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Differential diagnosis of Langerhans cell histiocytosis.
Nodular LCH:
- Sarcoidosis: perilymphatic distribution.
- Metastases: random distribution.
Cystic LCH:
- LAM: round
Cystic LCH: - LAM ... : round cysts, evenly ... child-bearing age - Cystic ... ring sign'. - Centrilobular ... #Cysts #Differential
Low Attenuation pattern (2) 
1. Centrilobular emphysema: low attenuation areas without walls. Notice the centrilobular artery
Centrilobular emphysema ... Notice the centrilobular ... multiple thick walled cysts ... (LAM): regular cysts ... LowAttenuation #Cystic
Low Attenuation pattern 
1. Lymphangiomyomatosis (LAM): uniform cysts in woman of child-bearing age; no history of
(LAM): uniform cysts ... bizarre shaped cysts ... Centrilobular emphysema ... LowAttenuation #Cystic
Differential diagnosis of Lymphangiomyomatosis:
Langerhans cell histiocytosis: > 90% are smokers, cysts have irregular shapes and the
90% are smokers, cysts ... Centrilobular emphysema ... perceptible wall, centrilobular ... Lymphangiomyomatosis #LAM #Cystic
Tree in Bud Sign
The Tree-in-Bud sign represents Endobronchial spread in a linear branching pattern and centrilobular
branching pattern and centrilobular ... surrounded by centrilobular ... congenital causes like cystic
HRCT findings in Langerhans cell histiocytosis:
Early stage:
- Small irregular or stellate nodules in centrilobular location.
Late stage
stellate nodules in centrilobular ... commonly seen) - Cystic ... airspaces Cysts ... There are no cysts
On the left some diseases with a nodular pattern.
1. Hypersensitivity pneumonitis: ill defined centrilobular nodules.
2. Miliary
pneumonitis: ill defined centrilobular ... Hypersensitivity pneumonitis: centrilobular ... before the typical cysts ... bronchiolitis: ill defined centrilobular
High-Res Chest CT Patterns - Differential Diagnosis Framework
Reticular:
 • Septal Thickening: Lymphangitic Carcinoma, Interstitial Edema, Alveolar
Pneumoconiosis • Centrilobular ... Antitripsyn Def • Cysts ... Infection, Aspiration, Cystic
Emphysema, when it is severe, can mimick Langerhans cell histiosytosis.
When it extends beyond the centrilobular area
extends beyond the centrilobular ... look as if it is cystic
Basic Interpretation
A structured approach to interpretation of HRCT involves the following questions:
What is the dominant HR-pattern:
reticular
nodular
high
attenuation (emphysema, cystic ... secondary lobule (centrilobular