C78-37 Diagnostic Pitfalls With Bronchoalveolar Cytology

Abstract Introduction Diagnostic bronchoscopy allows direct visualization of the airways and collection of samples for microbiological, cytological, and immunological analysis. While cytology plays a crucial role in identifying malignant cells, false-positive results can occur in infectious or inflammatory conditions, posing a diagnostic challenge. Case Description A 56-year-old man with a 40 pack-year smoking history presented with two weeks of shortness of breath, hemoptysis, and chest pain. In the emergency department, his vital signs were: BP 96/64 mmHg, HR 100-110 bpm, RR 16, and temperature 98.3 °F. Chest X-ray revealed bilateral airway disease, prompting a CT scan, which demonstrated extensive bilateral infiltrates with a large cavitary lesion and air-fluid level in the right upper lobe—findings consistent with a cavitary abscess.As the patient was unable to expectorate sputum, bronchoscopy was performed for diagnostic sampling. It revealed severely inflamed and nodular mucosa in the anterior subsegment of the right upper lobe. Bronchoalveolar lavage (BAL) samples were collected for cytology and microbiology, and brushings were obtained given the mucosal nodularity. Cultures grew Streptococcus pneumoniae, and the patient was started on appropriate antibiotics. Cytologic evaluation of the BAL showed atypical cells suspicious for malignancy, though not definitive, whereas the brushings were negative. In the absence of a discrete endobronchial mass and given the clinical context of necrotizing pneumonia, the decision was made to continue antimicrobial therapy and reassess with imaging in 4-6 weeks. The patient improved clinically, and follow-up CT imaging demonstrated near-complete resolution of the pulmonary abscess and pneumonia, leaving only minimal residual scarring in the right upper lobe. He continues to do well on follow-up. The cytologic atypia was thus interpreted as reactive in origin due to severe infection. Discussion BAL cytology is a valuable tool in evaluating pulmonary malignancy but is not definitive. False-positive results may occur due to reactive epithelial changes, particularly type II pneumocyte hyperplasia and desquamation in response to alveolar injury and inflammation. These reactive atypical cells can closely mimic malignancy. In the setting of severe pneumonia and absence of a mass lesion, cytology should be interpreted with caution to avoid diagnostic errors and unnecessary interventions. This abstract is funded by: None