Cytology Smears of Rapid On-site Evaluation as Supplemental Material 
for Molecular Testing of Non-small Cell Lung Cancer

Abstract

Background and objective The thoracic small biopsy sampling procedure including transbronchial forceps lung biopsy (TBLB) and endobronchial ultrasound transbronchial needle aspiration (EBUS-TBNA) can be accompanied by rapid on-site evaluation (ROSE) of sample material to provide immediate feedback for the proceduralist. The present study aims to investigate the supplemental effect of ROSE smear samples for lung cancer molecular test. Methods In a retrospective study, 308 patients admitted to our hospital from August 2020 to December 2022 undergoing diagnostic TBLB and EBUS-TBNA with ROSE and subsequently diagnosed as non-small cell lung cancer (NSCLC) were analyzed. The matched formalin-fixed paraffin-embedding (FFPE) tissue section and ROSE smears for tumor cellularity were compared. DNA yields of smears were determined. Real-time polymerase chain reaction (PCR) and next-generation sequencing (NGS) were performed on adequate smear samples. Results ROSE smear samples were enriched in tumor cells. Among 308 biopsy samples, 78 cases (25.3%) exhibited inadequate FFPE tissue sections, whereas 44 cases (14.3%) yielded adequate smear samples. Somatic mutations detected in the FFPE tissue section samples were also detected in the matching adequate smear sample. Conclusion ROSE smear samples of the thoracic small biopsies are beneficial supplemental materials for ancillary testing of lung cancer. Combined use of cytology smear samples with traditional FFPE section samples can enhance the detection rate of informative mutations in patients with advanced NSCLC. We recommend that the laboratory could further evaluate the ROSE cell smears of the patient when FFPE tissue sections are inadequate, and that adequate cell smears can be used as a supplemental source for the molecular testing of NSCLC.

Keywords

• lung neoplasms
• biopsy
• rapid on-site evaluation
• molecular testing