Utility of chromosomal chromogenic in situ hybridization as an alternative to flow cytometry and cytogenetics in the diagnosis of early partial hydatidiform moles: a validation study.

OBJECTIVE The introduction of p57 immunohistochemistry has aided the distinction between early complete moles (CMs) and hydropic abortus (HA), but no single technique has emerged for the distinction between early partial moles (PMs) and HA. Flow cytometry and cytogenetics have been used, but these require specialized equipment/expertise. The goal of this study is validation of chromosome in situ hybridization (CrISH), focusing on comparing the results to those obtained by cytogenetic methods. STUDY DESIGN Archival paraffin blocks from molar and nonmolar gestations were retrieved. Sections were labeled with a chromosome 10 probe. Hybridization and visualization were performed using standard protocols. One hundred nuclei per sample were scored for the number ofsignals. RESULTS Of 50 hydatidiform moles, 22 were PMs and 28 were CMs. The CMs showed 2 signals in 25 cases and 4 signals in 3 cases. The PMs showed 3 signals in 21 cases and 2 signals in 1 case. For the HAs there were 2 signals in 24 cases, and 1 case had 3 signals. Concordance between CrISH and flow cytometry studies for molar gestations was 95%. CONCLUSION CrlSH is a highly effective adjunct in differentiating between PM and CM and between PM and HA. CrlSH is a simple, cost effective adjunct in evaluating molar gestations.