I believe it is standard procedure with this diagnosis. I have the same thing but decided the 3% or so less chance against the side effects were not worth it. I don't do well with meds, you could have better luck.
This is the standard recommendation with your diagnosis. Tamoxifen does decrease the risk of developing breast cancer. Frequent monitoring should be done but this does nothing to reduce the risk of the development of cancer. There are side effects and you should discuss this in detail with your Physician although not all women experience these. The standard course is 5 years. Regards .....