CMTM6 and small cell lung carcinoma: SCLC carries the genetic mutation profile including ProGRP, NCAM, PGP9.5, and gastrin etc. Therefore, the different cell origin of NSCLC and SCLC, the individual genetic mutation profile, together with the different microenvironment may cause the higher expression of CMTM6/PD-L1 in NSCLC.