Extent of bronchioloalveolar pattern and expression of the epidermal growth factor receptor in surgically resected lung adenocarcinomas

Abstract

20065 Background: An increasing number of studies are exploring relations between the bronchioloalveolar differentiation of adenocarcinomas and clinical, radiological and molecular parameters. We investigated the potential relation between the extent of the bronchioloalveolar carcinoma (BAC) component of adenocarcinomas and the expression of the epidermal growth factor receptor (EGFR) protein. Methods: We retrospectively reviewed data from all patients who underwent surgery for lung cancer in our hospital between February 1, 2001 and May 31, 2005 (n = 366), and in whom pathologic analysis had revealed an adenocarcinoma histologic subtype. Paraffin embedded tissue samples were retrieved and re-examined. Samples exhibiting either a pure BAC histology or a mixed adenocarcinoma histology with a >50% BAC component (n = 46) were selected for EGFR expression analysis by immunohistochemical staining. Patient demographics, stage and tumor differentiation data were recorded. Histological analysis was carried out using the WHO 1999/2004 criteria for lung cancers. For EGFR expression evaluation, samples were assigned a score ranging from 0 to +3. Expression was considered positive when the score was +1 or higher. Statistical analysis was performed using the chi-square test. Results: Of the 46 tumor samples examined, 10 had a BAC component of 50–79% (group A), 18 had BAC component of 80–99% (group B) and 18 exhibited a pure BAC histology (group C). Male/female ratio was 61.3%/38.7%. Mean age at presentation was 61.6 years. Among group A, 4 patients were EGFR positive and 6 were EGFR negative. 16 group B patients were EGFR positive and 2 were EGFR negative. Similarly, 16 group C patients were EGFR positive and 2 were EGFR negative. This distribution suggests that EGFR is more often expressed with increasing BAC component (p = 0.0041). No correlation was observed between demographics and EGFR expression or the extent of BAC pattern. Conclusions: EGFR expression is related to the extent of the BAC component in adenocarcinomas, with statistical significance. Study of a larger number of patients and correlation of this finding with EGFR and Ras mutational status and responsiveness to therapy are warranted. No significant financial relationships to disclose.