RESUMEN
The Paraneoplastic syndromes include the disorders that accompany benign or malignant tumors but are not directly related to mass effects or invasion by the primary tumor or its metastases. Neoplastic cells can produce a variety of peptides that exert biologic actions at local and distant sites and can elicit responses that cause a variety of hormonal, hematologic, dermatologic and neurologic symptoms. Almost every type of malignancy has the potential to produce hormones or cytokines or to induce immunologic responses. Lung cancers, both non-small cell and small cell, are capable of producing a variety of paraneoplastic syndromes. The majority of such syndromes are caused by small cell carcinomas, including many endocrinopathies. Syndrome of inappropriate antidiuretic hormone (SIADH) has been commonly associated with small cell carcinoma and is often seen in these patients. However, SIADH associated with squamous cell carcinoma has rarely been reported on, and the mechanism for this rare association is still unknown. We present here a case of a 77-yr-old man who developed SIADH caused by squamous cell carcinoma of the nasopharynx.