Histopathological Study of Adenocarcinoma and Hyperplastic Epithelial Lesion of the Lung

To clarify the histogenesis of lung adenocarcinoma, multiple specimens including lung tumor and non-neoplastic lung tissues were examined histologically and immunohistochemically in 131 surgically resected lung cancer cases. Six new small or minute adenocarcinomas were incidentally found in adenocarcinoma cases. Adenomatous hyperplasia (AH) and atypical adenomatous hyperplasia (AAH) existed in 29 cases (22.1%) and 16 cases (12.2%), respectively. In 65 cases of adenocarcinoma, AH and AAH were present in 22 cases (34.4%) and 12 cases (18.8%), respectively. In adenocarcinoma cases, AH and AAH were more frequent and occured more multiply than in squamous cell carcinoma cases. In 11 cases of multiple primary lung cancer, both AH and AAH occured more frequently (72.2%) than in solitary lung cancer cases. There were 6 cases in which foci of adenocarcinoma and AAH coexisted. Immunohistochemically, surfactant apoprotein-positive cells were present focally or diffusely in cases of adenocarcinoma, AAH and AH. Therefore, it is suggested that some adenocarcinomas might originate from AAH.