Granulomatous inflammation diagnosed by fine-needle aspiration biopsy

Fine-needle aspiration biopsy (FNAB) is a minimally invasive biopsy technique and an important tool for diagnosing infectious diseases. Rapid onsite evaluation allows for triage for ancillary testing, including microbiologic cultures. We aimed to determine the etiology of granulomatous inflammation diagnosed by FNAB by correlating with culture results and clinical history.

A 16-year retrospective review of cases diagnosed as "granulomatous inflammation" or "granuloma" was performed at the Departments of Pathology at the Zuckerberg San Francisco General Hospital and Trauma Center and University of California, San Francisco.

A total of 339 FNABs diagnosed as granulomatous inflammation were identified. Necrotizing granulomatous inflammation was present in 117 of 339 cases (34.5%) and non-necrotizing granulomatous inflammation was present in 222 of 339 cases (65.5%). A pathogen was detected in 100 of 339 (29.5%) FNABs by either cytomorphology, special stains, or culture, or a combination of more than one test. Of the 100 pathogen-positive cases, necrotizing granulomatous inflammation was seen in 50 of 100 (50%) and non-necrotizing granulomatous inflammation was identified in 50 of 100 (50%) cases. Culture results were available in 239 cases and positive in 70 (29%). Positive culture results included 40 of 239 (17%) cases with Mycobacterium tuberculosis complex, 15 of 239 (6.3%) with atypical mycobacterial species, 6 of 239 (3%) with Coccidioides immitis, 2 of 239 (<1%) with Histoplasma capsulatum, and 2 of 239 with Talaromyces marneffei (<1%).

Granulomatous inflammation is a nonspecific finding and suggests a broad range of disease processes, ranging from infection to malignancy. FNAB is an excellent minimally invasive technique that allows for ancillary testing critical for definitive diagnosis.