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What is Chorioangioma and explain in detail?
Chorioangioma, or chorangioma, is a benign tumor of placenta. It is a hamartoma-like growth in the placenta consisting of blood vessels, and is seen in approximately 0.5 to 1% pregnancies.  It is mostly diagnosed ultrasonically in the second trimester of pregnancy. Large chorioangiomas are known to cause complications in pregnancy, while the smaller ones are asymptomatic.

Presentation
Most chorangiomas are not clinically significant, i.e. they do not have an adverse effect on placental function.

Complications
Large (greater than 4 or 5 cm.) or multiple chorioangiomas may lead to complication. The complications are polyhydramnios, preterm labour, hemolytic anemia, fetal cardiomegaly, fetal thrombocytopenia, intrauterine growth retardation, preeclampsia, abruption of placenta and congenital anomalies.

Pathogenesis
The origin of chorioangioma is from primitive chorionic mesenchyme. It develops when the blood vessels and stroma undergo rapid proliferation independent of the surrounding tissue. Based on histological features, chorioangioma is classified by Marchetti into three types:
Cellular type : This type is immature and contains mostly cellular elements packed compactly.
Angiomatous (vascular) type : This is the most common type of choriocarcinoma. It is distinguished by the presence of numerous small blood vessels.
Degenerative type : This is the mature type with degenerative changes.Each type is believed to represent a phase of tumor development. Chorioangioma has no malignant potential.

Diagnosis
Most chorioangiomas are asymptomatic. They are generally picked up in second trimester scan. Chorioangioma is seen as a hypo- or hyperechoic circumscribed mass that is distinct from the placenta at gray-scale US examination. Large lesions may contain fibrous septa. It is seen protruding into the amniotic cavity near the insertion of the cord