Lung Cancer: The Daily PANCE Blueprint

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Lung Cancer: The Daily PANCE Blueprint

A 68-year-old man with a 40-pack-year history has cough, hemoptysis, a 15-pound weight loss, and a central hilar mass; labs show a sodium of 124 mmol/L with concentrated urine. Which paraneoplastic syndrome best explains his hyponatremia?

A. SIADH (ectopic ADH)
B. Humoral hypercalcemia of malignancy (PTHrP)
C. Cushing syndrome (ectopic ACTH)
D. Lambert-Eaton myasthenic syndrome
E. Secondary polycythemia

Answer and topic summary

The answer is A. SIADH (ectopic ADH).

A central or hilar mass in a heavy smoker with euvolemic hyponatremia and inappropriately concentrated urine points to small cell lung cancer producing ectopic antidiuretic hormone (SIADH). Small cell also causes ectopic ACTH (Cushing syndrome) and Lambert-Eaton myasthenic syndrome, but neither explains the low sodium; squamous cell carcinoma classically causes hypercalcemia via PTHrP; and secondary polycythemia is tied to renal cell carcinoma.

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Covered under ⇒ PANCE Blueprint Pulmonary ⇒ Pulmonary Neoplasms ⇒ Lung Cancer

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