However, ambiguity exists as one of the studies on SCLC involving immunohistochemistry (IHC) and RNA-sequencing analysis revealed that TAMs also express the IC protein PD-L1 (i.e., PD-L1+ TAMs) [86], which attenuates the phagocytosis of SCLC cells through its interaction with its cognate receptor PD-1 expressed on immune cells, such as T cells. This evidence concerns the gene PDCD1 and small cell lung carcinoma.