EVALUATION OF KI-67 (MIB-1) IN PLACENTAS WITH HYDROPIC CHANGE AND PARTIAL AND COMPLETE HYDATIDIFORM MOLE

The separation of complete from partial hydatidiform mole and of parti al mole from placentas with hydropic change on gross and microscopic e valuation can be difficult, and ploidy provides important diagnostic i nformation. We applied an immunohistochemical marker of proliferation, Ki-67 (MIB-1), to 10 complete moles, 11 partial moles, and 8 placenta s with hydropic change to determine whether growth fraction differs in these three placentas and can aid in diagnosis. Ploidy was confirmed using flow cytometry and fluorescence in situ hybridization with probe s to chromosomes 7 and 2. The Ki-67-determined growth fractions (numbe r of positive cells/total number of cells) for villous stromal cells, cytotrophoblast, and proliferating trophoblast were evaluated separate ly by counting 200 cells of each population. Growth fraction on stroma did not differ among the three entities. Mean percent growth fraction for cytotrophoblast was 13.3% for hydropic change, 14.6% in partial m oles and 38.7% in complete moles (P = .004 hydropic change to complete moles, P = .003 partial moles to complete moles). There was no signif icant difference between hydropic change and partial mole. Mean percen t growth fraction for proliferating trophoblast was 38.5% in hydropic change, 25.9% in partial moles, and 67.1% in complete moles (P = .08 h ydropic change to complete moles, P = .004 partial moles to complete m oles). Again, no significant difference was identified between hydropi c change and partial moles. Ploidy analysis using fluorescence in situ hybridization and flow cytometry confirmed diploidy in hydropic chang e and complete moles and triploidy in partial moles. Ki-67 may be usef ul in separating complete moles from partial moles but not partial mol es from hydropic change.