Pathologists are highly skilled at the evaluation of adrenal neoplasms. Occasional adrenocortical tumors can be diagnostically challenging and supplementary tools can assist in these cases. Histologic and molecular studies support a model that includes 2 broad classes of adrenocortical carcinoma with distinct somatic genetic alterations and clinical outcomes. Pathologists should endeavor to grade adrenocortical carcinomas to assign each case into one of these 2 classes. Mitotic grading by mitotic counting and Ki-67 immunohistochemistry represent the most practicable and informative methods currently available.