Fig. 1

a CT, performed 2 months before diagnosed with pneumothorax, showed bullae lesions at the edge of the right upper lobe and right lower lobe (arrow). b Intraoperative findings demonstrated fibrinopurulent empyema. c Chest X-ray showed expanded right lung; however, dark-red pleural effusion of more than 500 ml per day continued. d Pathological findings showed atypical spindle-like cells infiltrating the parietal pleura (arrows). Erythroblast transformation-specific-related gene (ERG) was positive in tumor cells, suggesting the differentiation of endothelial cells