Membrane microscopic chorionic pseudocysts are associated with increased amount of placental extravillous...

To further study the pathogenesis of membrane microscopic chorionic pseudocysts (MCP), a presumptive placental chronic hypoxic lesion, this analysis retrospectively assessed the amount, maturity, proliferation, and apoptosis of membrane and chorionic disc extravillous trophoblasts in placentas with MCP.

Sections of 50 consecutive placentas with MCP (study group) and 50 placentas without MCP from pregnancies matched for gestational age (control group) were immunostained for human placental lactogen (hPL, a marker of trophoblastic maturity), M30 (a marker of irreversible apoptosis in epithelial cells), and E-cadherin and Ki-67 (double immunostaining, epithelial and proliferation markers, respectively). Positivity was evaluated quantitatively and analysed statistically.

A normal placenta features up to a seven cell thick membrane extravillous trophoblast layer and up to five cell islands or placental septa per chorionic disc section. Study group placentas featured 2.2 times more cell islands or placental septa (p < 0.01), and had membrane extravillous trophoblast layers 1.6 times thicker than control group placentas (p < 0.001). The degree of apoptosis, proliferation, and maturation in membrane and placental septa or cell island extravillous trophoblasts did not show statistically significant differences between the study group and the control group (p > 0.05).

The increased extravillous trophoblast accumulation and secretory activity is associated with MCP formation. The findings place MCP among other placental lesions associated with extravillous trophoblast accumulation and possibly dysfunction.