Question: What is the difference between Nelson's syndrome and a recurrence of a pituitary tumor?
 
Answer: Nelson's syndrome is a development of a pituitary tumor following bilateral adrenalectomy in patients with Cushing's disease. In other words, Nelson syndrome can only occur in patients who have both adrenal glands removed. If the adrenal glands have not been removed, and the patient still has a pituitary tumor or Cushing's syndrome, this represents a recurrence of the pituitary tumor and not Nelson's syndrome.