Collectively, we propose STAT5a as an important player into both DCIS formation and invasion and its phosphorylation on tyrosine 694 (Y694) should be given closer attention as a potential target to prevent DCIS formation and transition to invasive cancer in a subset of high risk patients such as those with a Cav-1 negative cancer stroma. Here, STAT5A is linked to ductal breast carcinoma in situ.