Rate of Infectious Etiologies in Patients with Necrotizing and Non-necrotizing Granulomas on Lung Biopsy

Background:  Limited data exist on the frequency of infectious etiologies among patients with necrotizing and non-necrotizing granulomas identified on histologic examination of lung tissue specimens.

Methods: We reviewed all adult patients who had necrotizing or non-necrotizing granulomas identified upon pathological examination of a lung biopsy specimen between January 2008 and July 2015. Demographic and clinical information was obtained through retrospective review of the patients’ medical records; we also reviewed all microbiology reports and results of radiological studies. The Pearson's chi-square test or the Fisher's exact tests were performed to compare categorical variables (P<0.05).

Results:  A total of 104 patients were included. The median age of the cohort was 59 (range 22 to 91) years, and 57 (55%) were male. A lung specimen was obtained by surgical exploration in 60 (58%) patients, 44 (42%) had a percutaneous biopsy. Thirty-two (31%) patients had a current or distant history of malignancy, 19 (18%) had diabetes mellitus, 11 (11%) chronic obstructive pulmonary diseases, and 22 (21%) were current smokers. Five (5%) patients received antibiotics within thirty days before biopsy. The most common radiological presentations were a pulmonary nodule (58%) or opacity (20%). On biopsy, a necrotizing granuloma was found in 30 (29%), a non-necrotizing in 74 (71%) patients. Tuberculosis (n=7) and non-tuberculous mycobacterial disease (n=13) was diagnosed in 20 (19%) patients, a fungal etiology (Aspergillus, Cryptococcus, or Blastomyces) was identified in 5 (5%) patients, one patient had Nocardia. Any infectious etiology was more common among patients with necrotizing granulomas (37%) than those with non-necrotizing granulomas (20%; P=0.08). The most common non-infectious etiologies were malignancy (18%) and sarcoidosis (17%).

Conclusion: An infectious etiology comprising mycobacteria, fungus, and Nocardia species was found among twenty-five percent of patients with granulomatous disease of the lung. Infection was found more frequently among patients with necrotizing than patients with non-necrotizing granulomas; however, the difference was not statistically significant.