Metastasis to the brain is a clinical problem in patients with breast cancer (1-3). Between the breast and the brain reside the secondary lymphoid organ, the lymph nodes. We mined published microarray data (4, 5) to compare primary and metastatic tumor transcriptomes for the discovery of genes associated with metastasis to the lymph nodes in humans with metastatic breast cancer. We found that natural cytotoxicity triggering receptor 1, NCR1, also known as CD335 or NKp46,was among the genes whose expression was most different in the lymph node metastases of patients with metastatic breast cancer as compared to primary tumors of the breast. NCR1 mRNA was present at increased quantities in lymph node metastases as compared to primary tumors of the breast. Importantly, expression of NCR1 in primary tumors of the breast was correlated with patient recurrence-free survival, more significantly in lymph node negative patients than in lymph node positive patients. Modulation of NCR1 expression may be relevant to the biology by which tumor cells metastasize from the breast to the lymph nodes and the brain in humans with metastatic breast cancer.