Cavitary lung lesion suspicious for malignancy reveals Mycobacterium xenopi

A Case Series of Non-Tuberculous Mycobacterial Pulmonary Disease Masquerading as Malignancy From a Community-Based Hospital

Non-tuberculous mycobacteria (NTM) are ubiquitous organisms in the environment that can potentially cause a range of pulmonary and extrapulmonary infections in humans. Epidemiological risk factors and the host's immune status determine the susceptibility to various clinical syndromes caused by different NTM species. Non-tuberculous mycobacteria pulmonary disease (NTM-PD) is primarily reported in patients with underlying lung disease. These infections often pose a significant disease burden on affected patients as they are often chronic, difficult to treat, and necessitate long-term multi-drug therapy. Mycobacterium avium complex (MAC) is the most common causative pathogen of NTM-PD in the USA, followed by Mycobacterium kansasii (M. kansasii). Less common species in the USA include Mycobacterium xenopi (M. xenopi), Mycobacterium abscessus, and others, largely depending upon the geographic location and exposure to species-specific predisposing risks. In this case series, the authors report on three elderly patients with chronic lung diseases who had pulmonary NTM disease caused by M. xenopi and MAC. The patients were encountered in both inpatient and outpatient settings from a community-based hospital in the midwestern USA. The clinical and radiological features of NTM-PD masqueraded as malignancy and posed a diagnostic dilemma. The epidemiology, clinical and radiological features, diagnosis, and management of NTM-PD are reviewed in this report.

Imaging characteristics of nontuberculous mycobacterial pulmonary nodules

Introduction: Nontuberculous mycobacteriosis (NTM) of the lungs can develop nodules. In order to clarify some of the characteristics of lung NTM nodules, we examined volume doubling time (VDT) and maximum standardized uptake value (SUVmax) in positron emission tomography (PET) of pathologically diagnosed NTM nodules.Methods: From November 2012 to August 2018, clinical and radiological information were retrospectively investigated in 8 patients who were surgically resected and diagnosed as NTM. These eight patients were followed up until November 2020 and were confirmed to have no appearance of lung cancer or reappearance of lung NTM nodules. The VDT was calculated using the Schwartz formula.Results: The median maximum diameter of the nodule at the time of the first CT scan was 16.0 (range: 9.9-20.0) mm. The median maximum diameter of the nodule on CT performed before the surgical biopsy was 18.8 (range: 10.4-32.8) mm. The median doubling time calculated from these results was 203 (range: 20-568) days. Caseous granulomas and acid-fast bacilli were histologically confirmed in all 8 patients. Culture of excised nodules revealed Mycobacterium intracellulare in 5 patients and Mycobacterium avium in 3 patients. Six patients received PET, and median SUVmax was: 7.0 (range: 3.3-21.0). Median VDT was around 200 days. Some patients had irregular-shaped nodules.Conclusions: CT/PET-CT characteristics of lung nodules are not reliable in differentiating lung NTM nodules from malignant ones. To avoid unnecessary resection, it may be better to collect various information on imaging findings in the nodule itself and in opacities other than the nodule.