Thank you, I appreciate your thoughts and time.
The shortest answer would be "for comparison" ... with such a long time between Mammograms (usually only 1 year) it isn't surprising that there may well be differences. "Normal" is a very broad and loose term and having reviewed your films of 6 years ago additional views may be very helpful to clarify certain findings. I would advise yearly Mammograms and perhaps Ultrasound also in the future. It isn't a matter of which film supercedes (as you say) the other but rather being cautious and defining the differences. Regards ....