Diagnosed with Stage 1 DCIS microinvasive,ER/PR+,her 2 + ,node -

Sorry to hear about your diagnosis. Dancetrancer had DCIS AND 3mm of IDC, ER/PR+ and HER 2 +. She has researched the issue beyond the NCCN guidelines. I strongly recommend that you read her thread and PM her! Good luck!

momof2minnies, I'll second what dancetrancer said.  Although there may not seem to be a big difference between a 1mm microinvasion and a small invasive tumor that's only 3mm in size, even such a small difference in size can be significant.  This is simply because the larger the tumor, the more cancer cells, and the more cancer cells, the greater the risk that one or a few of those cells might have moved from the breast into the body.  There are 300% more cancer cells in a 3mm tumor than in a 1mm tumor, and that's why a 3mm HER2+ tumor might warrant additional treatments whereas a 1mm HER2+ tumor would not. 

So knowing for sure that your microinvasion is a true microinvasion - it's no larger than 1mm in size - is very important. 

Perhaps they didn't list the size b/c it is indeed less than 1 mm?  The only way to know for sure is to ask the pathologist.  I would call the pathology lab or ask your breast surgeon.  If you are not comfortable with the pathology lab and/or would just feel better with a 2nd path opinion, you can have the slides sent to another facility for a 2nd pathology opinion.  Hope that helps!!! 

Linda, I thought I would just repeat here our exchange from the PM.  You indicated that the pathology report lists the area with the microinvasion as "PT1mi".  

In conversation the word "microinvasion" can be used very loosely to describe any small area of invasion but if a pathology report uses the word "microinvasion" or lists the tumor as being "T1mi" (or PT1mi, which means it's based on the pathological findings) then you do have a true microinvasion, i.e. an invasive tumor that is no more than 1mm in size. If a pathologist writes it, then we can be pretty certain that it's based on the official definition. 

That's good news!  

It sounds like you had a good discussion with the surgeon and got all the information you asked about.  Great news on the margins, and good too that the surgeon confirmed that you have a true microinvasion. 

You're right that with pure DCIS, often they don't even test for HER2 status.  Sometimes they do, but there is nothing that they do with that information, since there is no difference in the treatment plan for those who have HER2+ DCIS vs those who have HER2- DCIS.  There are a couple of clinical trials underway but at this point there are no drugs approved specifically to treat HER2+ DCIS.  And in fact the research at this point isn't clear on whether there is any difference in risk or aggressiveness with HER2+ DCIS vs. HER2- DCIS.  HER2 status is one area where IDC and DCIS are quite different, at least for now based on current medical/scientific knowledge.