Background: Sentinel lymph node (SLN) biopsy guides breast cancer treatment and prognostication. To date, there have been few studies examining the genetics of SLN metastasis in triple negative breast cancer (TNBC). The aim of this study is to characterize and compare gene expression patterns of primary breast cancers and autologous matched SLN metastases. Methods: Patients with stage 2-3 ER/PR negative, HER2 negative TNBC with macrometastasis to the SLN who did not have neoadjuvant therapy were selected. The tumor-specific area was isolated from breast and SLN paraffin embedded tissue sections. Gene expression of a panel of 2567 cancer-associated genes was analyzed with the HTG EdgeSeq system coupled with the Illumina Next Generation Sequencing (NGS) platform. Results were validated with RNA-scope assays for RNA in situ detection. Results: 18 pairs of TNBC and matched SLN metastasis were analyzed for 2567 genes. Compared with the primary TNBC, SLN metastasis had 34 statistically significant upregulated genes and 31 downregulated genes. SLN metastasis had at least a 5-fold change (FC) in upregulation in 3 genes and downregulation in 3 genes, compared to primary TNBC [Table]. Notably, there was an upregulation of anti-apoptosis and survival signaling genes (i.e. BIRC3) in the SLN metastasis. There was also an upregulation of chemotaxis genes (CCL13, CXCL19, CXCL21, CXCR5, TNFSF11, p<0.001). The most striking feature is the downregulation of genes known to regulate cell microenvironment interaction (MMP2, MMP14, COL1A1, COL1A2, COL5A2, COL6A6, COL11A1, COL17A1). Conclusions: In TNBC, SLN metastasis has a distinct gene expression profile. Genes associated with anti-apoptosis, survival responses, and chemotaxis are upregulated, and genes associated with regulation of extracellular matrix are downregulated. Upregulated and downregulated genes with at least a 5-fold change in gene expression in lymph node metastasis compared with TNBC.