A 34-year-old man is referred for evaluation of hypeension and persistent hypokalemia in spite of taking oral potassium supplements. Blood pressure is 180/110 mm Hg. Serum sodium is 149 mEq/L (normal 140 to 148 mEq/L); potassium, 3.3 mEq/L (normal 3.6 to 5.2 mEq/L); Bicarbonate, 29 mEq/L (normal 22 to 29 mEq/L); Chloride, 103 mEq/L (normal 98 to 107 mEq/L); and Urea nitrogen, 23 mg/dL (normal 7 to 18 mg/ dL). Computed tomography demonstrates a 3-cm mass in the right adrenal gland. The most likely diagnosis is