False-positive cytological diagnosis of lung carcinoma in patients with pulmonary infarcts.

Cytological examination of specimens obtained from the tracheobronchial tree has become an integral part of the evaluation of pulmonary lesions. Cytological criteria for the diagnosis of carcinoma exist and are well defined. Certain benign processes, however, may possess features strongly suggestive of carcinoma of the lung. We report 3 patients in whom a positive cytological diagnosis of carcinoma of the lung was made by an experienced cytopathologist. At operation each patient was found to have pulmonary infarct and no evidence of carcinoma. Review of this experience has disclosed cytological and clinical features that should alert the clinician to the possibility that the cytological diagnosis of lung cancer may be misleading in certain nonmalignant diseases.