CXCR4 and neoplasm: A study conducted by Rösner et al. revealed that PD-L1 expression in lung NENS is positively correlated with tumor grade, a higher Ki-67 index, and enhanced CXCR4 expression, while displaying an inverse association with somatostatin receptor 1 and chromogranin, suggesting that PD-L1 expression is not only prevalent in lung NENs but also escalates with tumor malignancy and might be linked to poorer patient outcomes [39].