Anne-
So sorry for what you are going through and having to wait the weekend for your test. I think it's really common to have additional tests, only as a precaution to make sure the cancer hasn't spread.
I am a breast cancer survivor, almost 3 yrs out. I did have an MRI but no other tests, but as I say, i think it is very common to have extra tests and it depends partly on what your breast surgeon and the oncologist might think is appropriate. - BUT it in no way means the cancer has spread.
It is terrifying and sureal at 1st to get this diagnosis. Getting all your records,tests is a great idea. Have the Dr. explain these thouroughly when you get results. Once you have discussed treatment and have a plan, you will feel a little more in control.
We are here for you, so keep in touch and let us know how you are doing.

Leea