Usefulness of lymphoid granulomatous inflammation culture obtained by endobronchial ultrasound-guided transbronchial needle aspiration in a fungal endemic area

Background and Objectives: Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is the procedure of choice for the evaluation of mediastinal/hilar lymph node enlargements. Granulomatous inflammation of the mediastinal/hilar lymph nodes is often identified on routine histology. In addition, mediastinal lymphadenopathy may be present with undiagnosed infection. We sought to determine the usefulness of routine cultures and histology for infectious etiologies in a fungal endemic area when granulomatous inflammation is identified. Materials and Methods: We identified 56 of 210 patients with granulomatous inflammation on EBUS-TBNA biopsies from October 2012 through October 2014. An onsite cytologist evaluated all biopsies and an additional TBNA pass for microbiologic stains and cultures were obtained in those with granulomatous inflammation. Results: Of the 56 patients with granulomatous inflammation, 20 patients had caseating (necrotizing) granulomas while noncaseating (nonnecrotizing) granulomas were detected in 36 of the remainder patients. In patients with caseating granulomas, fungal elements were identified in 6 of 20 (30%) patients (histoplasma; N = 5, blastomyces; N = 1) on Grocott methenamine silver (GMS) stain. Lymph node cultures identified 3 of 20 (20%) patients as being positive for Mycobacterium tuberculosis (N = 1), Histoplasma capsulatum (N = 1), and Blastomyces dermatitidis (N = 1). Among patients with noncaseating granulomas, only 2 out of 36 (5%) were positive for fungal elements on GMS stain, identified as Histoplasma, although the lymph node cultures remained negative. Conclusion: The incidence of granulomatous inflammation of mediastinal lymph nodes was 26.6% in our series. Of these patients, noncaseating granulomas were more common (64% vs. 36%). Infectious organisms, fungal or acid-fast bacilli (AFB), on either staining or lymph node culture were rarely identified in noncaseating granulomas, 5% and none, respectively. Caseating granulomas were more commonly associated with positive lymph node fungal stain and culture, 35% and 15%, respectively. In a fungal endemic area, lymph node staining and culture can be considered in cases with caseating granulomatous inflammation, if known at the time of biopsy.