I just finished treatment for this same thing, although my tumor was smaller. The “invasive” makes it scary sounding but as you said, it had just spread a bit outside lobule. I had a quite easy lumpectomy followed by radiation. I didn’t need chemo bc lymph nodes were not involved. Everyone told me it was extremely curable and not to panic, so I didn’t and it turned out ok. Honestly, other than some mental anguish anyway, it went smoothly and I feel safe putting it behind me. I have faith that Mayo did what was needed. I am 66 so perhaps a much younger woman may need more aggressive treatment. I’m on an AI for 5 years which I’m not fond of, but just started it and I’ll stop it if I have trouble. I realize I was a lucky one and do not mean to make light of cancer or the severe things some women go through. Just trying to give some hope.