In this paper we identify genes that could be principal in breast cancer primary tumor and its firstmetastasis in lymph nodes, within biopsies in GEO and GDCDP database. By applying Information-Theory-based algorithms for processing gene expression profile matrices, we got the genetic networks ofnext tissues: 1) breast cancer free, 2) breast cancer primary tumor, and 3) first metastasis of breastcancer in lymph nodes. The topology analysis in the genetic networks allows for identifying gene-nodesdegree and the mutual information between pairs of genes. The late gene ontology based analysis on themolecular and functional character of genes with highest degree and mutual information confirm theirrelevance in the mentioned processes and reveals specific signaling pathways signature in cancer-free tissueand in the tumor microenvironment associated with primary and metastasis requirements. As well, thestate-of-the-art review on genes functional role identify tumor-suppressor genes in cancer-free tissue andproliferation and migration-associated genes in cancer.