B2M and breast cancer: - Breast Cancer Stem Cells (BCSCs): Identified as CD44+/ALDH2+/ALDH6A1+.- Heterogeneity: Inter- and intratumor variation linked to 103 gene downregulations.- Metastasis Genes: PTMA, STC2, CST3, RAMP3.- CNV Clusters: Cluster_4 showed high mutation rates associated with lymph node metastasis.- Immune Interactions: NECTIN2-TIGIT interactions promote immune escape.- Key DEGs in TNBC: B2M, CD52, PTMA, GZMK.