The sentinal LN excision is a relatively new technique. I had a mamogram done a few years ago - at age 29, due to some persistant pain I was having in my left breast. It was negative. I have heard since that I probably should have had a ultrasound done instead, due to the density of the tissue in my breast as a result of my age at the time. The use of US is most beficial for a situation when you have a nodule and you want better definition of it as to whether it is cystic vs solid.
Some radiologists feel that they can see more with a sono particularly in women with dense breasts.
HOwever the xray still is the gold standard and can show many things that the sono can't If there is any concern there is no reason that a person couldn't have both. But the major association with hormone use and breast cancer comes in thee post menapausal area. Some studies show that the use of hormone replacement over and above the ten year level may convey a very slight increase risk of cancer. The benefits of this thearpy still far outway the risks. Imagine a senior community resource with informative content and more.