p53 and Ki67 in adrenocortical tumors

The p53 tumor-supressor gene has been reported as the most frequent genetic abnormality seen in human malignancies. Here we studied immunohistochemica lly the expression of p53 in a large series of adrenocortical tumors. The p roliferative activity was assessed by the expression of Ki67. Tumor materia l consisted of 60 adrenocortical adenomas and 27 adrenocortical carcinomas. A tumor was scored as positive for p53 if more than 10% of the cells showe d nuclear staining. All adrenocortical adenomas were negative for p53 and t he percentage of Ki67 positive cells was mostly 1-2% but never exceeded 5%. Hormonal activity did not reflect the proliferation index. Adrenocortical carcinomas, however, behaved differently depending on hormonal activity. 10 /13 of non-functional, 0/3 Conn`s, 3/7 Gushing's and 3/4 virilizing carcino mas were positive for p53. The proliferative activity was also higher in no n-fuctional carcinomas compared with hormonally active tumors. Our data sho w that majority of adrenocortical carcinomas are positive for p53, whereas all adenomas are negative. Hormonal activity of carcinomas reflects both p5 3 status and proliferation index. Thus, immunohistochemical levels of p53 a nd Ki67 are higher in hormonally inactive adrenocortical carcinomas.