Perinatal/Neonatal Casebook ⅢⅢⅢⅢⅢⅢⅢⅢⅢⅢⅢⅢⅢⅢ Placental Pathology Casebook

Kurt Benirschke, MD, Section Editor 81,000 on day 4 and subsequently to 172,000 and then 450,000. Mac- Contributed by Peilin Zhang, MD roscopic examination of the fetal surface of this 440-gm placenta Kurt Benirschke, MD (Figure 1A) showed a remarkably yellowish opacification and identified markedly enlarged, tortuous fetal blood vessels (arteries and Two cases of placental surface vessel aneurysms are presented. One case veins). The maternal surface was partially infarcted (approximately was associated with severe fetal intrauterine growth restriction and fetal one-half of the total placental volume) and somewhat resembled that thrombocytopenia. The other case was associated with “molar of “maternal floor infarction,” except that it was localized (Figure transformation” of placental villous tissue. 1B). Microscopic examination showed multiple infarcted areas in Journal of Perinatology 2000; 1:63–65. placental tissue and hemosiderin deposits in the membranes. There were many mural thrombi in the massively enlarged surface varicosi- ties that extended into the main stem villi. No features of maternal floor infarction syndrome were present. The placental surface blood vessels show a remarkable structural diversity and differences in size. Bhargava and Raja1 have studied Case 2 this complexity and referred to a relative frequency of vascular This placenta was from the pregnancy of an 18-year-old woman with tortuosity, pleading for a more systematic study of these vessels. a 35 week intrauterine pregnancy. A 2297-gm girl was vaginally deliv- The frequency of abnormalities in the vascular structure of chori- ered without complication. Gross examination revealed that a large onic vessels has also often been related to other placental anoma- and separate portion of this enlarged placenta had the appearance of lies, such as the absence of one umbilical artery, and to cord inser- molar transformation, and there was aneurysmal distension of the tional abnormalities. Aneurysms, however, are uncommon. Those fetal surface vessels. Previous amniocentesis and cytogenetic studies of the umbilical cord are especially infrequent findings during had shown a normal 46,XX karyotype, and the neonate with this routine placental examination, and they may or may not be asso- placenta developed normally. One-third of this 858-gm placenta was ciated with fetal consequences, largely depending on their size and replaced by what would usually be called a “partial hydatidiform secondary pathological changes.2,3 Aneurysms of the placental mole” (Figure 2A). Initially, we interpreted this placenta as presum- surface vessels, however, occur more commonly and are composed ably from a set of fraternal twins, one 46,XX and normal, the other of different types. Such vascular lesions recently have also been presumably triploid. Flow cytometry study, however, ascertained that identified prenatally by ultrasonography.4 Complications of sur- both sides of the placenta were found to be uniformly diploid (data face vessel aneurysms include rupture, hemorrhage, and, most not shown). Because of the extensive vascularization of the hydropic importantly, thrombosis. Here we report two cases of serpentine vesicles, with perfusion from the normal fetus (Figure 2B), this vascu- (occasionally also referred to as cirsoid) aneurysms of the placen- larization of hydropic villi interpreted as not representing a “complete tal surface vessels. One of the cases is associated with vascular hydatidiform mole.” thrombosis and consumptive fetal thrombocytopenia, whereas the other is associated with placental cystic “molar transformation.” DENOUEMENT AND DISCUSSION Case 1 Serpentine Aneurysms of the Placenta With This 37-week pregnancy of a 32-year-old gravida 3, para 2 woman Fetal Consequences resulted in a severe, symmetrically growth-restricted neonate The primary cause of surface vascular aneurysms of the placenta is weighing 1300 gm who was delivered by cesarean section because unknown. They may represent true congenital anomalies, as sug- of “fetal distress.” Apgar scores were 5 and 7 at 1 and 5 minutes, gested by Lemtis.5 He inferred this because the aneurysms described by respectively. The neonate did well in the intensive care unit. His this author were usually associated with atypical insertion of the um- initial platelet count was 44,000, and this count slowly climbed to bilical cord, a single umbilical artery, fetal growth retardation, and other placental anomalies. Aneurysms have been either arterial or Department of Pathology, University of California, San Diego Medical Center, San Diego, CA. venous malformations, but arteriovenous malformations have not Address correspondence and reprint requests to Kurt Benirschke, MD, Department of Pathol- ogy, University of California, San Diego Medical Center, 200 West Arbor Drive, San Diego, CA been described (excepting the poorly-documented case by Richards et 6 92103-8321. al. ; therefore, aneurysms have not been considered to behave as

