Discussion

Placental chorangioma is the most common neoplasm of the placenta occurring in approximately 0.6% of all pregnancies [1]. In most cases, the tumor is less than 5cm in size and asymptomatic [2]. Chorangioma is considered a hamartoma or hyperplastic capillary lesion rather than a true neoplasm due to its inability to metastasize, and the tumor has no malignant potential [3]. Chorangiomas are usually found in the third trimester as a solitary nodule in the placental parenchyma. On gross examination, the chorangioma is well-circumscribed, without a fibrous capsule, and sharply demarcated from the surrounding placental parenchyma by a single or double layer of chorionic epithelium. It tends to have fleshy, congested, red to tan colored surface [4]. The most common location is in the fetal surface of the placenta, in proximity of the umbilical cord insertion. A larger tumor is usually attached to the chorion, which is a less perfused area. A few cases have been reported on the maternal surface, replacing the whole or some part of the placental lobe [4,5]. Chorangiomas tend to arise in areas of hypoperfusion. A hypoxic state is thought to lead to active proliferation of connective tissue and growth of villous capillaries mediated by vascular growth factors [6]. Pre-eclampsia, high-altitude, and fetal anemia have been associated with chorangioma, suggesting that decreased oxygen tension may play a role in the pathogenesis [7,8].

Chorangiomas greater than 5cm are referred to as a giant chorangioma and occur in approximately 1 in 2,700 pregnancies [2]. Giant chorangioma can be clinically significant, causing various fetomaternal complications. In a study reviewing 175 cases of chorangioma, approximately 34% of giant chorangiomas experienced complications [2]. Arteriovenous shunting in giant chorangioma can increase venous return to the fetal heart, causing hypervolemia, tachycardia, and cardiomegaly, leading to heart failure, hydrops fetalis, and fetal demise. Large lesions can also divert nutrients and oxygen from the fetus, manifesting as growth restriction. Placentomegaly occurs due to a hyperdynamic circulation as a result of arteriovenous shunting.  In such cases, fetus may suffer from anemia and thrombocytopenia due to sequestration of red blood cells and platelets by the tumor. Polyhydramnios can occur due to both direct transudation into the amniotic fluid and to fetal polyuria secondary to the hyperdynamic circulation. Additionally, preterm delivery and maternal mirror syndrome with generalized fluid overload and preeclampsia can occur with giant chorangiomas [2,8].

Prenatal diagnosis depends on ultrasound, however, chorangioma can cause an increase in maternal serum alpha-fetoprotein [3]. Ultrasound examination reveals a hypo- or hyperechoic, well-circumscribed mass, which is usually located underneath the chorionic plate near the umbilical cord insertion, and often protrudes into the amniotic cavity. Color Doppler demonstrates large vascular channels around and within the tumor [6,9]. In cases of giant chorangiomas, echocardiography should be performed to assess cardiac function and measure fetal middle cerebral artery peak systolic velocity for diagnosis of fetal anemia. Regular ultrasounds with Doppler studies are used to monitor tumor size, fetal growth, amniotic fluid volume, and signs of fetal anemia or heart failure. The frequency of exams is based on tumor size and associated complications. With small tumors, assessment may occur every 3-4 weeks, whereas in large tumors, the ultrasound scan may be done every 1-2 weeks [3]. These regular assessments can diagnose conditions that require intervention, such as polyhydramnios, hydrops, or hemolytic anemia.

Several interventions have been performed for pregnancies with complicated giant chorangioma and include endoscopic surgical devascularization, fetal transfusion for correcting anemia, chemosclerosis using absolute alcohol, and fetoscopic laser coagulation [3]. Therapeutic amniocentesis or maternal indomethacin therapy may be indicated for polyhydramnios. Early delivery may be recommended if there is evidence of poor growth, fetal hypoxia or hydrops. In pregnancies delivered preterm, steroid administration for fetal lung maturity acceleration can optimize postnatal outcomes [9].

Besides the histopathology examination, ultrasonography and particularly color Doppler sonography is helpful in differentiating chorangioma from other placental pathologies such as hematoma, infarcts, intervillous thrombosis, partial mole, leiomyoma, and placental teratoma. The pattern of blood flow to the tumor can assist in differentiating between different placental tumors [3,10].

Prognosis depends on the size of the tumor and associated maternal and fetal complications. Symptomatic giant chorioangiomas carry a higher risk of mortality at approximately 18% [2]. There is no increased risk of recurrence.

References

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