A 58-year-old man from Delhi presents with progressive dyspnea and right-sided pleuritic chest pain for 3 weeks. He has a 40 pack-year smoking history and weight loss of 8 kg over 2 months. On examination, breath sounds are diminished over the right lower lobe. Chest X-ray shows a right-sided pleural effusion. Thoracentesis is performed and pleural fluid analysis shows: protein 4.2 g/dL, LDH 450 IU/L, glucose 35 mg/dL, pH 7.1, and ADA (adenosine deaminase) 8 U/L. Serum protein is 6.8 g/dL and serum LDH is 280 IU/L. What is the most likely diagnosis?