Immunofluorescence microscopic evaluation of the intermediate filament expression of the adrenal cortex and medulla and their tumors.

Normal adrenal glands (10 specimens) and adrenal gland tumors (58 cases) were immunohistochemically evaluated for different types of intermediate filament (IF) proteins. Some of the normal cortical cells showed cytokeratin positivity, and no positivity was seen for epidermal keratin or other types of IF. In the adrenal medulla, neurofilament positivity was seen in nerve axons, some ganglion cells, and chromaffin cells; and cytokeratin-positive cells could not be detected. Only the vascular and connective tissue elements showed vimentin positivity in both cortical and medullary areas. In half of the cortical carcinomas (13/25), cytokeratin-positive tumor cells were found. Furthermore, vimentin-positive tumor cells were present in 10 of 25 cases, in some of them together with cytokeratin-positive cells. Thus, the results show heterogeneity among the adrenal cortical carcinomas. Interestingly, many benign adrenal cortical tissues and some carcinomas lacked immunoreactivity for all types of IF, suggesting a poorly developed IF system in these tissues. In contrast to adrenal cortical tumors, pheochromocytomas contained neurofilamentlike immunoreactivity. These results reflect the different cellular nature of adrenal cortical and medullary tumors, which apparently can be distinguished from each other with antibodies to intermediate filament proteins.