In situ is Non-infiltrating , Non-invasive. If cancer cells are outside the ducts then by definition it’s not ‘in-situ’. I don’t believe cancer can be a ‘little’ bit invasive. I know we want to believe that but using incorrect diagnosis is not fair to patient. I k ow things aren’t clear cut but how far from the duct do the cancers have to be to be considered stage 1A? Just askin’ because this type of information gets generated and picked up by others & then becomes the way of thinking. It’s not helping the patient by sugar coating & I k ow we all want to hear the lesser diagnosis. God Bless you all.