Low mutational rate of K-ras codon 12 in singular bronchoscopy specimens in suspected lung cancer

Mutations of the K-ras gene are found in a subset of non-small- cell lung carcinomas (NSCLC). The aim of our study was to determine the K-ras codon 12 mutation in the first, singular bronchoscopy specimen in parallel with the cytological examination for the diagnosis of lung cancer. Samples were obtained by diagnostic bronchoscopy in 140 patients with suspected lung tumors. The analysis of K-ras mutations was carried out by a sensitive two-step mutation- enriched polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. This method has been confirmed earlier to be positive for mutated tumor cells and negative for normal lung parenchyma and bronchus. Of the 140 patients with suspected cancer, 93 were diagnosed as NSCLC by cytology or histology in either the same specimen used for the detection of K-ras mutation or in later biopsies. However, only four K-ras codon 12 mutations were detected in the first bronchoscopic material: one in adenocarcinoma, two in squamous cell tumors, and one mutation was found in a patient with dysplasia which was diagnosed later as a squamous cell carcinoma. Our findings indicate that although the K-ras (codon 12) mutation is a gene lesion infrequently detectable in a singular specimen taken at the first bronchoscopy examination in cases of clinically suspected lung cancer, the detection of this mutation can help to confirm the cytological diagnosis of NSCLC or may be even diagnostic in cytologically negative cases.