For the most part, it is evident in the literature that positive expression of PD-L1 occurs more frequently on tumour-infiltrating immune cells within the SCLC, compared to PD-L1 expression on tumour cells, and high PD-L1 expression on the infiltrating immune cells has been associated with favourable clinical outcome in SCLC patients [28,51,52,53]. Here, CD274 is linked to small cell lung carcinoma.