HOXB13 and neoplasm: BCI (Biotheranostics, Inc., San Diego, CA, USA) is a predictive multi-gene expression assay that incorporates: (1) the HOXB13:IL17BR ratio, which is associated with tumour responsiveness to endocrine therapy; and (2) the molecular grade index, which is associated with tumour proliferation, and is based on the average expression of five cell cycle-associated genes [42,43].