Answer for BIR CoW 01 Dec 2024
Bronchogenic cyst
Findings
Discussion
Bronchogenic cysts are congenital malformations of the bronchial tree, classified as bronchopulmonary foregut malformations. They commonly present as mediastinal masses and may cause local compression.
Epidemiology
Differential Diagnosis (DD)
Findings
- Chest X-Ray (PA and Lateral Views):
- Evidence of superior mediastinal widening.
- Loss of the right paratracheal stripe.
- Positive cervicothoracic sign.
- Suggestive of a posterior mediastinal mass.
- CT Scan (Axial Images):
- Well-defined cystic lesion in the posterior mediastinum displacing the trachea anteriorly.
- Lesion abuts the posterior border of the trachea and extends inferiorly to the carina.
- Fat plane between the esophagus and lesion remains intact.
- MRI Findings:
- T1 Images: Hypointense lesion in the posterior mediastinum.
- T2 Images: Hyperintense lesion displacing the trachea anteriorly, abutting its posterior border, and extending inferiorly to the carina.
- T2 Sagittal/Coronal Images: Lesion extends along the posterior wall of the trachea in the posterior mediastinum.
- DWI: No evidence of diffusion restriction.
Discussion
Bronchogenic cysts are congenital malformations of the bronchial tree, classified as bronchopulmonary foregut malformations. They commonly present as mediastinal masses and may cause local compression.
Epidemiology
- Rare congenital lesions, constituting 5-10% of pediatric mediastinal masses.
- Equal distribution between sexes for mediastinal cysts, but intrapulmonary cysts show male predilection.
- Result from abnormal budding of the bronchial tree during embryogenesis (4th-6th weeks).
- Lined with secretory respiratory epithelium (cuboidal or columnar ciliated).
- Wall components resemble normal bronchial tissue, including cartilage, elastic tissue, mucous glands, and smooth muscle.
- Cysts typically contain fluid, proteinaceous material, blood products, or calcium oxalate, and do not usually communicate with the bronchial tree.
- Mediastinal (~70%):
- Most common in the middle mediastinum (65-90%).
- Frequently found in subcarinal, right paratracheal, and hilar areas.
- Approximate incidence:
- Carinal area: ~50%
- Paratracheal area: ~20%
- Oropharyngeal wall: ~15%
- Retrocardiac area: ~10%
- Parenchymal (Intrapulmonary):
- Typically perihilar, with a lower lobe predilection.
- Uncommon Locations:
- Neck
- Cutaneous
- Pericardium
- Across the diaphragm (dumbbell-shaped)
- Retroperitoneal (often left-sided).
- Plain Radiograph:
- Rounded soft-tissue density structures.
- Compression of surrounding structures, occasionally causing air trapping or hyperlucent hemithorax.
- Calcific density material ("milk of calcium") may occasionally be visible.
- CT Scan:
- Well-circumscribed, spherical/ovoid masses with variable attenuation depending on fluid composition.
- 50% have fluid density (0-20 HU); others may exhibit soft tissue or higher attenuation.
- No solid contrast enhancement.
- MRI:
- T1: Variable signal intensity (low for fluid, high for proteinaceous content).
- T2: Usually hyperintense due to fluid content.
- Fluid-fluid levels may be observed.
- Fistula formation with the bronchial tree.
- Cyst wall ulceration.
- Secondary bronchial atresia.
- Superimposed infection.
- Hemorrhage.
- Rare malignant transformation (~0.7%), including:
- Rhabdomyosarcoma.
- Pleuropulmonary blastoma.
- Anaplastic carcinoma.
- Leiomyosarcoma.
- Adenocarcinoma.
Differential Diagnosis (DD)
- Congenital cysts/malformations:
- Pericardial cyst
- Cystic hygroma/lymphangioma
- Neurenteric cyst
- Esophageal duplication cyst
- Thyroid colloid cyst
- Thymic cyst
- Other:
- Intrathoracic pancreatic pseudocyst
- Anterior/lateral meningocele
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!