Secretion of ACTH by non-pituitary neoplasms is recognized with increasing frequency. While the clinical and biochemical changes associated with ectopic ACTH production have been extensively studied recently, relatively little attention was focused on the morphology of the adrenal cortex and, to our knowledge, the fine structure of the adrenocortical cells in cases of ectopic ACTH syndrome has not been described so far. We report here the electron microscopic findings in the adrenal cortex of a 50-year-old man with a pancreatic apudoma. The patient showed the characteristic clinical and biochemical features of ectopic ACTH syndrome and because of extensive hypercorticism, underwent bilateral adrenalectomy.By light microscopy, the adrenal cortices showed extensive compact cell hyperplasia and lipid depletion. The zona glomerulosa was present in small foci and, except for a few places, fasciculata cells were noted under the fibrous capsule.
