Atypical adenomatous hyperplasia of the lung

Clinicomorphological analysis was performed in 12 cases of atypical adenomatous hyperplasia of the lung (AAH). This is the proliferative lesion consisting of atypical epithelial cells along the alveolar septa which are found incidentally during pathologic examination of the lung resected because of cancer. We studied morphological and biological characteristics of AAH cells including cytodifferentiation, proliferative activity, tumor-suppressor genes. Our review of the studies of AAH revealed that AAH is alveolar intraepithelial dysplasia and a precursor of lung adenocarcinoma. AAH is an important lesion corresponding to a step in carcinogenesis for peripheral lung adenocarcinomas.