DCIS is described as cancer cells confined to the duct.
LCIS is described as cancer cells confined to the lobe.
LCIS is NOT considered cancer, but DCIS is considered early-stage cancer. Some in the medical community want to classify DCIS like LCIS - not a true cancer. Researchers are trying to determine which DCIS cancers become invasive and therefore life-threatening. Some DCIS remains in-situ and does not pose a threat... just not sure which ones so they are treated aggressively.

DCIS has the same characteristics as IDC (invasive cancer), but is contained with the ducts. My tumor was 20% DCIS and 80% IDC, meaning that 80% of my cancer was outside the ducts. But they shared the same pathology. In my opinion, I don't know why any doctor would call it pre-cancer. It is cancer that is pre-invasive.

I have or had Triple negative Breast Cancer and I am still trying to figure. Out what is this. There are so many forms of Cancer you just can't keep up with them

Docs don't consider it cancer until it leaves the milk duct. However all of us who have had it do. I had IDC on the left and DCIS on the right at the same time. I tell people I had cancer in both boobs! They all agree with e and think the docs are crazy.

I am stage 2 Breast cancer then I was told l had DCIS stage zero 0 Nov 2022
Same breast diagnosed in 1987 resulting in lumpectomy.
Long story being that l had radiation in 1987 l could not have again. Feb 2023 l had double mastectomy my choice to do both.
I asked my dr at this point what stage. He said stage II.