Studies of the last decade have demonstrated that the morphological and immunophenotypic patterns of adrenocortical carcinoma (ACC) have a high heterogeneity in both the occurrence of various tumors and the development of a solitary tumor. Carcinogenesis of ACC, like most neoplastic processes, is associated with mutations in at least 15 driver genes, with a wide range of chromosomal aberrations, epigenomic changes, and alterations of the microRNA profile. According to the literature, isolated genetic damage is also insufficient for the manifestation of the malignant phenotype of adrenocortical cells. Knudson’s two-hit hypothesis is implemented in at least germline mutations: the development of ACC requires a second genetic event occurring in somatic cells, which leads to inactivation of the second allele of the gene. ACC is an extremely heterogeneous disease, which determines the complexity of differential diagnosis with benign adrenocortical tumors and that of prediction of the clinical course. Another no less important issue is the lack of valid predictors for the efficacy of mitotane, the use of which may be associated with severe adverse effects.