Fig. 4

a–d CT images of lung adenocarcinoma. a CT image shows a small nodule (5 mm) beside a blood vessel in the right upper lobe. b Eight months later, its size increased (10 × 11 mm) but its density was heterogeneous. c Fifteen months later, its size significantly increased (18 × 19 mm); furthermore, its density increased, and it became more homogeneous. Additionally, lobulation sign and peripheral vascular convergence (red circle) were positive. d Histopathologic analysis of the resected nodule revealed invasive adenocarcinoma