Disproportionate representation of KRAS gene mutation in atypical adenomatous hyperplasia, but even distribution of EGFR gene mutation from preinvasive to invasive adenocarcinomas

• Published in: The Journal of pathology 2007-07, Vol.212 (3), p.287-294
• Main Authors: Sakamoto, H, Shimizu, J, Horio, Y, Ueda, R, Takahashi, T, Mitsudomi, T, Yatabe, Y
• Format: Article
• Language: English
• Subjects: Adenocarcinoma - genetics; atypical adenomatous hyperplasia; Biological and medical sciences; Disease Progression; DNA Mutational Analysis; EGFR; Humans; Hyperplasia - genetics; Investigative techniques, diagnostic techniques (general aspects); KRAS; lung; Lung Neoplasms - genetics; Medical sciences; Mutation; Neoplasms, Multiple Primary - genetics; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Precancerous Conditions - genetics; preinvasive lesion; Proto-Oncogene Proteins - genetics; Proto-Oncogene Proteins p21(ras); ras Proteins - genetics; Receptor, Epidermal Growth Factor - genetics; Smoking - genetics
• ISSN: 0022-3417; 1096-9896
• DOI: 10.1002/path.2165

In the resected lung, additional small lesions are occasionally found incidentally, and include the full spectrum of preinvasive to invasive lesions under the current putative schema of the sequential development of lung cancer. In this study, we examined EGFR and KRAS gene mutations in 119 synchronous pulmonary lesions, including 40 precursor lesions (atypical adenomatous hyperplasia, AAH), 26 carcinomas in situ (non‐mucinous bronchioloalveolar carcinoma, BAC), 14 minimally invasive adenocarcinomas, 34 overt invasive adenocarcinomas, and five of other subtypes of cancer. Although the mutually exclusive nature of KRAS and EGFR gene mutations was maintained even in preinvasive lesions, the incidences of the lesions along the putative progression schema were quite different. The KRAS gene was mutated in 33% of AAH, 12% of carcinomas in situ, 8% of minimally invasive adenocarcinomas and 0% of well‐differentiated adenocarcinomas, whereas the frequencies of EGFR mutation did not fluctuate greatly, at 25%, 51%, 36%, 86% and 67%, respectively. These results are consistent with the findings of a published gene‐targeted mouse model; the mice expressing oncogenic KRAS developed AAH but not invasive adenocarcinoma, whereas a spectrum of preinvasive to invasive adenocarcinomas was observed in the mice expressing mutant EGFR. Taking these factors together, it is suggested that AAH could develop by either KRAS or EGFR gene mutation, but AAH harbouring a KRAS gene mutation might not progress further to an invasive cancer. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.