Introduction: Molecular testing for epidermal growth factor receptor (EGFR) and KRAS mutations is of increasing clinical importance in daily practice. In this study, we aimed to investigate the yield and applicability of molecular testing for KRAS and EGFR mutations in cytologic specimens obtained by EUS or endobronchial ultrasound (EBUS)-guided fine needle aspiration (FNA).
Methods: We selected all patients with an EUS- or EBUS-guided FNA positive for lung adenocarcinoma from the database of our tertiary care center for endosonography. Direct smears were Giemsa and Papanicolaou stained. The remaining material was processed in cell blocks. Both cell blocks and smears were considered suitable for molecular analysis when >40% of the aspirated cells were tumor cells. All eligible samples were investigated for KRAS and EGFR mutations by polymerase chain reaction followed by direct sequencing.
Results: Four hundred sixty-two patients underwent EUS or EBUS-FNA using 22-gauge needles. In 35 patients, FNA showed lung adenocarcinoma. In eight patients, molecular analysis could not be performed because of insufficient material after routine and immunocytochemistry (n = 3), a low percentage (<40%) of tumor cells (n = 3), or an insufficient DNA quality (n = 2). The average percentage of tumor cells was 73% ± 23%. Molecular analysis could reliably be performed in 27 patients (77%). Mutation analysis showed KRAS and EGFR mutations in tumor samples from 10 (37%) and two (7%) patients, respectively. In one patient, two EGFR mutations (p.Thr790Met and p.Leu858Arg) were detected.
Conclusions: Molecular analysis for KRAS and EGFR mutations can be performed routinely in cytologic specimens from EUS- and EBUS-guided FNA.