My cancer was caught early and I opted for mast. and no chemo. After the mast, the tissue was examined and no cancer was found. I started on tamoxifen, stopped that and started arimidex.
Hopefully for your Grandmother, the lump is beign. I can tell you first hand...I had my mast. 3 years ago and it seems like my energy level is at an all time low. I usually blame the med that I'm on but it could be the surgery.
Hang in there and keep doing what your doing: trying to learn about the disease and being supportive for your Gran.