ABSTRACT:Although roentgenographically occult lung cancer (ROLC) has been fully studied, there have been few reports dealing with occult cancers and negative sputum cytology. From 1975 to 1994, 100 patients were diagnosed with ROLC. Of these patients, 15 who had negative sputum cytology were examined retrospectively. The clinical characteristics, bronchoscopic findings, and pathologic findings of these patients were studied. Additionally, the tumor size, location, and bronchoscopic findings were compared with those of patients who had ROLC with positive sputum cytology. There were 17 lesions in 15 patients who had ROLC with negative sputum cytology. All cases of ROLC were detected by bronchoscopy during examination for other lung or laryngeal diseases. All of the patients were men with a high smoking index. Endoscopic examination showed that 10 lesions were the superficial thickening type; 5 were the nodular type; and 2 were the polypoid type. Average longitudinal extent of the lesions was 0.52 cm, which was significantly smaller than the lesions of the positive sputum cytology group (mean diameter; 1.28 cm, p < 0.01). In patients at high risk for lung cancer, if a diagnostic bronchoscopy is performed, the bronchial tree should be carefully examined for the presence of occult early lung cancer even when the sputum cytology examination is negative.