Adrenal cortical neoplasms include adenoma and carcinoma that have been traditionally differentiated using specific classification systems based on morphological criteria not including Ki67 evaluation: the Weiss system [111], the reticulin algorithm [112], the Lin-Weiss-Bisceglia system for oncocytic neoplasms [113], and the AFIP system for pediatric neoplasms [114]. This evidence concerns the gene MKI67 and adenoma.