Interrelationships were also analysed between GPER expression and the expression of several typical neuroendocrine tumour markers, including chromogranin A (CgA), programmed death-ligand 1 (PD-L1), the chemokine receptor CXCR4, and the somatostatin receptors (SST) 1–5, which were determined on the same set of samples as part of previous studies [28,30,31]. This evidence concerns the gene GPER1 and neuroendocrine neoplasm.