Placental chorioangiomas are benign vascular tumours of placental origin. It is the most common tumour of the placenta and is usually found incidentally.
The estimated incidence is at ~1% of all pregnancies 3.
In most cases, chorioangiomas are asymptomatic, and merely incidental findings. Occasionally, when they are large or multiple, they can result in poor outcomes for both the fetus and the mother.
A chorioangioma is thought to arise as a malformation of the primitive angioblastic tissue of the placenta. 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 platelets and can, in turn, give a fetal thrombocytopenia.
There is some debate as to the exact nature of chorioangiomas. Most authors consider them as a benign neoplasm while others, however, categorise them as hamartomas, given their composition of mostly native placental tissue and their inability to metastasise.
There can be significant variation in size. Most lesions tend to small and lesions >4 cm are rare 8. Large tumours can, however, produce degenerative phenomena like necrosis, calcification, hyalinisation, or myxomatous degeneration.
Three histological types are recognised:
- angiomatoid: characterised by numerous blood vessels
- cellular: with poor vascularisation
Most cases tend to be sporadic.
They tend to occur on the fetal side of the placenta (close to cord insertion).
Recognised associations include:
- Beckwith-Wiedemann syndrome
- single umbilical artery
- fetal anaemia
- fetal congestive cardiac failure
- hydrops fetalis: also listed under complications
- polyhydramnios: also listed under complications
Typically a chorioangioma is located near the insertion of the cord and protrudes into the amniotic cavity.
- often seen as a hypoechoic, rounded mass, located near the chorionic plate +/- umbilical cord insertion site
- it usually contains anechoic 'cystic' areas and can be seen as distinctly separate to normal surrounding placental tissue
- some heterogeneous areas caused by degenerative processes and internal haemorrhage can be seen
- chorioangiomas can also rarely appear pedunculated
- Doppler: often demonstrates low resistance pulsatile flow within the anechoic 'cystic' areas, which represent enlarged vascular channels
Large chorioangiomas may undergo spontaneous infarction with decreased echogenicity, decreased tumour volume, and decreased blood flow on colour Doppler images 6.
MRI usually demonstrates a heterogeneous mass. Signal characteristics include:
- T1: isointense to placenta if uncomplicated can be hyperintense if there has been a haemorrhage
- T2: high signal intensity; can be heterogeneous, an appearance similar to that of a haemangioma 6
Treatment and prognosis
Chorioangiomas are usually treated with expectant management, as the majority of tumours are asymptomatic. Small tumours are often monitored with ultrasound ~every 6-8 weeks, whereas large tumours require serial ultrasound examinations more frequently ~every 1-2 weeks. Some tumours may even regress spontaneously during pregnancy 12.
The overall prognosis is somewhat dependent on the presence or development of hydrops fetalis. In general, lesions larger than 4 cm are considered to produce haemodynamic effects on the fetus 3. Therapeutic amnio-drainage is an option if there is excessive polyhydramnios.
Vascular shunting may cause fetal high-output cardiac failure and hydrops fetalis.
Other complications include:
- premature labour
- fetal thrombocytopenia
- intrauterine growth restriction (IUGR)
- placental abruption
History and etymology
They were thought to have been first described by Clarke in 1798 13.
For ultrasound appearances consider:
- subamniotic haematoma
- partial hydatidiform mole
- submucosal uterine fibroid: sub-mucosal leiomyoma of the uterus
- placental teratoma
- atypical placental venous lake: on greyscale imaging
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