You'll find out more about you cancer (sounds like an unwelcome pet, doesn't it?) once you've had surgery and the pathology report comes back. It will show receptor (positive or negative) as well as type of cancer and other details. It's not always exactly the same as the biopsy indicates so the doctors tend to hold off with too much info until then.
I was the same as you - nothing to indicate cancer - just a routine screening mammo but, although life has been turned upside down since, my situation if it hadn't been discovered, doesn't bear thinking about.