A 65-year-old man presents to the emergency department with worsening shortness of breath and cough over the past 2 months. He has also had a 15-lb weight gain over the same period. He has smoked 2 packs of cigarettes daily for the past 30 years. His physical examination is remarkable for an obese man with bilateral supraclavicular fullness and a blood pressure of 200/120 mm Hg. Imaging studies reveal a 5-cm left hilar mass with an enlarged subcarinal lymph node. His laboratory studies show normal complete blood count (CBC) and comprehensive metabolic panel (CMP) except for a serum sodium concentration of 150 mEq/L (reference range: 136–142 mEq/L), serum potassium of 2.9 mEq/L (reference range: 3.5–5.0 mEq/L), and serum bicarbonate of 32 mEq/L (reference range: 21–28 mEq/L). He is admitted to the hospital for further workup. Bronchoscopy with endobronchial ultrasound for transbronchial biopsy of the left hilar mass and subcarinal lymph node is performed. The preliminary result of the biopsy is consistent with malignancy.