High concordance of EGFR mutation status between histologic and corresponding cytologic specimens of lung adenocarcinomas

BACKGROUND Activating mutations in the epidermal growth factor receptor (EGFR) in non-small cell lung carcinoma (NSCLC) are associated significantly with responsiveness to EGFR tyrosine kinase inhibitors. The objective of this study was to investigate the suitability of cytologic specimens for assessing EGFR mutations in lung adenocarcinomas. METHODS Sixty paired histologic and cytologic specimens of lung adenocarcinoma were collected. Exons 18 through 21 of the EGFR gene were amplified using polymerase chain reaction, and the mutation status of each sample was analyzed by pyrosequencing. A comparison of EGFR mutation status between histologic specimens and cytologic specimens was performed. RESULTS The overall EGFR mutation concordance rate between histologic specimens and corresponding cytologic specimens was 91.7%. No significant difference was observed in the concordance rate between cytologic specimens from primary lesions and specimens from metastatic lesions (P = .63). The following parameters were correlated with the most reliable EGFR mutation results using the pyrosequencing method (100% concordance with the corresponding histologic specimens) in cytologic samples: a DNA concentration >25 ng/L, content of >30 tumor cells, or a tumor percentage >30%. CONCLUSIONS In this study, routinely prepared cytologic specimens were reliable sources for assessing EGFR mutation status. The authors concluded that cytologic specimens from metastatic lesions and primary tumors are suitable for the successful assessment of EGFR mutation status. Cancer (Cancer Cytopathol) 2013;121:311-9. (c) 2012 American Cancer Society.