CXCR4 and neoplasm: Correlations with different markers for neuroendocrine tumours revealed a positive relationship between FAM159B and NSE (but not with chromogranin A), as well as with various receptors and membrane proteins commonly expressed in these tumours (but also in others), associated either with good prognosis, such as the D2 dopamine receptor and the different somatostatin receptors or with a negative prognosis, such as the chemokine receptor CXCR4 and PD-L1 [7,9].