Enrichment of genes expressed at a greater level in intralobular stroma in the Hepatic Fibrosis/Hepatic Stellate Cell Activation canonical pathway, stromal network 3 (collagens, TGFBR2, SPARC, ENG), ECM gene ontology and VEGF signaling pathway suggest that stromal activation is being induced during this period of mammary gland development. This evidence concerns the gene TGFBR2 and fibrosis.