Progression of a Nelson's adenoma to pituitary carcinoma; a case report and review of the literature.

A 25-year-old woman developed Nelson's syndrome, 3 years after successful bilateral adrenalectomy for Cushing's disease. Despite pituitary surgery and radiotherapy the tumour showed invasive growth, leading to visual disturbance, paresis of the oculomotor nerve and, 34 years after adrenalectomy, to death by widespread purulent leptomeningitis. Autopsy revealed a large adenohypophyseal carcinoma with a metastasis attached to the dura, both tumours showing immunocytochemical staining for ACTH and TSH. We review the literature on metastatic adenohypophyseal carcinoma in Cushing's disease and Nelson's syndrome and discuss the role of proliferation markers as indicators of malignant progression.