Primary Malignant Melanoma of the Lung With a Long-Term Course: A Case Report.

A 66-year-old man with a 20-year history of recurrent haemoptysis presented with mild bronchiectasis and linear opacities detected on chest computed tomography (CT). The lesion was followed up annually and gradually enlarged into a mass over 10 years. Multiple bilateral pulmonary nodules were noted at 78 years of age. Surgical biopsy revealed malignant melanoma without evidence of other primary lesions on dermatological examination or positron emission tomography-CT. The patient was treated with nivolumab and achieved stable disease for 8 months before discontinuation owing to immune-related adverse events. Rapid disease progression was observed, and the patient died 14 months after initiating immunotherapy. Autopsy demonstrated extensive metastatic dissemination and marked tumour necrosis with CD8+ T-cell infiltration in the lung tumour, indicating a therapeutic response to nivolumab. These findings highlight the potential association between chronic airway inflammation and tumour development and suggest that immunotherapy could play a role in treating PMML.