The Breast Cancer Index (BCI) is another molecular test that consists of two biomarkers, i.e., the Molecular Grade Index (MGI) that is based on the expression of the BUB1B, CENPA, NEK2, RACGAP1, and RRM genes that are related to tumor grade and progression, and the H/I, which is a ratio of the levels of expression of another two genes: HOXB13 and IL17B. The gene discussed is BUB1B; the disease is breast cancer.