| Smooth, well-defined margins |
The lesion has round or oval contours without spiculation or irregularity |
Suggests a benign etiology (e.g., hamartoma, granuloma) |
| Central or popcorn calcification |
Coarse, chunky calcifications often centrally located |
Classic for pulmonary hamartoma |
| Fat within the lesion |
Areas of negative Hounsfield units (-50 to -100 HU) within the mass |
Strongly suggestive of hamartoma |
| Stable size over ≥2 years |
No significant growth in diameter over long-term follow-up |
Indicates likely benign behavior |
| Small size (<6 mm) |
According to Fleischner guidelines, nodules <6 mm in low-risk individuals rarely require follow-up |
Low probability of malignancy |
| Lack of contrast enhancement |
Benign nodules often enhance <15 HU on contrast-enhanced CT |
Used in indeterminate nodules; low enhancement suggests benignity |
| Lamellated or concentric calcification |
Target-like calcified pattern |
Often seen in healed granulomas (e.g., histoplasmosis, TB) |
| Subpleural location without pleural tail |
Peripheral location without invasive features |
May support benignity depending on other features |
| Air bronchogram within nodule |
Air-filled bronchi traversing the lesion |
Rare but can be seen in benign conditions (also seen in adenocarcinoma) |
| Satellite nodules |
Small nodules clustered near a dominant nodule |
Often seen in benign granulomatous infection (e.g., histo) |
