False-positive sputum cytology in a case of pulmonary infarction

Sputum cytology is an important diagnostic tool in pulmonary medicine, but it can yield a false-positive diagnosis of malignancy. We describe such a case, which involved a 70-year-old man who presented with chest pain, hemoptysis, and bilateral pulmonary infiltrates. In the initial evaluation of hemoptysis, multiple sputum samples demonstrated cytological abnormalities consistent with adenocarcinoma, but bronchoscopy found no evidence of malignancy. He was ultimately found to have pulmonary thromboembolic disease with infarction. Follow-up radiographs showed resolution of the pulmonary infarcts, and the absence of malignancy was proven during postmortem examination. Pulmonary infarction is one of many diseases that can produce sputum cytological findings falsely indicative of malignancy.