Nine key genes (CALR, CCL5, CEPT, FTT3, CXCL13, FLT3, IL12B, IL18, and IL24, <i>p</i> < 1.6e<sup>-2</sup>) of breast cancer were identified, and a prognostic was successfully constructed with a good predictive ability. The gene discussed is IL18; the disease is breast cancer.