Micro-invasion, rads, and node biopsy

Percy, I'm sorry that you got this news and now have to deal with the confusion about what to do next.  I had a microinvasion, but mine was found during my excisional biopsy.  When I went for a 2nd opinion prior to my MX, the second facility asked for the pathology slides and did their own assessment - and they agreed about the microinvasion. 

With regard to an SNB, my surgeon told me that the risk of nodal involvement, even with just a 1mm microinvasion, was 10%.  Since then I've read studies that confirm this.  So passing on the SNB is a bit risky, since nodal involvement is a whole new ballgame.  A microinvasion on it's own doesn't change much vs. a diagnosis of pure DCIS; adding nodal involvement would be more significant.  The size of the margins is irrelevant to the SNB decision - I have no idea why your surgeon would have said that having large margins around the invasive component means that the nodes don't need to be checked.  Lots of women who have invasive cancer (more than what we are talking about here) have very wide margins but still have nodal involvement.  Perhaps, if your microinvasion really is tiny - much less than 1mm (which is the maximum size for something to be considered a microinvasion; anything larger is a T1a invasive tumor) - your risk of nodal involvement will be lower and the MO will be okay with not checking your nodes.  This is certainly worth the discussion with the MO. 

As for HER2 status, it's possible that your microinvasion might be too small to test.  And really, with just one microinvasion, finding out that the invasive component is HER2+ won't change your treatment plan.  If you had multiple microinvasions, or a invasive tumor that was 5mm in size (or even 4mm), then HER2 status becomes more important, because even small HER2 tumors can be very aggressive.  Treatment guidelines suggest chemo and Herceptin for HER2+ tumors that are 6mm in size or larger, but I've seen some cases where this treatment is given when there are multiple microinvasions, or when the tumor is as small as 4mm. But for a single microinvasion?  I can't recall any situation that I've seen in all my years on this board where Herceptin and chemo were recommended when the amount of invasive cancer was that small.  The fact is that the long-term prognosis for those who have DCIS-Mi is just 1 percentage point different than the long-term prognosis for those who have pure DCIS - and the figure for those with DCIS-Mi includes those who have microinvasions that are HER2+.  So personally, I wouldn't worry about HER2 status (and personally, in my own case, I didn't worry; as was common 8 years ago when I was diagnosed, I never did find out my HER2 status). 

With regard to rads, here is where I believe margins come into play.  If you had just one tiny microinvasion and if it was nowhere near your margins, then I don't know that it should have much, if any, impact on your decision about rads.  I think that consulting with Dr. Lagios is still a good idea, and perhaps is even more important now, given your questions about the microinvasion and whether that should impact your decision on rads. 

Lastly, as for not doing hormone therapy, the only thing that has changed with the microinvasion is that you now face a very small risk of mets - probably at most 1% (but ask your oncologist about this).  Hormone therapy might be able to reduce that risk by approx. 1/3 to 1/2.  The primary benefit for you for hormone therapy after a lumpectomy remains reducing the risk of a local recurrence (and this risk hasn't changed at all with this new news) and reducing the risk of a new primary breast cancer (and this risk hasn't changed at all with this new news).  

Hope this helps!

Staging is done using the TNM system - tumor, nodes, metastasis.  When there is a "P" in front of any of these ratings, it means that the rating is based on a pathological finding, i.e. what was seen in the pathology lab under a microscope. 

So at this point your staging is PT1mi, PNX, MX.  That's Stage I (the T1 tumor moves you from Stage 0 DCIS to Stage I).

The PT1mi means that pathologically you have a T1mi tumor - that's the microinvasion ("mi" stands for microinvasion).  That's the smallest possible T1 tumor.  Women who have pure DCIS have a Tis tumor ("is" stands for in-situ). 

The PNX means that there is no pathological assessment of your nodes. "X" is used when no assessment has been done. 

The MX means that you have no assessment of mets.  This is because you haven't had any screening tests for mets, no CT scan or PET scan.  Most women who have DCIS or DCIS-Mi have this same "MX" assessment for mets, and even many women who have Stage I IDC don't get these tests, so they too have the "MX".  In situations where the risk is considered very low that any mets would be found through screening, the "MX" is considered an acceptable replacement for an "M0", which would mean that there is no mets based on screening that's been done.  So from a staging standpoint, in those cases, MX is treated as though it's M0.

Hope I didn't get too confusing on that.