Development of Squamous Cell Carcinoma Following Complete Resolution of Mycobacterium xenopi Pulmonary Infection - Case Report

Background: Mycobacterium xenopi is a slow-growing, nontuberculous mycobacterium (NTM) capable of causing pulmonary infections, often mimicking tuberculosis. Case Presentation: A 56-year-old man with a 30-pack-year smoking history and rheumatoid arthritis on methotrexate and infliximab presented with a persistent cough and fatigue. Imaging revealed a cavitary lesion in the right upper lobe. Transbronchial biopsy culture grew M. xenopi . He was treated with moxifloxacin, azithromycin, ethambutol, and rifampin with complete resolution after 18 months of therapy. Repeat CT scan of the chest showed a new small, spiculated mass (15.37 mm x 11.79 mm) at the same site. Transbronchial biopsy showed squamous cell carcinoma on pathology, followed by lobar resection with clean margins. Patient is doing well 6 years later. Conclusion: This case highlights a rare occurrence of carcinoma developing at a prior M. xenopi infection site. Although causality remains unproven, it underscores the importance of post-infection surveillance in high-risk patients.