In human breast tissue, CD34+ cells have been detected in the extracellular matrix surrounding breast lobules and low grade ductal carcinoma in situ (DCIS) but not when SMA+ myofibroblasts were increased surrounding high grade DCIS and invasive ductal carcinoma [25, 26], which is suggestive of differentiating fibrocytes. Here, CD34 is linked to ductal breast carcinoma in situ.