| Histology | HRCT |
| Smoker's macrophages within bronchiolar lumens and surrounding alveolar spaces, mild bronchiolar fibrosis and inflammation | Hazy centrilobular nodules Patchy ground-glass opacity |
| Mild distortion of bronchiolar lumens with bronchioloectasia and mucostasis | Mild bronchial dilatation with wall thickening; mild air-trapping at expiratory computed tomography scanning |
| Centrilobular and subpleural emphysema | Centrilobular and paraseptal emphysema |
| Dense interstitial fibrosis, frequently surrounding emphysematous holes | Peripheral and intralobular reticulation, ground-glass opacity intermingled with emphysematous areas |
| Increase in Langerhans’ cells forming stellate bronchiolocentric nodules, some of which are irregularly cavitated and fibrotic | Ill-defined or cavitated centrilobular nodules |