Reliability of Direct Sequencing of EGFR: Comparison between Cytological and Histological Samples from the Same Patient

The results of a recent study have shown the superiority of treatment with gefitinib or erlotinib in lung tumors positive for epidermal growth factor receptor (EGFR) mutation. As a consequence, the complete diagnosis of lung cancer cannot be limited to histotype classification, but should include a series of molecular biology analyses. In most cases, the diagnosis of lung cancer is performed on cytological specimens; therefore, there is a need to obtain a complete and reliable molecular diagnosis on cytologic specimens. Brushing, transbronchial needle aspiration (TBNA) and broncho alveolar lavage during fibro-bronchoscopy allow the sampling of the lung and the mediastinal lymph node. The aim of this study was to demonstrate that direct sequencing of exons 19 and 21 of EGFR in lung tumors, carried out on the cytological samples obtained through fibro-bronchoscopy, is as reliable as the same analysis carried out on a histological surgical sample obtained from the same individual. We considered 50 patients with a histological diagnosis of lung adenocarcinoma whose cytological samples, obtained by fibro-bronchoscopy and histological samples, obtained by surgical resection were available. A comparison of the sensitivity and reliability of the molecular biology analyses carried out on histological and cytological samples of the same patient was carried out. The combined mutation percentage of exons 19 and 21 of EGFR was 10%. The results of the analyses carried out on cytological samples matched those obtained from the histological samples. The feasibility of EGFR analysis on cytological samples has already been demonstrated in previous studies, however these studies referred to the method of fluorescence in situ hybridization, or did not perform any comparison between histological samples from the same patient; our work, on the other hand, shows that direct sequencing of exons 19 and 21 of the EGER gene is feasible on fibro-bronchoscopy cytological samples with the same reliability offered by the histological samples obtained from the same patient.