[A case of M. fortuitum lung disease with small-cell lung cancer]

A 58-year-old man was admitted to our hospital because of an abnormal shadow found on chest radiography. Chest radiographs and chest CT on admission showed a bulla with a niveau and infiltration in the right upper lobe. Smear of sputum and bronchial lavage were negative for acid-fast bacilli. Despite treatment with meropenem and clindamycin, the infiltrating shadow worsened. Since bronchial lavage and sputum culture were positive for M. fortuitum, these drugs were replaced with minocycline and imipenem. Thereafter, the shadow on the chest radiograph improved. After discharge, outpatient treatment with clarithromycin and levofloxacin was continued. After 4 months, the residual tumor shadow in the right upper lobe gradually grew. When a CT-guided transcutaneous needle lung biopsy was undertaken, malignant cells were found. Right upper lobectomy was performed. Pathological examination of the lesion demonstrated small-cell lung cancer. If a lesion does not change after nontuberculous mycobacteria treatment, the physician should consider other lesions such as lung cancer.