Paraneoplastic syndrome: A group of signs and symptoms caused by a substance that is produced by a tumor or in reaction to a tumor. Paraneoplastic syndrome can be due to a number of causes, including hormones or other biologically active products made by the tumor, blockade of the effect of a normal hormone, autoimmunity, immune-complex production, and immunosuppression. By definition, paraneoplastic syndrome is not produced by the primary tumor itself or by its metastases, nor is it caused by compression, infection, nutritional deficiency, or treatment of the tumor.
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Last Editorial Review: 5/13/2016