Hi cdelv, when you have multifocal DCIS, it is sometimes difficult to estimate the size of the pathological area, due to it's multifocal nature, so it's generally an estimate.  Are you getting an MRI? That might help determine how much DCIS remains, and whether lumpectomy would be sufficient vs. mastectomy.  I will say that the general rule I have been told is that if the DCIS is estimated to be more than 4 cm, mastectomy is recommended because of cosmetic issues (as Annette alluded to).  It can also be difficult to achieve wide clean margins.  I had probably between 5 and 6 cm, but I was able to achieve clean margins on a third lumpectomy.  I should state that I had only one narrow or not clean margin after the second surgery, so that is probably why the surgeon allowed me to try for the third lumpectomy.  The cosmetic result isn't perfect (also because I had three prior surgeries on that side).  You may need to go to mastectomy.  Generally, you wouldn't need radiation if you do a mastectomy for DCIS, but in rare circumstances individuals have had to have it, if they still have narrow margins at the chest wall even after the mastectomy.  Don't worry about over treatment with high grade DCIS with necrosis. Best of luck to you.

66- while you want to make decisions and get treatment going don't feel like you have to rush out tomorrow with the "right answer" - If you are having more surgery regardless of type and if your surgeon lets you just get yourself on the surgery schedule then work on exactly what you want to have done- i.e reconstruction vs not.

You will hear all different experiences here- but at the end of the day have to make your own decisions.  I am "making this up" but if you always had regular mammo and they saw the first suspicious "stuff"  last year then 6 mos later found something they are classifying as high grade- its a great thing that you had that bx and the re-evaluation got you going on treatment and no pathology indicating anything invasive has happened.  

It sounds like you are giving lumpectomy a fair shot but just not getting margins that are acceptable- in that case perhaps having the mastectomy gives you not only removal of breast tissue but not a cosmetic result where there are chunks/hunks (sorry I know that sounds kind of graphic) removed and some breast tissue left.  We will be here for you as you go through this part of your journey

cdelv66, if you haven't already done so, reading this thread might be helpful: 

Topic: A layperson's guide to DCIS

Building on the previous posts, one of the things that I find very frustrating is that in all the articles about over-treatment of DCIS, rarely do you see any mention of the fact that DCIS is a very heterogeneous disease - there are lots of different ways that DCIS presents. 

Some women have a DCIS diagnosis that is a small (sometimes as small as 3mm) single focus of grade 1 DCIS.  Other women have a DCIS diagnosis that is multi-focal, with a large (sometimes as large as 10 cm) area of grade 3 DCIS with comedonecrosis.  And there is everything in between.  

A woman with that first type of diagnosis might be able to get away with just a small lumpectomy (without radiation) - and a handful of doctors might even suggest that watchful waiting would be an acceptable (although not yet standard) option.  A women with that second type of diagnosis almost certainly needs a MX, and if the margins are close to the chest wall, might even be advised to have rads after the MX. 

There are two key differences between a non-aggressive DCIS diagnosis (such as my first example) and an aggressive DCIS diagnosis (such as my second example).  

First is that an aggressive DCIS presents a greater risk that some invasive cancer might be found mixed in with the DCIS.  In other words, after all the surgery is done and all the suspicious breast tissue is removed, it might turn out that the final diagnosis isn't DCIS but actually is IDC. On average approx. 20% of needle biopsy diagnoses of DCIS are upgraded to invasive cancer (usually just a microinvasion, but sometimes more) once all the pathology info is available.  For someone with a non-aggressive preliminary diagnosis, the risk is much lower, whereas for someone with an aggressive preliminary diagnosis, the risk is much higher. 

Second is that an aggressive DCIS presents a greater risk of recurrence, and a greater risk that any rogue cells left behind might develop into invasive cancer within a shorter period of time.  So this means that someone who has an aggressive DCIS needs to be more careful (than someone with a less aggressive diagnosis) to ensure that all the DCIS cells really are removed and/or killed off.  This is why skipping rads (for someone who's had a lumpectomy for DCIS) might be considered relatively low risk for someone who had a small amount of low grade DCIS, but would be much higher risk for someone who a large amount of high grade DCIS.

What this all means is that with DCIS, what is over-treatment, and what is under-treatment, depends on the specifics of the diagnosis.  DCIS cannot be approached as a single diagnosis with a one-size-fits-all treatment standard.

But then there's the good news.  All DCIS - no matter how much you have, no matter whether it's a single focus or multi-focal, no matter the subtype (even the most aggressive comedo-type DCIS), no matter the grade, no matter the hormone status - is all Stage 0.  And that means that DCIS cells, whatever the type, cannot invade into the body.  So pure DCIS is always a pre-invasive cancer, and is never life-threatening in and of itself.  The threat from DCIS comes from the fact that if not properly/adequately treated, it can lead to the development of invasive cancer. 

As for how to measure the size of DCIS, I don't know the official rules on this but personally I see it to be different than how it's handled with invasive cancer.  With invasive cancer, the size of the tumor determines the stage and to some extent, the treatment plan.  So there can be a big difference in diagnosis, staging and treatment if someone has multi-focal tumors and the tumor sizes are added together vs. not added together.  If someone has a 1.4 cm tumor and a 0.8 cm tumor, they are  considered to be Stage I based on the size of the largest tumor; the rule is that invasive tumor sizes should not be added together.  If they were to be added together, this would increase the tumor size to 2.4cm, and that would be a Stage II diagnosis. 

With DCIS, no matter how much DCIS you have, it's always Stage 0.  With DCIS, a multi-focal presentation tends to suggest a greater likelihood that some invasive cancer might also be found, and increases the risk of recurrence. And with DCIS, even when it's multi-focal, the cancer cells are usually all found in a single duct of the breast (a single duct can wind throughout the breast).  So from the standpoint of truly understanding the diagnosis and the implications of the diagnosis, I think with DCIS it is important to add together the different sizes of a multi-focal lesion.  In my case, I had two areas of DCIS and I had two surgeries.  So the assessment of the size of my area of DCIS is the approximate sum of all of that. 

Lastly, as for Tamoxifen, if you have a MX for DCIS and if you have adequate surgical margins, your recurrence risk will likely be in the range of 1% - 2%.  Normally Tamoxifen would not be recommended when the risk is that low.  However if you have a single mastectomy, you will still have one healthy breast, and your risk to develop BC again will be higher than average, thanks to the fact that you now have a personal history of breast cancer.  So Tamoxifen might be recommended as a way to lower your risk of a new primary, a breast cancer that might develop in your other breast.  Tamoxifen is certainly optional for that.  In my case, I had a large amount of very aggressive DCIS and had a single MX.  My oncologist discussed Tamoxifen with me, and was willing to prescribe it if I wanted to take it, but he didn't actually recommend it.  I did my own research and decided to not take it.   But other women in a similar situation, having had a single MX for DCIS, do choose to take Tamoxifen.  It's really a question of personal choice.