Abstract
Recently it has been recognized that environmental factors especially smoking and air pollution have played important roles in the causation of lung cancer, although the histogenesis of lung cancer is still not completely elucidated, it is postulated that squamous cell carcinoma of the lung may arise from the metaplastic mucosa of the bronchi via dysplastic changes. However, evidences supporting this opinion is not adequate on the basis of investigation of the human materials.
Histological examination were performed on the bronchial epithelium of the right lung obtained from the 185 autopsy cases. Morphological changes were classified into six types such as goblet cell hyperplasia, basal cell hyperplasia, transitional metaplasia, squamous metaplasia, atypical metaplasia and minute carcinoma.
Goblet cell hyperplasia had no correlation with aging. Basal cell hyperplasia and metaplastic changes had close interrelationship with aging. Squamous metaplasia was observed in 21% of the cases. Frequently, squamous metaplasia occured at the bifurcation of the bronchi.
There was no correlation between atypical metaplasia and aging. Atypical metaplasia was found in 10 cases (5% of cases). These cases were all male subjects.
These epithelial changes were found more frequently in smokers.
There were three minute carcinomas found in 3 cases (1.6%). Squamous metaplasia was noted around the minute carcinoma in one case. However, remaining two cases had no metaplastic change around the minute carcinomas, which seemed to have arised from the ductal epithelium of the bronchial gland.
These observations support the assumption that squamous cell carcinoma of the lung may not always arise through the squamous metaplasia or atypical metaplasia of bronchial muoosa and direct causation of the carcinoma without any metaplastic changes may be possible in some instances based on this study.
