Immunohistochemistry and other ancillary techniques in the diagnosis of gestational trophoblastic diseases.

Gestational trophoblastic disease (GTD) encompasses entities ranging from ubiquitous hydatidiform moles to rare neoplastic gestational trophoblastic tumors. In practice, the histological diagnosis of GTD continues to have significant diagnostic inaccuracy with marked inter- and intra-observer variability, even among expert pathologists. Studies in correlation with genotypic evidence have confirmed a lack of accuracy in diagnosis of hydatidiform moles using histology alone. Applications of new immunohistochemical markers and molecular techniques have significantly enhanced the diagnostic precision of various GTDs in recent years. p57 Immunohistochemistry is a highly useful marker in confirming complete hydatidiform mole. PCR-based DNA genotyping has emerged as a powerful diagnostic measure to precisely classify both complete and partial hydatidiform moles. With acquisition of molecular diagnostic capabilities at most medical centers, these ancillary techniques have been increasingly integrated into the routine diagnostic workup of GTD. We propose an algorithmic approach combining histology and these ancillary tests to provide the best diagnostic practice possible. Under this algorithm, all cases with histological suspicion for complete mole are subject to p57 immunohistochemical confirmation, and all cases with histological suspicion for partial mole undergo DNA genotyping workup. Beyond hydatidiform mole, recognition of gestational trophoblastic tumors requires a high index of suspicion and application of immunohistochemical markers of trophoblast is helpful to accurately diagnose these rare tumors.