Paraneoplastic syndromes
Syndrome	Mechanism	Example
Cushing Syndrome	ACTH-like substance	Lung small cell anaplastic (oat cell) carcinoma
Hypercalcemia	Parathormone-like substance	Lung (squamous cell) carcinoma
Hyponatremia	Inappropriate ADH secretion	Lung small cell anaplastic (oat cell) carcinoma
Polycythemia	Erythropoietin-like substance	Renal cell carcinoma
Trousseau Syndrome	Hypercoagulable state	Various carcinomas
Hypoglycemia	Insulin-like substance	Various carcinomas and sarcomas
Carcinoid Syndrome	5-hydroxy-indoleacetic acid (5-HIAA)	Metastatic malignant carcinoid tumors

A paraneoplastic syndrome occurs when a neoplasm elaborates a substance that results in an effect that is not directly related to growth, invasion, or metastasis of the tumor itself. Most paraneoplastic syndromes result from elaboration of hormone-like substances by the neoplastic cells, but a variety of effects are possible. Sometimes the appearance of the paraneoplastic syndrome may precede diagnosis of the neoplasm and may give a clue to its presence.

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