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Vol.41 No.6 contents | Japanese/English |
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- Original Article -
Influence of Lesion Location on Detection of Lung Adenocarcinoma and Peripheral Squamous Cell Carcinoma
Haruo Sasaki, Yoshiaki Taoka and Kunihiko HaradaGeneral Medical Checkup Center of Tokushima Prefecture
Objective: In order to evaluate the influence of normal chest structures on radiologic detection of lung cancers, we examined the location of lesions detected by screening. Methods: The study comprised 132 cases (135 lesions) of lung cancer. They were detected by miniature chest X-ray films taken at annual screenings between April 1991 and March 1999, and consisted of 98 adenocarcinomas and 37 peripheral squamous cell carcinomas. They were separated into groups by stage, tumor size and histological type. The location of the lesions was plotted on a schematic representation of the posteroanterior (PA) view, and their distribution patterns were compared among groups. The areas where early detection of lung cancer was difficult, and the areas where it was easy, as well as the areas of intermediate difficulty were represented on the schematic PA view. The borders around difficult areas were drawn with reference to the distribution pattern of lesions more than 3 cm in diameter, while those around easy areas were based on the distribution pattern of stage I lesions 2 cm or less in diameter. The remaining areas were designated as intermediate areas. The proportion of stage I lung cancers and other indices for three areas were estimated in order to determine differences among them. The distribution pattern of adenocarcinomas was compared with that of squamous cell carcinomas. Previously missed lung cancers among the 135 lesions were identified retrospectively from serial X-ray films. Potentially detectable nodules on previous chest X-ray films were classified as missed lung cancers. The distribution pattern of missed lung cancers is also shown. Results: Most of the stage IA lung cancers were detected in the area where no large normal structures were superimposed on the nodules. Stage III and stage IV lung cancers showed a wider distribution, and the superimposition of normal structures such as the heart, great vessels, pulmonary peripheral vessels, diaphragm, ribs surrounding the apex, clavicle and the tip of the first rib on a considerable number of nodules. There were statistically significant differences among the three areas in the proportion of lesions 2 cm or less in diameter. The proportions of stage I lung cancers within the difficult, intermediate, and easy areas were 34%, 57% and 75% respectively. The ratio of squamous cell carcinomas to adenocarcinomas within difficult areas was higher than that outside them. There was no statistically significant difference in the proportion of missed lung cancers among the three areas. "Areas where lung cancer lesions were often missed" and "areas where early lung cancers could hardly be detected" showed different appearances. Conclusion: The superimposition of normal chest structures markedly influenced the stage and size of adenocarcinoma and peripheral squamous cell carcinoma as detected by chest X-ray. Gross classification of lung fields was made in relation to the efficiency of radiologic detection of early lung cancer.
key words: Lung cancer, Screening, Miniature chest X-ray, Lesion location, Blind area
Received: June 16, 2000
Accepted: September 14, 2001
JJLC 41 (6): 653-660, 2001
