Awaiting PET scan results

My mother was diagnosed with breast cancer about 6 weeks ago.  The tumor was large (3.5 cm, I think).  They did a masectomy and took out all of the lymph nodes under her arm all in one surgery.   17 of the 23 lymph nodes came back positive.  I don't have a lot of other details as I live many miles away and get most of the info by phone.  I do know that the cancer is HER negative.  She had a port-a-cath put in this week and will be starting chemo soon.  My question is, with 17 of 23 lymph nodes testing positive, is there any chance that it hasn't spread anywhere else?  Seems unlikely to me, but maybe someone has a positive story.  My mother is 65 and otherwise completely healthy.  We are all still in shock, but starting to deal with it.  PET scan results this Thursday.

I did't get the impression that it was a fast growing cancer. More likely that it's been there for several years.  She finially went to the doctor due to swollen lymph nodes under her arm.  I do know that when they took the tumor out they said that they had gotten all of the cancer out of the breast.  (I guess that's what they mean by clean margins).  Also, I do believe the doctor said something about hormone blockers after the chemo.  My sister-in-law who lives near her has more info than I do because she goes to the doctors with her. 

Unfortunately, my mother moved to GA a few years ago and I am still in NY.  The 800 miles makes it hard.