In this study, we aim to investigate the expression pattern of CXCL9 and its relevance to prognosis in distinct molecular subtypes of BC, as well as the features of various tumour-infiltrating immune cells according to the levels of specific marker expression by employing a number of renowned databases, including the Oncomine, Tumour Immune Estimation Resource (TIMER), and Kaplan-Meier Plotter, etc. The gene discussed is CXCL9; the disease is neoplasm.