Electron microscopic study to compare preclinical Cushing's syndrome with overt Cushing's syndrome

No significant differences in gross and light- microscopic features have been reported between preclinical and overt Cushing's adenomas. In this study, the ultrastructural differences between the two syndromes was attempted to be clarified.

Two preclinical Cushing's syndrome adenomas and two overt Cushing's syndrome adenomas obtained from surgical extirpation were examined in an electron microscopic study.

Light microscopically, the adenomas of both syndromes were composed predominantly of clear cells, with few compact cells. Ultrastructurally, the prominent differences were of development in each organelle: the preclinical Cushing's adenomas had undeveloped mitochondria, which were smaller in size and had sparse cristae, lysosomes and polysomes, whereas the overt Cushing's adenomas contained well-developed mitochondria which were larger in size and were filled with abundant cristae, smooth endoplasmic reticulum (SER), lysosomes and polysomes.

Preclinical Cushing's syndrome adenomas were ultrastructurally characterized by a reduced number of cellular organelles such as mitochondria and SER, which are necessary to synthesize glucocorticoid hormones. However, examination of a greater number of adenomas will be required to be able to draw conclusions on the ultrastructural differences between the two syndromes.