EGFR/K-ras mutations in lung adenocarcinoma and atypical adenomatous hyperplasia (AAH)

21074 Background: Mutations in the epidermal growth factor receptor (EGFR) gene and k-ras gene are found in 10–30% of non-small cell lung cancer, and are useful to predict the efficacy of EGFR-tyrosine kinase inhibitors. Such mutations are also onco- developmentally important especially in lung adenocarcinoma, but the exact incidences of such mutations in adenocarcinoma/AAH and surrounding normal lung. Methods: A total of 45 consecutive patients with lung adenocarcinoma and/or AAH (18 females; mean age, 65 years) who received thoracotomy from August 2005 through December 2006. In each case, EGFR/k-ras mutations were examined in specimens cut from adenocarcinoma/AAH and normal lung; in the present study, pure bronchioalveolar carcinoma (BAC) was reviewed separately from adenocarcinoma. Results: As 12 (27%) of all 45 patients had multiple adenocarcinoma/BAC/AAH lesions, mutations were examined in 59 lesions (41 adenocarcinomas, 7 BACs, 11 AAHs) and 45 normal lung tissues. EGFR and k-ras mutations were documented in 37% (15/41) and 2% (1/41) of adenocarcinomas, and no EGFR/k-ras mutation was documented in any BAC, AAH, or normal lung tissue. Next, clinical characteristics of patients were compared between patients with solitary adenocarcionma/BAC/AAH lesion and those with multiple lesions; non-smoker were more frequently documented in multiple-lesions group (42%) than in solitary-lesion group (15%), and there was no significant difference in other characteristics such as sex and age. Conclusions: EGFR mutation was not documented in non-invasive (BAC) or pre-neoplastic (AAH) lesion in this series, which may suggest that EGFR mutation play a critical role in the development of invasive adenocarcinoma. No significant financial relationships to disclose.