Transvaginal Colour Doppler in Trophoblastic Disease

Abstract

The trophoblastic cells forming the outer cell mass of the early blastocyst can be identified as early as 4–5 days after fertilization [8]. A few days later they start to penetrate the uterine mucosa, thus initiating the formation of the placenta. The trophoblastic cells erode the endothelial lining of the maternal vessels, making the exchange of nutrients possible. In addition to invasiveness, the trophoblasts of early pregnancy also display other tumour-like properties, such as explosive proliferation and evasion of immuno-surveillance [11]. The trophoblast does not invade beyond the endometrium and the mechanisms behind this strict control are not fully understood. However, there are data supporting the view that extraembryonic growth factors and receptor interactions are involved and controlled via local stimulatory loops [7]. In invasive mole and choriocarcinoma, the control mechanisms are no longer in effect. In invasive mole, placental tissue invades the myometrium and metastases can also develop. Since the villi cannot be distinguished microscopically from villi in hydatidiform mole, this is not a true cancer. Invasive mole can only occur following a molar pregnancy.