What happened, in summary

This 74-year-old man was admitted with a 1-year history of persistent cough. He had smoked for 30 pack-years but had quit 20 years earlier. Contrast-enhanced chest CT showed an 11 × 10 cm right hilar mass causing bronchial narrowing and occlusion, enlarged mediastinal lymph nodes, inflammatory changes in the right lung, and right pleural effusion. Serum cytokeratin 19 fragment and CEA were elevated. Bronchoscopy showed external compression and obstruction of the right lower-lobe bronchus. EBUS-TBNA biopsy confirmed squamous cell carcinoma, with TTF-1-negative, NapsinA-negative, P40 3+, CK5/6 3+, Ki-67 10%+, CK7-positive, and CD34-negative staining. Pleural fluid cytology was negative, but pleural fluid CEA was markedly elevated at 128 ng/mL, raising strong suspicion for pleural metastasis. The cancer was staged cT4N3M1a, Stage IVA. Brain MRI showed only mild lacunar infarction, and bone scintigraphy plus rib MRI did not show bone metastases. He received albumin-bound paclitaxel, carboplatin, and camrelizumab every 3 weeks. After 2 cycles, imaging showed partial remission and mild interstitial changes. After 2 more cycles, he developed exertional dyspnea, high D-dimer, right lower pulmonary artery embolism, and worsening interstitial lung changes. Camrelizumab was stopped, and methylprednisolone plus enoxaparin were started. He completed a fifth chemotherapy cycle but then stopped methylprednisolone himself; follow-up CT showed new multiple right-lung pulmonary bullae. Methylprednisolone was restarted with a gradual 6-week taper, and a sixth chemotherapy cycle was completed. Follow-up CT showed marked improvement in both interstitial pneumonia and pulmonary bullae, supporting an immune-related pulmonary toxicity from camrelizumab rather than infection or chemotherapy-related lung injury.