Figure 4 shows the top 30 significant genes that were differentially expressed between matched primary BC and BCBM samples from individual patients. Interestingly, hierarchical clustering analysis revealed that the group that underwent conversion to unfavorable subtypes during metastasis included genes that were upregulated in primary BC compared with BCBM such as KRT14, KRT5, KRT17, MME, and SFRP1, and genes that were downregulated, including MKI67, AURKB, CDC20, and KIF2C. This evidence concerns the gene KRT14 and breast cancer.