In line with these observations, Cheng et al.180 found that in GC patients with PD-L1-negative tumor tissue, the imaging flow cytometry signal analysis of isolated CTC was as varied as that of IHC staining, suggesting that the expression of CTC PD-L1 was useful in the immunophenotypic differential diagnosis of tumors and could be a potential candidate for anti-PD-1/PD-L1 immune checkpoint therapy 143. Here, PDCD1 is linked to neoplasm.