I was diagnosed with DCIS 3/15. Had lumpectomy with clear margins Lt. breast. I had mammo, US, and MRI every 6 months. At 18 month I felt a "fullness" in my Lt. breast. Two tumors were found when I went in for my routine US, and MRI. That may be what you are feeling. If you are checking the full breast more often, it may be irritation you are causing. You already know you have a lump. You are scheduled for a biopsy. Leave the breast alone if you are checking it often (easy to say, hard to do). Good luck, and stay positive. Breast Cancer is NOT an automatic death sentence. Millions of us are survivors. Keep in touch.