A Woman with Headache and Hypertension

Her blood pressure was 207/143 mm Hg and potassium 2.0 mmol/l. Pulmonary edema was present on chest radiograph, and both electrocardiography (EKG) and echocardiography showed left ventricular hypertrophy. The patient had refractory hypokalemia despite potassium supplementation, and blood pressure control was elusive even with maximal doses of lisinopril, losartan, labetalol, and spironolactone. Abdominal imaging showed a small renal mass (see Figure 1). What did pathology of the excised mass show?