DCIS and surgery

I'm hoping someone here can help me! I'm seeing a breast surgeon on the Gold Coast who suspects I have DCIS as I have a painful bleeding duct. I am having an MRI on Thursday as nothing showed in the mammogram (tissue too dense) or ultrasound. The pain I am experiencing is on the outer lateral side of my breast, almost as deep down as my chest wall. My breast surgeon wants to excise the duct regardless of the MRI findings, but only 4cm of duct from the nipple. I am worried that if it is DCIS that the surgery may do two things I am extremely concerned about. 1. It may not remove enough of the duct especially as my pain is so lateral (much further than 4cm from my nipple)! This may result in a negative biopsy of the tissue. 2. She may disturb any cancer that's there and introduce the cells into the healthy tissue of my breast. I asked her if she can please remove the duct in its entirety but she said 4cm is usually enough. What should I do? I'm freaking out enough as it is without having to worry about a bungled surgery and diagnosis.