Contrast these mature linear calcifications in an ordered ductal distribution with the "wild and crazy" calcifications of DCIS. These all have more or less the same density; there are no "Xs Ys and Zs" of DCIS. They are literally calcified casts of the ducts. This is a benign process and I see it most often in older ladies. It can progress with time but you will not confuse it with DCIS.
The distribution may be segmental but the nature of the casts is typically benign. The left margin of the image shows subtle vascular calcifications in a typical "tramline" distribution of the arterial wall.