22-year-old woman with gestational diabetes
Placental chorangiomas are caused by dysregulation of mesenchymal-endothelial cell interactions that determine vascular patterning within stem villi before birth. Pluripotential mesenchymal stem cells that are present in the paravascular region of stem villi are hypothesized to play a role in the development of chorangiomas. There is some role of reduced placental oxygenation in the pathogenesis. There is a risk of recurrence of this lesion in subsequent pregnancies.
Epidemiology and clinical presentation
Chorangiomas are the most common tumors of the placenta, occurring in approximately 1% of all pregnancies. They were first described in 1798 by John Clarke. Chorangiomas are benign tumors and could be classified as hamartomas. There are three morphological variants of chorangiomas: angiomatous, cellular, and degenerative.
The angiomatous variant is the most common type. It is associated with preeclampsia, pregnancy at high altitude, multiple gestation, and late preterm birth (32-37 weeks). Two related lesions are localized chorangiomatosis and diffuse multifocal chorangiomatosis. Localized chorangiomatosis is a villous process with similar histology as chorangioma but it permeates large stem villi dispersed between normal villi, instead of forming a single mass. In diffuse multifocal chorangiomatosis, there is excessive capillary growth with surrounding pericytes and collagen, involving secondary and tertiary villi.
Gross findings and diagnosis
Most chorangiomas are small and pose no risk to the mother or fetus. However, some chorangiomas that are large in size (more than 9 cm) can lead to arteriovenous shunting, polyhydramnios, hydrops fetalis, and fetal death. They may present as single or multiple well-circumscribed nodules. In the placenta, they are present either in the subchorionic or marginal regions, where there is lower oxygenation. The cut surface is firm and homogenous.