Role of molecular and cellular techniques applied to EBUS-TBNA of mediastinal lymph nodes for lung cancer staging

Introduction: Accurate NSCLC staging is of major importance since it dictates the choice of treatment and prognosis. EBUS-TBNA is a minimally invasive method to sample mediastinal lymph nodes. The concomitant identification of cancer biomarkers is important to improve EBUS-TBNA staging. Aim: Assess the feasibility and role of EBUS-TBNA combined to the identification of tumour-associated antigens and tumour-associated immune responses to diagnose lymph node metastases and pathological characteristics in lymph node aspirates. Methods: In a prospective study, EBUS-TBNA samples from 57 patients with confirmed or suspected lung cancer were analysed by cytopathology, flow cytometry (FACS) and reverse-transcriptase polymerase chain reaction (RT-PCR). Results: All samples were adequately processed by the 3 different techniques. Among the 47 samples diagnosed with tumour cell by cytopathology, 70% showed the presence of cytokeratin-19 (CK-19) cells by FACS and 83% of the SCLC were CK-19 negative. CK-19 phenotype and gene expression were significantly correlated (r= 0.901) and cells with this phenotype also expressed CEA, sialyl Lewis X and CD44+ in 22.2%, 25.0% and 18.7% of cases. The expression of the EPCAM gene was significantly higher in the cytopathologically diagnosed cases (p=0.03). The analysis of immune cells profile in the aspirates of these patients revealed a decrease in total leukocytes (p=0.022) and a increase in monocytes (p= 0.039). Conclusions: The combination of molecular and cellular biology techniques with EBUS-TBNA might be a feasible option to improve NSCLC staging and offer an individualized diagnostic and therapeutic approach to lung cancer patients.