cause of the neonatal thrombocytopenia. The many large areas of placental infarction observed were due to thrombosis and malperfu- sion of the placental tissue by the fetal rather than maternal vessels. Neonatal thrombocytopenia and transient thrombocytopenic purpura associated with placental thrombosis have been described to occur in three neonates by Williams and Benirschke,12 a complication that was associated with other cases of prenatal placental thrombosis. Indeed, disseminated intravascular coagulation of the fetus has been diag- nosed prenatally by Richards et al.6 in the presence of a large aneurysm of the umbilical cord. Although they suggested that it repre- Figure 1. A: Placenta of case 1 with an opaque, yellowish fetal surface and mas- sented an arteriovenous shunt, they supplied no confirmatory data. sively enlarged aneurysmal chorionic blood vessels. B: Maternal surface of case 1 showing a large area of yellowish infarction that simulated maternal floor infarct. That fetal vascular thrombosis can lead to a type of placental infarction has been described by Fox13 and further illustrated by Kraus.14 McDermott and Gillan15 also showed in their study of the mechanism “arteriovenous shunts.” True aneurysms are very uncommon patho- of infarction that reduced fetal blood flow may lead to placental in- logic features of the placenta and may be difficult to separate from farction. The histopathology of such infarcts, however, differs substan- pure tortuosity of vessels. Lemtis5,7 presented the most extensive study tially from the more common variety that is caused by obstruction of of placental aneurysms, finding them as often as in 2.5% of placentas, maternal blood flow to the intervillous space. It results primarily in a much more commonly than the 0.81% found by Wentworth.7,8 Lemtis condensation of villous stroma with absent capillaries but persistence reported on placental aneurysms in general and referred to the type of trophoblast. described here as “serpentine,” representing the least frequent type (7.3% of his 25 cases). Smaller, single, navicular, and saccular aneu- The unusual finding of our second case is that thrombosis of the surface vessel aneurysms resulted in molar villous transformation of a rysms were found to be much more frequent, and they have also been 5 previously discussed by us.9 Lemtis found that more than one-third of portion of the placenta. A similar finding was made by Lemtis, who neonates were growth-restricted, and one of the placentas described by described a case with molar transformation secondary to an aneu- 16 him also had a molar configuration, not unlike our second case. rysm. Sander described five similar placentas, referring to this Similarly, Lee et al10 described a huge placenta (1490 gm) with a pathologic finding as “pseudomolar” change. We hypothesize that the typical cirsoid angiomatous configuration that arose from the umbili- molar hydropic degeneration occurred because trophoblastic water cal vein of an otherwise normal umbilical cord. The cord of that transfer was continuing while fetal venous return was impeded, thus growth-restricted neonate had a membranous insertion. The infant leading to water stagnation in the villi. When thrombosis becomes was anemic but did well after transfusion. Kristiansen and Nielsen11 complete, villous infarction takes place. had three somewhat similar cases of dilated fetal placental surface blood vessels with thromboses as causes of death. Their cases, how- Acknowledgments ever, may not truly deserve the term “aneurysm;” rather, they were Case 2 was kindly referred to us by Dr. C. D. Clark, Providence Alaska Medical Center, mainly vascular ectasias. Anchorage, AK. Our first case showed thrombosis of the aneurysmal fetal surface vessels and infarction of a portion of the placental tissue. We believe References that the consumption of platelets by this thrombosis was the principal 1. Bhargava I, Raja PTK. An anatomical study of the foetal blood vessels on the chorial surface of the human placenta. II. In abnormalities of development. Acta Anat 1970;76:299–312. 2. Fortune DW, O¨ sto¨r AG. Umbilical artery aneurysm. Am J Obstet Gynecol 1978; 131:339–40. 3. Heifetz SA, Ruedra-Pedraza ME. Hemangiomas of the umbilical cord. Pediatr Pathol 1983;1:385–98. 4. Reinhart RD, Wells WA, Harris RD. Focal aneurysmal dilatation of subchorionic vessels simulating chorangioma. Ultrasound Obstet Gynecol 1999;13:147–9. 5. Lemtis H. U¨ ber Aneurysmen im fetalen Gefa¨ßapparat der menschlichen Pla- zenta. Arch Gyna¨kol 1968;206:330–47. Figure 2. A: Portion of the placenta of case 2 with marked molar transforma- 6. Richards DS, Lufti E, Mullins D, Sandler DL, Raynor BD. Prenatal diagnosis of tion of villous tissue. B: Histologic appearance of villi from the “molar” portion of the placenta from case 2. Note the large number of fetal capillaries and their fetal disseminated intravascular coagulation associated with umbilical cord blood content. arteriovenous malformation. Obstet Gynecol 1995;85:860–2.

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7. Lemtis H. Die Sto¨rung der feto-placentaren Blutzirkulation und ihre Bedeutung. 12. Williams JH, Benirschke K. Chorionic vessel thrombosis: a possible etiology of Arch Gyna¨kol 1969;207:59–60. neonatal purpura. J Reprod Med 1978;20:285–8. 8. Wentworth P. Some anomalies of the foetal vessels of the human placenta. J Anat 13. Fox H. Thrombosis of foetal arteries in the human placenta. J Obstet Gynaecol Br 1965;99:273–82. Commonw 1966;73:961–5. 9. Benirschke K, Kaufmann P. The Pathology of the Human Placenta. New York: 14. Kraus FT. Placenta: thrombosis of fetal stem vessels with fetal thrombotic vascu- Springer-Verlag; 1994. lopathy and chronic villitis. Pediatr Pathol Lab Med 1995;16:143–8. 10. Lee GK, Chi JG, Cha KS. An unusual venous anomaly of the placenta. Am J Clin 15. McDermott M, Gillan JE. Chronic reduction in fetal blood flow is associated with Pathol 1991;95:48–51. placental infarction. Placenta 1995;16:165–70. 11. Kristiansen FV, Nielsen VT. Intra-uterine fetal death and thrombosis of the um- 16. Sander CM. Angiomatous malformation of placental chorionic stem vessels and bilical vessels. Acta Obstet Gynecol Scand 1985;64:331–4. pseudomolar placentas: report of five cases. Pediatr Pathol 1993;13:621–33.

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