Emphysema vs. cyst: Emphysema = low attenuation areas without a defined wall — does not require cyst workup. Centrilobular core structures (bronchial artery, bronchiole, intralobular septa) are spared in emphysema and displaced in cystic lung disease.
Cysts with a nodular component abutting the wall (Sheard Types I–III) require further evaluation given association with cystic lung cancer.
Reporting Elements
- Presence or absence of a wall
- Wall thickness (thin vs. thick >2 mm)
- Single vs. multiple
- Distribution
Algorithm — Cyst Distribution
| Distribution | Associated Findings | Diagnosis to Consider | Action |
|---|---|---|---|
| Upper lung predominance; cysts sparing bases | Nodules may be present in same distribution | Pulmonary Langerhans Cell Histiocytosis (PLCH) | Pulmonary consultation |
| Diffuse cysts | — | LAM / Tuberous Sclerosis | Pulmonary consultation |
| Diffuse cysts, lower lung predominance | Ground glass attenuation in lower lungs | Lymphoid Interstitial Pneumonia (LIP); often with Sjögren's Syndrome | Pulmonary consultation |
| Diffuse cysts, lower lung predominance | Associated nodules | Amyloidosis / Light Chain Deposition Disease | Pulmonary consultation |
| Diffuse cysts, lower lung predominance | No associated abnormality | Birt-Hogg-Dubé Syndrome | Pulmonary consultation |
All patterns of cystic lung disease (perceptible walls, diffuse or lower-lung distribution, or associated findings) warrant pulmonary consultation for further workup.
References
Munden RF, Black WC, Hartman TE, et al. Managing Incidental Findings on Thoracic CT: Lung Findings. A White Paper of the ACR Incidental Findings Committee. J Am Coll Radiol. 2021;18(9):1267–1279.