Bcl-2 expression as a novel immunohistochemical marker for ruptured tubal ectopic pregnancy

Programmed cell death by apoptosis occurs in fetal and maternal tissues during early pregnancy and plays an important role during implantation, decidualization, and in fetal development. In the regulation of apoptosis, bcl-2 is one of the central controlling genes, and acts by protecting the cell against apoptosis. It is postulated that invasiveness of ectopic trophoblast towards and through the muscularis zone of the tubal wall consequently leading to tubal rupture might be due to disturbed regulation of apoptosis. By means of immunohistochemistry and a computerized image analysis, bcl-2 immunostaining was localized and quantified in 36 randomly selected paraffin-embedded ectopic trophoblast tissue specimens collected from women undergoing surgery for ruptured (n = 18) and non-ruptured (n = 18) tubal ectopic pregnancies. Immunostaining was found in the villi syncytiotrophoblast in all patients, while the percentage of positive bcl-2 immunostained area (%PA) (P = 0.0009) and staining intensity (P = 0.0042) were consistently greater in the group of ruptured ectopic pregnancies. Including the variables %PA and saturation into a logistic regression model for a probability threshold of 0.5 (<0.5 = non-ruptured ectopic pregnancy, >0.5 = ruptured ectopic pregnancy) to identify tubal rupture, a sensitivity and specificity of 94.4% were found. It is suggested that elevated bcl-2 immunostaining in the syncytiotrophoblast layer reflects unlimited cell survival of ectopic trophoblast and could lead to the establishment of a circulating marker for tubal rupture.