Fine structure of adrenal cortex in ectopic ACTH syndrome.

A 49-year-old man with pancreatic adenocarcinoma, suggestive of islet cell origin, showed clinical and biochemical features of ectopic ACTH syndrome and underwent bilateral adrenalectomy. Light microscopy revealed adrenocortical compact cell hyperplasia and lipid depletion. The zona glomerulosa was detected in small foci and fasciculata cells extended up to the capsule. Electron microscopy disclosed enlargement of adrenocortical cells, massive SER accumulation, RER increase, lipid depletion, prominence of the Golgi apparatus and development of complex interdigitations between closely apposed cell membranes. These changes were attributed to the stimulative effect of ACTH discharged from the non-pituitary tumor. Mitochondria exhibited enlargement, pleomorphism and cavitation. Most of the adrenocortical cells contained mitochondria with vesicular cristae--a characteristic feature of fasciculata cells. In a few cells, under the capsule, some mitochondria possessed lamellar cristae. Gradual transformation to the vesicular type was, however, apparent indicating that mitochondria are not rigidly constant structures.