours containing extraembryonic structures can secrete hCG and SPl, which both may provide unique clinical information about recurrent disease. Placental proteins belonging to the PP series are an interesting new group which has added to our knowledge of the biology of tumours. However, none of them has yet proven to be important in clinical practice. Placental alkaline phosphatase isoenzymes are secreted by seminomas and dysgerminomas, and, in some clinics, they are routinely examined for monitoring treatment of these tumours. Whereas the clinical usefulness of the above markers is well established for the monitoring of treatment and early detection of recurrent disease, none of them can be used for the screening of cancer in an apparently healthy population.