In sum, we utilized machine learning and WGCNA of large-scale data from the GEO database to identify prognostic gene set of ABHD11, DDX39A, G3BP2, GOLM1, IL1R1, MMP11, PIK3R1, SNRPB2, and VAV3 involved in the distant metastasis for BC patients with small tumor size. This evidence concerns the gene PIK3R1 and breast cancer.