CXCR4 and neoplasm: Well-known examples are well-differentiated G1 or G2 gastroenteropancreatic neuroendocrine tumours that overexpress somatostatin receptors (SSTs) [9, 10] and aggressive tumours such as small-cell lung cancer, lymphomas, or G3 gastroenteropancreatic neuroendocrine tumours that overexpress the chemokine receptor CXCR4 [9–12].