Cancer that forms in the tissues of the adrenal glands (two glands located just above the kidneys). The adrenal glands make hormones that control heart rate, blood pressure, and other important body functions. Adrenal cancer that starts in the outside layer of the adrenal gland is called adrenocortical carcinoma. Adrenal cancer that starts in the center of the adrenal gland is called malignant pheochromocytoma.