Assessment of EGFR and K-ras mutations in fixed and fresh specimens from transesophageal ultrasound-guided fine needle aspiration in non-small cell lung cancer patients

In non-small cell lung cancer (NSCLC) patients, somatic EGFR and K-ras mutations predict therapeutic effectiveness and resistance, respectively, to EGFR tyrosine kinase inhibitors (TKIs). Transesophageal ultrasound-guided fine needle aspiration (EUS-FNA) is a validated technique for diagnosis and staging of NSCLC. In the present study, we compared the feasibility and reliability of EGFR and K-ras gene mutation analysis in fixed and fresh mediastinal lymph nodes and extra-lymph nodal samples obtained by EUS-FNA in patients suspicious for NSCLC. Thirty-six patients were enrolled into the study. For each patient, DNA was extracted from both fresh samples and fixed cytological smears. Exons 18-21 of EGFR and exon 2 of K-ras were amplified by PCR and mutation status was determined by direct sequencing and pyrosequencing. All cases were eligible for analysis. NSCLC was diagnosed in 32 patients (25 adenocarcinomas and 7 squamous cell carcinomas) and 4 patients were free of malignancy. Of the 25 patients with adenocarcinoma, EGFR mutations were detected in 2 (8%) fresh tumor samples and in 3 (12%) fixed cytological smears. K-ras mutations were detected in 8 (32%) fresh samples, and in 9 (36%) fixed cytological smears. Fixed and stained cytological samples seem to be more reliable than fresh material for molecular analysis.