Mediastinal bronchogenic cyst
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A large (5.8 x 5.1 x 5.2 cm) round well-defined thin-walled cystic mass containing homogeneous fluid density content is seen arising in right hilar region, invaginating between horizontal & oblique fissures, compressing middle lobe anteriorly & laterally, and splaying pulmonary vessels.
No mural or internal calcification, hemorrhage or septations are seen.
After administration of I/V contrast, no mural, internal or perilesional enhancement is noted. No solid component is present.
Airspace densification with internal air bronchograms is noted in lateral segment of middle lobe, representing atelectasis due to compression.
Ground-glass haziness is noted in rest of the middle lobe around the cyst.
Lower part of oblique fissure is bowed upwards, due to atelectasis in middle lobe.
Few prominent lymph nodes are seen in right paratracheal region.
Intrapulmonary bronchogenic cyst
Is this cyst mediastinal or intrapulmonary in location?
Although not in the characteristic location of either (carina for mediastinal, right lower lobe for pulmonary), this cyst still demonstrates adequate characteristics to be identified as a mediastinal bronchogenic cyst.
# Both axial and coronal images show obtuse angulation between the cyst at the medial surface of the lung, which denote extrapulmonary location.
# Coronal images also show the cyst coming in direct contact with the superior vena cava and upper part of right atrium, as well as with lymph nodes.
# There is no lung tissue (thinned / atelectatic / ventilated) overlying the medial surface of the cyst — rather it comes in direct contact with mediastinal structures as noted above.
The foremost differentials for mediastinal cysts at this age could be germ cells tumors (seminoma, teratoma etc). Absence of solid components, calcifications etc make teratoma a weaker possibility. Female gender almost excludes teratoma.
Distance from esophagus excludes duplication cyst, and distance from vertebral column excludes neuroenteric cyst. It is also away from thymus and pericardium.
CT is often adequate imaging for diagnosis, and treatment may not be necessary unless the cyst creates critical compressive symptoms, or demonstrates malignant changes.
- 1. Gurney, J et al (2007). Diagnostic imaging: Chest. Salt Lake City: Amirsys, pp.II-1-2 to II-1-5.