Pneumonia and carcinoma of the lung.

In a prospective study of 1269 patients with community-acquired pneumonia, 25 (1.97%) were found to have carcinoma of the lung. In 23 cases, the diagnosis was confirmed histologically. For nine of the 23 patients, this episode of pneumonia was the initial manifestation of carcinoma of the lung. The diagnosis of carcinoma was first suggested by the radiologist as the result of a chest radiograph in five of the nine cases. One patient with bronchoalveolar cell carcinoma presented with rapidly progressive diffuse airspace disease. The diagnosis in this case was made by means of open lung biopsy. Two of the 25 patients (8%) had pneumonia caused by Coxiella burnetii, a rate that was 2.4 times higher than that for the other patients with pneumonia. We conclude that pneumonia is uncommonly the presenting manifestation of carcinoma of the lung but is usually evident before the patient leaves hospital. The rate of pneumonia caused by C. burnetii among patients with carcinoma of the lung seems to be higher than that among patients who have pneumonia without carcinoma of the lung.