Ultrastructure of aldosterone secreting adrenal adenomata

Two adrenocortical adenomata causing Conn's syndrome were examined by electron microscopy. Adenomatous cells were arranged in small clusters and showed a rather different morphology, especially as far as mitochondria were concerned. Some cells contained mitochondria with lamellar and tubular cristae (zone glomerulosa-like cells), while other parenchymal elements displayed mitochondria with tubular and vesicular cristae (zona fasciculata-like cells). Both cells types were endowed with a quite well developed smooth endoplasmic reticulum, some lipid droplets and a prominent Golgi apparatus. Moreover, adenomatous cells with large masses of lipofuscin pigment granules were also observed (zona reticularis-like cells). These findings stress the structural heterogeneity of the Conn's adenomata.