Pain syndromes in the cancer patient.

Paraneoplastic syndromes affect the nervous system in a very small percentage of patients with cancer. In those patients, portions of the nervous system are damaged or destroyed, usually in association with a small and often occult neoplasm elsewhere in the body. Current evidence suggests that these syndromes occur when the body mounts an immune response to an antigen shared between the tumor and the nervous system. The immune attack is then misdirected against that portion of the nervous system that possesses the "onconeural" antigen.