Discrimination of complete hydatidiform mole from its mimics by immunohistochemistry of the paternally imprinted gene product p57(KIP2)

The p57(KIP2) protein is a cell cycle inhibitor and tumor suppressor encode d by a strongly paternally imprinted gene. We explored the utility of p57(K IP2) as a diagnostic marker in hydatidiform. mole, a disease likely the res ult of abnormal dosage and consequent misexpression of imprinted genes. Usi ng a monoclonal antibody on paraffin-embedded, formalin-fixed tissue sectio ns, the authors evaluated p57(KIP2) expression in normal placenta and in 14 9 gestations including 59 complete hydatidiform moles, 39 PHMs, and 51 spon taneous losses with hydropic changes. p57(KIP2) was strongly expressed in c ytotrophoblast and villous mesenchyme in normal placenta, all cases of part ial hydatidiform moles (39 of 39) and all spontaneous losses with hydropic changes (51 of 51). In contrast, p57KIP2 expression in cytotrophoblast and villous mesenchyme was absent or markedly decreased in 58 of 59 complete hy datidiform moles. In all gestations p57(KIP2) was strongly expressed in dec idua and in intervillous trophoblast islands, which served as internal posi tive controls for p57(KIP2) immunostaining. p57(KIP2) immunohistochemistry can reliably identify most cases of complete hydatidiform mole irrespective of gestational age and is thus a useful diagnostic adjunct, complementary to ploidy analysis, in the diagnosis of hydatidiform mole.