[Etiology of ectopic hormone producing tumors].

Inappropriate secretion of peptide hormones and other associated proteins by tumors is the most common cause of paraneoplastic syndromes. Sensitive assay techniques have permitted detection of polypeptide hormone secretion by tumors even in the absence of clinically overt syndromes. Moreover, it has been demonstrated that most or all nonendocrine tissues produce small amounts of a variety of peptide hormones and hormone precursors. Nevertheless, the term ectopic hormone syndromes occurring with nonendocrine neoplasms is well established and widely used. We summarize etiology of 'classic' ectopic hormone producing tumors to help establish the diagnosis of paraneoplastic humoral syndromes.