Outcome of untreated lung nodules with histological but no microbiological evidence of tuberculosis

The outcome of lung nodule(s) with histopathological findings suggestive of tuberculosis (TB) but lack of microbiologic confirmation remains unclear. Whether these patients require anti-TB treatment remains unknown. The aim of the study was to compare the risk of active TB within 4 years in untreated patients with histological findings but no microbiological evidences suggestive of TB.

From January 2008 to June 2013, patients with either solitary or multiple lung nodules having histological findings but no microbiological evidences suggestive of TB were identified from a medical center in Taiwan and were followed for 4 years unless they died or developed active TB.

A total of 107 patients were identified. Among them, 54 (51%) were clinical asymptomatic. Biopsy histology showed granulomatous inflammation in 106 (99%), and caseous necrosis was present in 55 (51%) cases. Forty (37%) patients received anti-TB treatment, and 21 (53%) of them had adverse events, including 13 initially asymptomatic patients. Anti-TB treatment was favored in patients with caseous necrosis, whereas observation was preferred in subjects whose nodules were surgically removed. Only 1 case in the untreated group developed culture-confirmed active pulmonary TB during 4-year follow-up (1 case per 251.2 patient-years). None of the 16 cases having co-existing histologic finding of malignancy became incident TB case within a follow-up of 56.7 patient-years.

In patients having lung nodules with only histologic features suggestive of TB, the incidence rate of developing active TB was low. Risk of adverse events and benefit from immediate treatment should be carefully considered.