A 52-year-old man with a 10-year history of rheumatoid arthritis presents with progressive dyspnea and pleuritic chest pain for 3 weeks. Examination reveals reduced breath sounds at the right base. Chest X-ray shows a moderate right-sided pleural effusion with an underlying opacity in the right lower lobe. Thoracentesis yields exudative fluid with low glucose (18 mg/dL), elevated LDH (850 IU/L), and low complement levels. Which imaging feature on CT chest would be most specific for the underlying diagnosis?