Sorry to hear that you are going through this. There really is nothing definitive they can tell you until they complete all the necessary tests. When I was diagnosed in 2006 with Stage II.
The day I got my mammogram, a well defined, solid lump was clearly seen on the film; they were able to give me a biopsy the same day, in the office. They used a needle to aspirate the breast, or remove cells from both the breast tissue and the lymph node (upper outer quadrant on my right breast)... I had felt a soreness, off and on when I exercised but when I felt the area could not feel anything. When I did a breast exam lying down with one arm behind my head, etc... I could not feel a lump, but I had a nagging feeling that something was wrong.
I called my pcp that Monday and saw her the next week. She performed the breast exam with me laying down and could not feel a lump either. So she had me sit up and stand up. It was only then that a lump could be felt, but it felt more like a cyst than breast cancer because it was not really that hard, but to me it just felt like it should not be there. Anyway, the biopsy in the office confirmed breast cancer and it had also spread to the lymph node. So the next test was a breast MRI. After the breast MRI came the surgery to remove the tumor and also the affected lymph nodes, 3 total.
Your MRI should show them what they need to know in order to let you know something. It does not have to be breast cancer, just take it one step at a time. If you have any questions just let me know.
Good luck. Please keep us posted. ~ Dee