Diagnostic and pathogenetic significance of increased stromal apoptosis and incomplete vasculogenesis in complete hydatidiform moles in very early pregnancy periods.

Hydropic swelling, trophoblastic proliferation, and stromal avascularity of chorionic villi are the key features of advanced cases of complete hydatidiform moles (CHMs). Recently, however, the use of high-resolution ultrasonography has enabled earlier detection of CHMs, and these show previously unrecognized histologic features such as numerous immature vascular networks, nonhydropic hypercellular stroma, and frequent karyorrhexis in the villous stroma. To determine whether stromal vasculogenesis is affected in CHMs of very early pregnancy period (VECM), we compared the number of mature and immature blood vessels and their precursors in the villous stroma and counted the rates of stromal apoptosis and proliferation, as defined by immunopositivity for cleaved caspase-3 and Ki-67, in 63 cases of VECM, 11 cases of partial hydatidiform mole (VEPM), and 10 samples of normal placental tissue (NP) before the 13th gestational week. Using antibody to CD31, we found that the number of mature blood vessels with distinct lumen was significantly reduced in both VECM and VEPM compared with NP (P<0.001), but the number of CD31-positive primitive stromal cells or immature vascular networks without lumen did not differ significantly among the three groups. Stromal apoptotic rate was significantly higher in VECM than in VEPM or NP (P<0.001), which was very useful in differential diagnosis. Our results suggest that complete vasculogenic differentiation is significantly retarded in VECM due to increased apoptosis in the precursor components of blood vessels. It may result in a lack of vascular drainage and cause progressive accumulation of vesicular fluid in the later gestational period.