Are the close margins by the skin or the chest wall? If they are by the skin, one option is to remove more skin. I did that when I ended up with a 1mm margin right near the scar line.

Even though your diagnosis is DCIS, if some cells remain and develop into a recurrence, more than 50% of recurrences after a MX for DCIS are not discovered until they are invasive cancer. Additionally, while on average the recurrence rate after a MX for DCIS is 1%-2%, with close surgical margins some studies (but not all) put the recurrence rate into the mid-teens. Because of this, some MOs suggest radiation or hormone therapy to reduce the risk.

Here is a recent thread where this was discussed. In my post in this thread (first post in response to the OP) I provide a link to another discussion thread about this topic, and in that thread, there are several more links. So this is not a unique situation and there's been lots of discussion about it, which might be helpful to you.

Topic: DCIS + Mastectomy + Radiation?!?!?! https://community.breastcancer.org/forum/68/topics...

Six years ago when I had a similar situation, this was unique. I researched for hours to decide what I should do. I was not interested in reconstruction and was not tolerant of increased risk at that time, so opted for radiation to cut recurrence rate from 13% by 50%. Narrow margins in a Mx are not the same as a positive margin. Your risk may be far less. Some researchers still state that any margin is a negative margin. My positive margin was microscopic and my bs stated that the solution the sample is placed in post Mx causes the tissue to shrink. So some narrow or positive margins, if microscopic may have indeed been negative. I have no recommendations for you as it is an individual decision with no scientific basis to help you decide. It is based upon your tolerance for increased risk, your future needs and preferences. Whatever you decide, your prognosis is excellent