Recent progress in endocrinology, cytokine research, and oncology has provided new information for further understanding of ectopic hormone-producing tumors. The mechanisms responsible for this morbidity need further investigations to clarify the neuroendocrine nature of tumor cells. Meanwhile, a common hormonal substance produced by a specific tumor could serve as a specific tumor marker for the tumor, as is the case of ProGRP for small cell lung cancer. The development of drugs for ectopic hormonal syndrome might be a good lesson of the molecular targeting for hormone signaling pathways. It is reasonable to postulate that the clinical entities covered by the term 'ectopic humoral syndrome' will be increasing.