Alveolar atypical hyperplasia in association with primary pulmonary adenocarcinoma: a clinicopathological study of 10 cases.

BACKGROUND A distinctive cytologically atypical lesion has been found in patients with primary adenocarcinoma of the lung. The aim of this study was to characterise the lesion and assess its role in tumour pathogenesis. METHODS Lung parenchyma from 175 consecutive resection specimens for primary pulmonary adenocarcinoma were examined. Foci of atypical hyperplasia were identified. Cell proliferation state and expression of S100 and carcinoembryonic antigens were evaluated by immunohistochemistry. Clinical data on cigarette smoking and occupational exposure to carcinogens were abstracted from inpatient case notes. RESULTS Ten cases (5.7%) with these distinctive cytologically atypical lesions were identified. The lesions showed immunohistochemical evidence of increased cell proliferation and focal carcinoembryonic antigen expression. The associated adenocarcinomas were of peripheral (parenchymal) type. There was an association with cigarette smoking and two of the 10 patients had synchronous carcinomas elsewhere in the lung. CONCLUSION The clinical and pathological associations of these lesions suggest that they may be important in the histogenesis of primary pulmonary adenocarcinoma.