Grossly apparent and microscopically intermediate trophoblast-lined subchorionic, septal, and cell island cysts are relatively common placental findings. To analyze the clinicopathologic correlations of histologically similar but grossly inapparent microscopic chorionic pseudocysts (lakes) arising in the chorion laeve of placental membranes (mccpm), selected placental and clinical parameters of all 172 consecutive placentas with mccpm (study group, sg) and all consecutive 3743 placentas without mccpm (comparative group, cg) from years 1994 through 2005 were statistically compared; mccpm were observed in 4.3% of all placentas and in 14.9% of placentas from preeclamptic mothers from 24- to 42-week pregnancies, their gestational weeks' distribution almost mirroring that of the distribution of preeclampsia, with a peak in the middle of the 3rd trimester. Microscopic chorionic pseudocysts (lakes) arising in the chorion laeve of placental membranes were statistically significantly more common in patients with preeclampsia and maternal diabetes mellitus. In placentas with mccpm, decidual arteriolopathy, homogeneous placental maturation, global hypoxic pattern of placental injury, chorangiosis, placental infarction, laminar necrosis of membranes, stem obliterative endarteritis, erythroblasts of fetal blood, and decidual hemosiderosis were statistically significantly more common, while acute chorioamnionitis, villous fibrosis, and villous edema were less common (P < or = 0.05). There were no statistically significant differences between sg and cg in meconium staining, retroplacental hematoma, perivillous fibrin deposition, intervillous thrombi, chronic villitis, chorangiomas, placenta accreta, amnion nodosum, and marginate/vallate placenta. Highly statistically significant associations of mccpm with preeclampsia and a cluster of placental lesions known to be linked to placental hypoxia indicate that the mccpm form in response to hypoxia, particularly in patients with preeclampsia; mccpm should therefore be regarded and reported as a hypoxia-associated placental lesion.
