https://www.bcna.org.au/understanding-breast-cancer/types-of-breast-cancer/ductal-carcinoma-in-situ/https://www.bcna.org.au/understanding-breast-cancer/types-of-breast-cancer/#earlyThe links describe the difference .
It may be they disgnosed dcis initially. But with positive nodes and then further axilliary clearance I think you'll find it is now considered idc. It's common to have a different result after surgery...hence why retested and then chemo being offered etc.
It doesn't alter your treatment plan. My Doctor never discussed stages etc with me...just saying it's small but aggressive treatment was offered due to its grade. I think they don't like to get caught up on the stage and grade too much with us as it isn't particularly helpful (for our heads).
Do you have copies of your pathology following surgery?
This link describes the diffetent aspects of understanding a report.
https://www.cancer.org/treatment/understanding-your-diagnosis/tests/understanding-your-pathology-report/breast-pathology/breast-cancer-pathology.html 
