Ultrasound-histopathologic features of the utero-placental interface in placenta accreta spectrum

The objective of this study was to evaluate the relationship between utero-placental vascular changes on ultrasound imaging and histopathologic findings according to the grade of villous invasion in placenta accreta spectrum (PAS). The ultrasound features of 31 patients with singleton pregnancies diagnosed prenatally with low-lying/placenta previa accreta were compared with histopathology findings following caesarean hysterectomy (n = 25) or partial myometrial resection (n = 6). The number and degree of transformation of arteries within the superficial layer of myometrium were recorded. Cytokeratin 7 (CK7) immunohistochemistry was used to complement H&E analysis. All 31 patients presented with loss of clear zone, myometrial thinning and placenta lacunae. Subplacental hypervascularity and lacunae feeder vessels were found in 25 and nine cases, respectively. Large recent intervillous thromboses were found in one case with adherent villi and 12 cases with invasive villi, and showed a significantly different distribution according to lacunae scores. Thick basal plate fibrinoid deposits were found in all the areas of abnormally adherent and invasive villous tissue There was no significant difference in the mean count of partially remodeled vessels or vessels completely lacking remodeling according to the lacunae score and grade of placental invasiveness. EVT cells were arranged in superficial confluent sheets or superficial irregular clusters, or were scattered deep below the basal plate. Placental ultrasound and histopathologic features associated with PAS are more pronounced in invasive cases suggesting that they are secondary to the haemodynamic effects of abnormally deep placentation and transformation of the radial and arcuate arteries.