Five cases of complete HM, diploid with 2 paternal genome sets (CHM;PP), 5 cases of partial HM, triploid with 2 paternal and 1 maternal genome sets (PHM;PPM), and 5 cases of non-HM, with diploid biparental genomes (non-HM;PM) were stained with p57 Abs: 57P06, EP183, KP10, and KP39.
The findings confirm that trisomic pregnancies may demonstrate morphological villous features similar to hydatidiform mole, and that loss of p57(KIP2) expression occurs due to an absence of maternally transcribed genes on chromosome 11 and can therefore be independent of androgenetic complete hydatidiform mole.
A pilot Placental Molar Diagnostic (PMD) Service was established combining histopathology, p57 immunohistochemistry, and molecular genotyping analysis for both in-house and referred-in cases suspicious for HM or with a preliminary diagnosis of HM.
Negative p57(KIP2) expression was associated with the absence of embryonic tissues and excessive trophoblastic proliferation, which are features of androgenetic complete HMs and were associated with protein-truncating mutations.
The diagnosis of hydatidiform mole must be considered in perimenopausal women, and the combination of p57(kip2) immunostaining and HER2 fluorescent in situ hybridization seems to be a very useful testing strategy for difficult situations regarding the differential diagnosis of completed and partial hydatidiform mole.
Here, we describe a first trimester abortus with morphologic features consistent with a hydatidiform mole and p57 expression pattern supporting a diagnosis of PHM.
We recommend use of p57 immunohistochemistry and molecular genotyping to evaluate all products of conception specimens for which there is any consideration of a diagnosis of hydatidiform mole.
Concordant results were obtained in all cases, and p57(KIP2) immunostaining accurately identified all cases of CHM from the groups with a definitive or possible diagnosis of HM. p57(KIP2) immunohistochemistry is a time- and cost-effective means of distinguishing CHM from its mimics in challenging cases.
In all gestations p57KIP2 was strongly expressed in decidua and in intervillous trophoblast islands, which served as internal positive controls for p57KIP2 immunostaining. p57KIP2 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.