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"Paraneoplastic" refers to features of a cancer considered to be due to its remote effects (eg, aberrant production of hormones, peptides, cytokines) that cannot be attributed either to its direct invasive or its metastatic properties
Small cell lung cancer is most common tumor association
Can occur despite relatively limited neoplastic growth
May provide an early clue to presence of certain types of cancer
Course usually parallels that of the primary cancer
Effective cancer treatment should be accompanied by resolution of the paraneoplastic syndrome
Conversely, recurrence of the cancer is sometimes heralded by return of syndrome
Metabolic or toxic effects of the syndrome (eg, hypercalcemia, hyponatremia) may be a more urgent hazard to life than the underlying cancer
Many of the neuromuscular, dermatologic, and rheumatologic paraneoplastic syndromes are caused by antibodies directed against tumor antigens that share epitopes with normal tissue; testing for antibodies can often detect syndrome-specific antibodies
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Hypercalcemia, hyponatremia
Clinical manifestations of cancer are usually due to
Pressure effects of local tumor growth
Infiltration or metastatic deposition of tumor cells in a variety of organs in the body
Certain systemic symptoms
Patients with advanced or widespread metastatic cancer may have anorexia, malaise, weight loss, and sometimes fever
Systemic symptoms of cancer are usually not specific (except in the case of functioning tumors)
In the paraneoplastic syndromes, clinical findings may resemble those of primary endocrine, dermatologic, rheumatologic, hematologic, or neuromuscular disorders
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