Simultaneous detection of imprinted gene expression (p57 ^KIP2) and molecular cytogenetics (FICTION) in the evaluation of molar pregnancies

OBJECTIVE: To simultaneously evaluate the p57 ^KIP2 antibody expression and genotype of individual cells from paraffin sections of molar pregnancies. STUDY DESIGN: Paraffin sections from 10 typical and unusual molar pregnancies were evaluated with the FICTION technique (Fluorescence Immunophenotyping and Interphase Cytogenetics as a Tool for the Investigation of Neoplasms), using immunofluorescence staining for the p57 ^KIP2 antibody and enumeration fluorescence in situ hybridization (FISH) probes. The unusual cases included androgenetic/ biparental chimeric complete hydatidiform moles (CHM) and mosaic partial hydatidiform moles (PHM). The unusual molar conceptions provided insight into interpreting atypical p57 ^KIP2 staining patterns and identifying androgenetic cells. RESULTS: The androgenetic/biparental chimeric CHMs demonstrated a negative p57 ^KIP2 staining pattern for the androgenetic cells and positive staining for the biparental cells. Concordantly, the FISH results showed delineation between the androgenetic cells and the biparental cells, indicating 2 distinct genotypes. Also, in the 2 cases of mosaic PHM, the partial loss of p57 ^KIP2 antibody staining was due to mosaic loss of chromosome 11, assumed to be the maternal copy. This provides a biological explanation as to how false interpretation could occur when evaluating p57 ^KIP2 immunostaining results. CONCLUSION: The FICTION technique is a valuable ancillary tool for simultaneously evaluating the genotype and p57 ^KIP2 expression in unusual molar pregnancies.