Placental protein 5 and pregnancy zone protein in ovarian cysts and benign cystic ovarian tumors

Placental protein 5 (PP 5), a serine protease inhibitor, was measured by radioimmunoassay in benign ovarian cyst fluids, especially in follicular and luteal fluids. PP 5 was detectable in 12 out of 29 cystic fluids; the levels ranging from greater than 1.0 to less than 100 micrograms/l. PP 5 was not detectable in the corresponding serum samples. Protein of the "pregnancy zone" (PZ) was found in 3 out of 11 follicular fluids (9-38 mg/l). Local production of PP 5 and PZ in cystic epithelia of the ovary was taken into consideration.