Proliferation rate (Ki67 index) was significantly increased in AAC (8.0% [4.0% to 17.0%], P < 0.001) and ACC (14.00% [7.5% to 26.50%], P = 0.001) compared with control specimens (1.0% [1.0% to 3.0%]. Here, MKI67 is linked to adrenal cortex carcinoma.