ROS1 and neoplasm: In the TBNA cohort, an insufficient number of tumour cells led to limited biomarker testing for PD-L1 by immunohistochemical (IHC) staining and sequential testing for EGFR mutation by real-time polymerase chain reaction (RT-PCR), ALK rearrangement by IHC staining and ROS1 fusion by fluorescent in situ hybridisation (FISH)) in nine patients (21.43%).