[Occult lung cancer with positive cytology and normal chest film--an analysis of 54 cases].

From 1973 to 1980 and 1982 to 1984, mass annual screening was carried out in Yunnan Tin Corporation. Chest X-ray and sputum cytology were used to detect lung cancer among subjects with an underground work history over 10 years and over 40 years of age. 54 cases of occult lung cancer with positive cytology and negative X-ray plain film were found, 48 out of 100,725 subjects and 6 out ot 8,808 out-patients. 42 lesions were located by bronchoscopy and 12 by various roentgenologic examinations. Among these 54 cases, 52 (96.3%) were central type lung cancers. Squamous cell carcinoma was found in 53 and small cell anaplastic carcinoma in only 1. Diagnosis was established by pathology in 35 and by cytology in 19. In 18 cases treated by surgery, there were 15 Ia stage and 3 Ib (UICC staging system). 3 Ib died of recurrence 33, 62 and 101 months after operation. 1 Ia died of residual cancer recurrence 21 months after sleeve-resection. The overall 5 year survival rate was 91.6% (11/12). The authors believe that X-ray plain films sometimes fail to detect the early stage central type lung cancers. Bronchoscopy, in particular fiberoptic bronchoscopy is one of the most effective means in diagnosis and location. By bronchoscopy, in general, the tumor could be detected and the extent of involvement in the bronchus assessed. Finally, the authors emphasize that mass screening is a useful method to detect early lung cancer among the high risk population.