DCIS and IDC: what the terms mean
Understanding in-situ and invasive breast cancer
The short version
DCIS (ductal carcinoma in situ) means abnormal cells are contained within a milk duct. IDC (invasive ductal carcinoma) means the cells have grown beyond the duct into nearby breast tissue.
In situ vs. invasive
stands for ductal carcinoma in situ — "in situ" means the abnormal cells are still contained inside a milk duct and haven't spread into surrounding breast tissue. It's sometimes called a non-invasive or pre-invasive condition.
stands for invasive ductal carcinoma, meaning the cells have grown through the duct wall into nearby tissue. It's the most common type of breast cancer. , invasive lobular carcinoma, is a less common type that starts in the milk-producing lobules rather than the ducts.
A DCIS diagnosis is often considered highly treatable, and treatment approaches for DCIS can look different from those for invasive cancer — it's worth asking your care team specifically how your diagnosis is being categorized.
Questions you may want to ask
Is my diagnosis in situ, invasive, or both?
How does that affect the treatment you're recommending?