Fine structure of adrenal adenomata causing Cushing's syndrome.

Adenomata taken from nine patients with Cushing's syndrome were observed by electron microscopy. Agranular endoplasmic reticulum was prominently developed in all cases, occasionally fine dotty granules were observed in the tubules of agranular endoplasmic reticulum. Mitochondria showed a wide variety of changes in size, shape and internal structure, and somtimes contained electron dense droplets in their matrix. Mitochondria resembling those in the normal zona fasciculata intermingled with pathologically altered ones, suggesting that the adenomata which caused Cushing's syndrome were derived from the zona fasciculata. Fibrous structures were seen in the cytoplasm in one case. It is proposed that all of the changes in cellular organelles of the adenoma cells are correlated with increased secretory activity.