Erythropoietin receptor messenger ribonucleic acid (mRNA) and/or protein has been identified in a wide range of cancers, leading to the speculation that tumor progression may be a consequence of activation of endogenous erythropoietin receptors by exogenous erythropoiesis-stimulating agents, thereby promoting tumor cell proliferation and angiogenesis and inhibiting apoptosis. This evidence concerns the gene EPOR and neoplasm.