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IDC and DCIS in the same tumor?

rleepac Member Posts: 193
edited September 2019 in Mixed Type Breast Cancer

on my path report it says there was both IDC and DCIS in the same 2.1 cm mass. Not really sure what that means? Does that mean some of it was still at the 'in situ' stage and some of it progressed to IDC? Wouldn't that make it all IDC? I'm confused!


  • exbrnxgrl
    exbrnxgrl Member Posts: 4,933

    Both can exist. At this point, it doesn't really matter as you will be treated for the IDC, not DCIS. best of luck to you

  • rleepac
    rleepac Member Posts: 193

    Ok. That makes sense. Thanks.

  • ananda8
    ananda8 Member Posts: 1,418

    My tumor, 2.4 cm, held DCIS and IDC. I had radiation and 5 years of Arimdex, no chemo. I'm almost 7 years out.

  • Blownaway
    Blownaway Member Posts: 662

    I had both side by side

  • cp418
    cp418 Member Posts: 359

    I had a total 1.8 cm mixed mass of DCIS and IDC. It was described as the center being 0.5 cm DCIS surrounded by IDC. Wish it was found when it was still DCIS.....

  • flautadulce
    flautadulce Member Posts: 1

    I have both DCIS and IDC. I've been told that there is disagreement among oncology specialists about whether IDC is a DCIS tumor gone bad or if they are 2 distinct cancers. My DCIS tumor was 10x larger than the IDC tumor. Personally, I think DCIS becomes IDC if left too long.

  • Member Posts: 1,435

    Flautadulce, my understanding is that it is believed that approx. 85% - 90% of IDC develops from DCIS. I wasn't aware that there was any disagreement about that. What isn't known, however, is what causes DCIS to evolve to become IDC. In my 11 years reading up on this, I've seen dozens of theories and research studies about this, none that have as yet come to a clear and definitive conclusion.

    Because most IDC develops from DCIS, it is very common to find IDC tumors that include a very small amount of DCIS. This probably happens more often than not.

    Similarly, it is very common to find DCIS tumors that include a very small amount of IDC. I had over 7cm of DCIS along with 1mm of DCIS. DCIS-Mi, my diagnosis, is in fact separately identified as the very first level of Stage I invasive cancer. The "Mi" stands for an invasive tumor that is 1mm or small in size.

    For those who have a combination of DCIS and IDC, the staging is based on the size of the IDC. The DCIS is not added in. This is why I am Stage IA, despite having so much DCIS. The only thing that counts in my staging is that 1mm of invasive cancer.

    Here's what I think is the big question, and which I have never yet seen researched:

    Why do some tumors that start as DCIS almost immediately evolve to become IDC and then continue to develop and grow as IDC? (i.e. those tumors that are found to be mostly IDC with just a small amount of DCIS),


    Why do other tumors that start as DCIS continue to develop and spread as DCIS but at some point also have a tiny breakthrough of invasive cancer? (i.e. those tumors that are found to be mostly DCIS with just a small amount of IDC).

    I suspect that although both these types of cancer include DCIS and IDC, they might be very different in genetic make up and in terms of what triggers the development of the IDC and the continuing growth of the cancer.

  • Dafne
    Dafne Member Posts: 35

    Beesie, I could not have said it better if I tried.

    My thoughts exactly... Wish there was an answer to this. I just hope there will be an answer in the future. If not for us, at least for the women that follow...

  • 32B
    32B Member Posts: 186

    I was diagnosed with DCIS and eventually was found to have "micro-invasions" of IDC. It seems common. Good to talk to people in a similar boat as it is a bit confusing.

  • letsgogolf
    letsgogolf Member Posts: 65

    I don't think having DCIS and IDC makes it a mixed type tumor. My understanding is that a mixed type tumor is one tumor that has properties of two types of breast cancer such has Lobular along with Ductal. Mine was Ductal with Lobular features and was also referred to as "Mixed Type". I don't think LCIS with Lobular or DCiS with Ductal would qualify as mixed type. Somebody please correct me if I am wrong.


    letsgogolf, that's my understanding as well.

    If DCIS (ductal in-situ, i.e. non-invasive) and IDC (invasive ductal) together in the same tumor was to be classified as "Mixed Type" (or ILC and LCIS) then the vast majority of cancers would be"Mixed Type".

  • letsgogolf
    letsgogolf Member Posts: 65

    Beesie, Good point. I think you are exactly right.