Circulating tumour cells(CTCs)were enriched in the peripheral blood of four patients with Stage I non-small cell lung cancer(NSCLC).Octamer-binding transcription factor-4 positive(OCT4+)and negative(OCT4-)CTCs were identified and captured by interphase fluorescence in situ hybridisation(iFISH).Single cell whole exome sequencing(WES)was performed and the corresponding bioinformatics data were analysed.OCT4+cells were successfully detected in peripheral blood collected from all four Stage I lung cancer patients.Moreover,the tumour mutational burden(TMB)values observed for OCT4+samples from the same patients were slightly smaller than those of the OCT4-samples;the difference was not statistically significant(P ＞ 0.05).Thirteen and six characteristic mutations were found in negative samples and positive samples,respectively.The findings indicate that this methodology provides a potential diagnostic index for the early detection of NSCLC.