“…The most common application of cytology in benign pulmonary lesions is for the detection of lung infections, especially for immunocompromised patients including HIV/AIDS patients, patients with known malignancies, and transplant patients. To increase the accuracy and sensitivity of the cytology specimens, typically bronchoalveolar lavages (BAL) or bronchial washings but occasionally induced sputa or more rarely lung FNAs, a multimodal assessment for infectious organisms, including cultures, various pathogen specific histochemical stains (eg, Ziehl‐Nielsen stain for mycobacterium), immunohistochemistry, and molecular detection, is recommended in addition to obtention of clinical history and correlation with corresponding tissue biopsies . In such specimens from immunosuppressed patients, one must look most particularly for fungi (including Pneumocystis jiroveci ) and for viral changes.…”