Interstitial Cytotrophoblast Cells (ECL)

The interstitial cytotrophoblast cells migrate into the maternal dicidua and myometrium. The activity of these cells promotes the circumferential expansion of the placental site and recruitment of maternal arterioles, allowing subsequent expansion of the villous region of the placenta. Interstitial cytotrophoblast cells become multinucleated and more rounded as they move deeper into the maternal tissue, where they form cells called placental bed giant cells which are regarded as the terminally differentiated end-point of the extravillous pathway.