Expression levels of the large subunit of ribonucleotide reductase M1 (RRM1), cytochrome P450 2W1 (CYP2W1), and sterol- O-acyltransferase-1 (SOAT1) are considered as potential predictors of response to mitotane therapy.AIM: To assess the immunohistochemical expression of RRM1, CYP2W1 and SOAT1 in ACC as markers of clinical outcomes and response to the therapy with mitotane.MATERIALS AND METHODS: The study included 62 patients older than 17 years of age with a diagnosis of ACC confirmed histologically and immunohistochemically. The gene discussed is RRM1; the disease is adrenal cortex carcinoma.