Rolled CC and SL views are very useful in workup of summation shadows. The degree of difference between the original image and the repeat image does not have to be much either; sometimes even a slight difference in compression will show the summation shadow disappears. In the case above note, the change in position by the profile of the nipple; the second view is technically superior to the first.

In everyday practice, the rolled CC and SL views are more useful than mag views with asymmetry of the parenchyma. I reserve mag views for calcifications; they take time and extra effort in practice while the rolled CC and SL views are quick and easy. A magnified view of a blob rarely gives added useful information.

If the asymmetry is not present on the other view of the same breast, you are likely dealing with a parenchymal asymmetry.  Always look for the "lesion" on the other view before you do anything else. The converse is true as well; if the lesion is on the other view, it's likely real. Then full workup including ultrasound should be done.

Do not be tempted to skip ultrasound; it adds value.