Uploaded May 2026 | Updated September 2026, 1 week ago

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A 77-year-old man with a 50 pack-year smoking history and history of pulmonary tuberculosis underwent bronchoscopy for evaluation of suspected lung cancer. During bronchoscopy, areas of black discoloration were seen on the mucosa of the left main bronchus. A biopsy sample showed ciliated respiratory epithelium with subepithelial accumulation of macrophages containing black pigment. What is the most likely cause of these findings? Submit your answer at NEJM.org.

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