Background: The detectability of adrenal incidentalomas (incidentally found adrenal tumours) in the whole population is estimated at 0.1%; 0.42% in non-endocrine patients and at 4.3% in oncologically diagnosed ones. Even up to 16% of incidentalomas of adrenal glands can be malignant lesions. The issue of crucial importance is the histopathological differentiation between benign lesions and malignant tumours of the adrenal cortex and medulla. Objectives: To evaluate whether the immunohistochemical analysis of the expression of p53, p21, PCNA and Ki67 in the tumour's tissue can be useful in the histopathological diagnostics of adrenal incidentalomas and whether it is important for prognosis. Material and methods: Our series consisted of 74 tumour samples from 164 patients operated for incidentalomas. There were 43 cortical adenomas, 11 cortical adrenocarcinomas and 20 PHEOs (including 5 malignant lesions). Using monoclonal antibodies, the expression of p53, p21, PCNA and Ki67 was evaluated. Results: We found a statistically significant correlation between the expression of p53, p21, Ki67 and the differential diagnosis of adrenal cortical adenoma and adrenocortical carcinoma (for proteins: p53 p = 0.010, for p21 p = 0.010, for Ki67 p < 0.001). The statistical significant correlation between PCNA protein and diagnosis of adrenal cortical adenoma and adrenocortical carcinoma was not found. The statistically significant correlation between p21, PCNA proteins and the diagnosis of benign and malignant PHEOs was not estimated. There was no expression of Ki67 or p53 protein above the assumed level in benign and malignant pheochromocytomas. The statistically significant correlation between p53, p21, PCNA or Ki67 and the occurrence of metastases in adrenocarcinoma and malignant PHEOs was not found.
