Cairo, Egypt

Synonyms: Cytotrophoblastic cysts.

Definition: Placental cysts are sonolucent areas that can be detected antenatally by ultrasound; they have a round or oval cavity, usually isolated from the placental circulation and contain a gelatinous fluid. These cysts are located within the placental tissue (septal cysts), or under the fetal plate (subchorionic cyst)³.

Prevalence: Placental cysts are found in 20% of placentae examined at term³.

Etiology: Unknown

Differential diagnosis: Placental tumors such as chorioangioma, (hyperechoic, on ultrasound examination), and rarely, early vanishing twin (there would be an embryo inside the sac) ⁴.

Prognosis: Most of placental cysts carry a benign nature and prognosis, however, their presence has been considered by some as an ominous sign when attached near the umbilical cord insertion, as the risk for umbilical cord constriction increases and this may cause fetal growth retardation and intrauterine fetal asphyxia⁷.

Management: Usually no alteration of the obstetrical management is indicated.

Cysts are usually subchorionic (under the fetal plate), or sometimes within the placental tissue (Septal cyst) ³. Antenatally detected placental cysts were usually benign, simultaneous samples of cyst fluid, amniotic fluid, cord blood, and maternal blood (collected 3 hours before delivery), and biochemical measurements of cyst fluid, amniotic fluid, cord serum, and maternal serum suggested by many authors that, the solutes of cyst fluid do not originate exclusively from a single source⁸.

Pathogenesis: In addition, X- cell synthesis and secretion into the cyst fluid may occur¹.

Histopathological diagnosis proved their origin from the trophoplastic X cells, and confirm their frequent benign nature¹. Some authors stated that some of these cysts proved to be massive main stem villous hydrops with cisternal formation with no evidence of trophoplastic hyperplasias⁶. In doubtful cases, placental mosaicism for triploidy should be excluded by DNA flow cytometry⁶.

Common associations: Placental cysts occur frequently in Diabetes Mellitus or maternal fetal rhesus incompatibility³.

There are records also of their association with the following cases:

1. Beckwith –Wiedemann syndrome⁵
2. Hemochromatosis⁵
3. Intrauterine growth retardation⁷
4. McCune –Albright syndrome⁵
5. Cytochrome B 450 (subfamily XIX); CYP 19⁵
6. Von Hippel-Lindau Syndrome; VHL⁵
7. Mucopolysaccharidosis (Type I) ⁵
8. Apolipoprotein (a); LPA. ⁵
9. Protein C deficiency, congenital thrombotic disease⁵
10. Glutaric aciduria ILA⁵
11. Zellweger syndrome; ZS⁵
12. partial molar pregnancy and fetal rubella⁵

References:

1-Ferrara N, Menditto C, DiMarino MP, Ciccarelli A, Gerosolima G, Menditto V . Subchorionic placental cysts : Histopathological and clinical aspects in two cases. Pathologica 1996 Oct; 88 (5):43943.

2- Heredia, Partial Mole + Fetal Rubella www.thefetus.net/.

3- www.IndianRadiologist.com.

4- Kramar, www.thefetus.net/.

5- On line Mendelian Inheritence in Man.

6- Pridmore BR, Khong TY, Wells WA, Ultrasound placental cysts associated with massive placental stem villous hydrops, diploid DNA content, and exomphalos .Am J Perinatol 1994 Jan; 11 (1) :14-8

7- Raga F, Ballester MJ, Osborne NG, Bonilla–Musoles F. Subchorionic placental cyst: a cause of fetal growth retardation – ultrasound and color flow Doppler diagnosis and follow up. J Natl Med Assoc 1996 May; 88 (5): 285-8.