Analysis of pulmonary nodules caused by nontuberculous mycobacteriosis in 101 resected cases: multi-center retrospective study

BACKGROUND: Solitary pulmonary nodules caused by nontuberculous mycobacteriosis are included as a category of pulmonary nontuberculous mycobacterium disease. Clinical characteristics, treatments and prognosis are not fully known because there are a few related reports. METHODS: This was a multi-center retrospective study of 101 cases diagnosed as solitary nodular type of nontuberculous mycobacteriosis from January 2000 to March 2017 that underwent resection at 9 related facilities belonging to the Thoracic Surgery Study Group of Osaka. RESULTS: The most common pathogen was Mycobacterium avium complex (n=77, 87.5%), followed by Mycobacterium kansasii (n=8, 9.1%). Chest computed tomography results showed subpleural locations that were difficult to distinguish from lung cancer. Fluorodeoxyglucose positron emission tomography/computed tomography was performed in 58 cases and positive results were obtained in 35 (60.3%), with an average maximum standardized uptake value of 3.87. The purpose of resection in most cases was for diagnosis. The surgical procedure was wedge resection in 87, segmentectomy in 3, and lobectomy in 11, while 77 underwent thoracoscopic surgery. Postoperative complications occurred in 7 cases, though no infections caused by nontuberculous mycobacteriosis were noted. The median observation period was 27 months. A worsened condition occurred in 10 (9.9%) with Mycobacterium avium complex, though none had local recurrence. CONCLUSIONS: Solitary pulmonary nodules due to nontuberculous mycobacteriosis is difficult to diagnose based on preoperative examination results or distinguish from lung cancer. Among the present cases, none had local complications or recurrence, even in those that underwent a wedge resection, thus postoperative chemotherapy was not considered necessary if a complete resection was performed. On the other hand, some cases showed reinfection after a long period following resection, thus patients should be informed of that future possibility.