P57KIP2 immunostaining is helpful in diagnosing

In pregnancies before 10 weeks, classic molar changes may not be apparent because villi may not be enlarged and molar stroma may not yet be edematous and avascularOne takes advantage of the differing ploidy to distinguish paial (triploid) moles from diploid entities. Another technique involves histological immunostaining to identify the p57KIP2 nuclear protein. Because the gene that expresses p57KIP2 is paternally imprinted, only maternally donated genes are expressed. Because complete moles contain only paternal genetic material, they cannot express this gene; do not produce p57KIP2; and thus, do not pick up this immunostain. In contrast, this nuclear protein is strongly expressed in paial moles and in non-molar pregnancies with hydropic change. As a result, the combined use of ploidy analysis and p57KIP2 immunostaining can be used to differentiate: (1) a complete mole (diploid/p57KIP2-negative), (2) a paial mole (triploid/p57KIP2-positive), and spontaneous aboion with hydropic placental degeneration (diploid/p57KIP2-positive).Reference: William's Obstetrics; 25th edition, chapter 20; Gestational trophoblastic diseases