Infectious disease diagnosed by fine needle aspiration biopsy

Fine needle aspiration biopsies (FNABs) have become increasingly important in the assessment of infectious diseases. We assess the ability of cytopathology to predict the presence of a pathogen and review how often neoplasia occurs concurrently with infection.

A 3-year retrospective review of FNABs with concurrent culture results was performed at the Zuckerberg San Francisco General Hospital and Trauma Center. Rapid onsite evaluation was performed for all cases by a pathologist. The results of the special and immunohistochemical stains and polymerase chain reaction testing were correlated, when available.

A total of 231 samples from 11 different tissue sites were submitted for microbial culture, of which 49 (21%) were positive for pathogenic organisms. Only 2 false-negative cases by cytology were found in immunosuppressed patients. A total of 38 patients had a diagnosis of neoplasia, with 2 (5%) having concurrent infection. Overall, the sensitivity and specificity of cytology in predicting the presence of infection was 96% (95% confidence interval, 86%-100%) and 42% (95% confidence interval, 34%-50%), respectively. Molecular testing was performed in 11 cases, 2 of which were positive for Mycobacterium tuberculosis complex and had cytologic findings of necrosis. Polymerase chain reaction and other ancillary tests were unable to further characterize 2 cases with acid-fast bacilli.

Our study has shown that FNABs have high sensitivity in detecting infection and that negative cytology findings will correlate with a negative infectious workup. Although infection in the setting of neoplasia is uncommon, it should be considered if clinical data are available to suggest infection.