9 cm DCIS - Mastectomy / Second Opinion?? / Tamoxifen

I think all I can suggest is maybe explain your reasons for not wanting the mastectomy and see if you can get a re-excision. *Lots* of women with DCIS need a second surgery to clean up margins. I did in 2016. As you know, it's an easy surgery with a very quick recovery. Re: the Tamoxifen--it can be an important part of helping to prevent a recurrence. There's lots of support on this site. You should not assume you'll have bad SEs and definitely give it a shot if you're highly ER+.

Here's a different perspective, based on my experience.

I originally had an excisional biopsy (after a stereotactic biopsy finding of ADH) which removed two large areas of high grade DCIS along with a microinvasion of IDC. There were no clear margins anywhere around either area of DCIS. My preference was to have a re-excision rather than a MX but an MRI done after the excisional biopsy showed that my breast was full of DCIS. So it was clear to me that a re-excision would be unsuccessful and I reluctantly agreed to the MX. I had a UMX with expander-to-implant reconstruction. In the end I had over 7cm of DCIS spread over those two areas in my breast.

I didn't drive for a couple of weeks after my surgery but I was outside walking to the grocery store less than 48 hours after surgery. I might have been extremely lucky, but I think for most women a MX does not mean that they are laid up for 6 weeks but rather that they have to be careful with their arm movement (no heavy lifting, no pulling or pushing or stretching too much) for 6 weeks. I remember reading that when skin is cut, it takes 6 weeks to regain 90% of the strength/resilience of the skin. So the reason for the six week rule is to ensure that the external and internal stitches and incisions aren't damaged. But I think most of us who've had a MX find that there is a lot we can do within a couple of weeks.

If your final diagnosis is DCIS (or DCIS-Mi, like mine), you will not need Tamoxifen after a MX, unless your surgical margins are too close. This recommendation comes from the MO, not the surgeon. With such a low recurrence risk after a MX (1%-2%, unless margins are close) the benefit from Tamoxifen is small. The only reason to take it is to address the breast cancer risk of the other breast. Having been diagnosed one time, you are now higher risk to be diagnosed again. But this is a lifetime risk and like anyone who is high risk, you can opt to take hormone therapy or you can choose not to. And you can make this decision at any time - there is no urgency. My MO actually recommended against Tamox. after my UMX.

Have you had an MRI? If not, I would recommend it. It will help you and the surgeon know how widespread the DCIS appears to be, and whether a re-excision might be successful or is likely doomed to fail