What are the differences between a placental chorangioma and placental lacunae, and how do they appear differently on ultrasound?

Chorangioma vs Placental Lacunae: Key Differences

Chorangiomas and placental lacunae are fundamentally different entities—chorangiomas are benign vascular tumors of the placenta, while lacunae are sonolucent spaces within the placental parenchyma that represent pathologic vascular channels associated with placenta accreta spectrum.

What They Are

Chorangioma

• Benign non-trophoblastic vascular tumor arising from primitive chorionic mesenchyme 1
• Occurs in approximately 1% of pregnancies 1
• Most are small (<4 cm) and clinically insignificant
• Giant chorangiomas (≥4-5 cm) are rare (1/3500 to 1/9000 pregnancies) and associated with maternal-fetal complications 2

Placental Lacunae

• Pathologic vascular spaces within placental parenchyma, not tumors 3
• Form from distortion of placental lobules developing inside uterine scars 3
• Result from high-volume, high-velocity blood flow from radial/arcuate arteries 3
• Strongly associated with placenta accreta spectrum (present in >80% of cases) 4

Ultrasound Appearance Differences

Chorangioma on Ultrasound

• Well-circumscribed, round/oval mass with clear borders 5, 6
• Usually located on the fetal surface of the placenta (near umbilical cord insertion) 7
• Appears as hypoechoic or hyperechoic solid mass 7
• Identifiable feeding vessel on color Doppler—this is the key distinguishing feature 6, 7
• Shows internal vascularity with organized blood flow pattern
• Typically a single, discrete lesion 1

Placental Lacunae on Ultrasound

• Multiple irregular sonolucent (anechoic) spaces scattered throughout placenta 8
• Appear as "Swiss cheese" pattern within placental tissue 4
• No discrete borders or capsule—blend into surrounding placenta 3
• Show turbulent, chaotic blood flow on color Doppler (not organized feeding vessels) 4
• Associated with loss of retroplacental clear zone and other accreta signs 4, 8
• When multiple, large, and irregular = highly suggestive of placenta accreta 8

Clinical Context Matters

Chorangioma Context

• Can occur in any pregnancy (no specific risk factors required)
• Associated with polyhydramnios (60%), cardiomegaly (25%), fetal growth restriction 7
• Requires monitoring for fetal anemia, hydrops, high-output cardiac failure 1, 9

Lacunae Context

• Always consider placenta accreta spectrum when lacunae are present 4
• Look for risk factors: prior cesarean delivery, placenta previa, anterior placenta 4, 10
• Lacunae have highest sensitivity and positive predictive value for accreta in second trimester 8

Common Pitfalls to Avoid

1. Don't confuse lacunae with normal placental lakes: Normal lakes are benign, variable-sized anechoic areas with slow flow, found in normal placentas. Lacunae are irregular, multiple, with turbulent flow and associated with uterine scarring 3

2. Don't miss the feeding vessel: If you see a well-defined mass with a clear feeding vessel on Doppler, think chorangioma, not lacunae 6

3. Don't ignore clinical context: Lacunae in a patient with prior cesarean and anterior placenta previa = accreta until proven otherwise 4, 10

4. Don't rely on a single finding: When evaluating for accreta, look for the complete picture—lacunae plus loss of clear zone, thin myometrium (<1 mm), bladder abnormalities 4, 8