Which statement is true about small cell lung cancer?

• A. It has the lowest metastatic risk
• B. It is associated with SIADH
• C. It is most common in non-smokers
• D. It is always central

Answer: (B)

Small cell lung cancer is a highly malignant neuroendocrine tumor strongly linked to smoking, with rapid growth and early widespread metastasis. A defining paraneoplastic feature is SIADH, caused by ectopic production of antidiuretic hormone by the tumor. This leads to dilutional hyponatremia and inappropriately concentrated urine, which is a classic clue in patients with this cancer type.

Why this statement fits best: SIADH from ectopic ADH production is a hallmark association with small cell lung cancer, making hyponatremia a common presenting or incidental finding in these patients. In contrast, the other statements don’t align with the typical behavior of SCLC: it does not have the lowest metastatic risk (it spreads early and aggressively); it is not most common in non-smokers (it is almost exclusively seen in smokers); and while it is often central, it is not always central, as occasional peripheral occurrences can happen.