A moderate size solid mass is seen within the placenta and bulging into the amniotic fluid.
Chorioangiomas or placental hemangiomas are the most common benign tumor of the placenta with an incidence at delivery of approximately 0.5-1% of placentas examined. The prevalence of large chorioangiomas is lower and varies from 1 in 8000 to 1 in 50,000 pregnancies. An excellent review of this subject particularly with respect to vascularity and complications was reported by Jauniaux et al. and also by Benirschke. Pathologically, chorioangiomas are hamartomas which arise as a malformation of the primitive angioblastic tissue of the placenta. There are two main histopathologic types of chorioangiomas: angiomatous, which are formed of numerous blood vessels and cellular, which consist of loose mesenchymal tissue, containing a few ill-formed vessels. Degenerative changes such as necrosis, calcification, hyalinization or myxoid changes are frequently present in large tumors. They represent an excessive proliferation of blood vessels in chorionic villi, thus they consist of small blood vessels that are embedded within the stroma of enlarged placental villi, which in turn are covered by trophoblastic epithelium. The angiomas are perfused by the fetal circulation and thus, when they are large, may represent a significant impediment to fetal cardiac activity. They may also sequester platlets, with resultant thrombocytopenia in the newborn. Interestingly enough, thrombosis in chorioangiomas may "cure" these tumors and cause existant hydrops fetalis to resolve.
Most chorioangiomas are small, single circular, encapsulated and intraplacental. They have only occasionally been observed during an ultrasound examination and are unlikely to be detected during gross pathologic examination, unless the placenta is sytematically sliced. Large chorioangiomas are of variable shape, divided by fibrous septa, and most commonly protrude from the fetal surface of the placenta near the cord insertion. These tumors are well circumscribed, have a different echogenicity from the rest of the placental tissue and have often been documented sonographically, particularly when they are associated with fetal complications.
Chorioangiomas are the most common placental tumors and are thought to be hamartomatous malformations. Chorioangiomas are associated with pre-eclampsia, intrauterine growth restriction, polyhydramnios, fetomaternal hemorrhage, fetal anemia, fetal thrombocytopenia and congestive heart failure of the fetus.
A recent study by Jauniaux and Ogle demonstrated that vascularization of the tumor is pivotal determinant factor in pregnancy outcome. When the tumor is avascular, no specific complications should be expected. When the tumor is vascularized, and in particular if it contains numerous large vessels, serial ultrasound and Doppler examinations are warranted to detect polyhydramnios and early features of fetal congestive heart failure.
As was mentioned above, numerous studies have reported that chorioangiomas are often associated with polyhydramnios and premature onset of labor and rarely with hydrops. It has been maintained that complications are only found in association with tumors measuring > 5 cm in diameter. This was not borne out in the study by Jauniaux et al where vascularization rather than size was more of a determinant in complications. The overrall incidence of polyhydramnios associated with a placental chorioangioma varies between 14 and 33%. Once again the development of polyhydramnios appears to be more related to vascularity rather than size. The etiology of increased fluid felt to be due to transudation through the walls of the abnormal vessels of the tumor and subsequently through the permeable fetal plate of the placenta.
The etiology of congestive heart failure in pregnancies with chorioangiomas is thought to be volume overload of the fetal heart via arterio-venous shunts in the tumor in addition to pooling of blood in the tumor which acts as a dead space, causing anemia and hypoxemia, aggravating the heart failure. Anemia may also be caused by fetomaternal hemorrhage and a microangiopathic hemolytic anemia due to entrapment and destruction of fetal erythrocytes in the vascular network of the chorioangioma. Several reports have documented elevated levels of maternal serum AFP in patients with chorioangiomas.
The differential diagnosis for chorioangiomas include: intraplacental abruption, venous lakes and intervillous thrombosis.
Jauniaux E, Ogle R. Color Doppler imaging in the diagnosis and management of chorioangiomas. Ultrasound Obstet Gynecol 15:463-467, 2000
Fox H. Pathology of Placenta. 2nd Edition. Philadelphia: W.B. Saunders, 1997
Jauniaux F, Kadri R, Donner C, Rodesch F Not all chorioangiomas are associated with elevated maternal serum alpha-fetoprotein. Prenat Diagn 11: 73-4, 1991
Spirt BA, Gordon L, Cohen WN, Yambao T. Antenaral diagnosis of chorioangioma of the placenta. Am ] Roentgenol 135: 1273-5, 1980
van-Wering JH, van-der Slikke JW. Prenatal diagnosis of chorioangioma associated with polyhydramnios using ultrasound. Fur] Obstet Gynecol Reprod Biol 1985; 19: 255-9, 1985
Eldar GT, Hochner CD, Arid I, Ron M, Yagel S. Fetal high output cardiac failure and acute hydramnios caused by large placental chorioangioma. Br] Obstet Gynecol 95: 1200-3, 1988
Jauniaux F, Campbell S. Sonographic assessment of placental abnormalities. Am] Obstet Gynecol 163: 1650-8, 1990
Chou MM, Ho ESC, Hwang SF Lee YH, Chan LI, Wen MC. Prenatal diagnosis of placental chorioangioma: contribution of color Doppler ultrasound. Ultrasound Obstet Gynecol 4, 332-4, 1994
Mucitelli DR, Charles EZ, Kraus FT. Chorioangiomas of intermediate size and intrauterine growth retardation. Pathol Res Pract 186: 455-8, 1990
Horigome H, Hamada H, Sohda S et al. Large placental chorioangiomas as a cause of cardiac failure in two fetuses. Fetal Diagn Ther 12:241-243, 1997
Haak MC, Oosterhof H, Mouw RJ. Pathophysiology and treatment of fetal anemia due to placental chorioangioma. Ultrasound Obstet Gynecol 14:68-70, 1999
Essen U, Orife S, Pollard K. Placental Chorioangioma: A case report and literature review. BJCP 51:181-2, 1997
Benirschke K. Recent trends in chorioangiomas, especially those of multiple and recurrent chorangiomas. Ped Develop Path 2:264-269, 1999