Dx DCIS, SURPRISE microinvasion found 5 wks post surgery!

Well.  The same thing happened to me.  I was dx with low-grade DCIS in core biopsy 11-1-13.  Lumpectomy 12-11 path report (final) was given to me as all DCIS, grade 1-2.  A week later, my BS called and said the report had been amended to include a micro.  Very upsetting, as it should not have been presented as final when the pathologist was still checking one slide.  Anyway; same situation, what to do about the SNB?  I researched, asked here a lot, talked to the docs a lot.  My BS and MO said it wasn't necessary, my RO agreed, though he said he'd have to recommend it as it's standard, as said my NEW MO.  I finally consulted Dr. Michael Lagios (you can Goodle him) the DCIS and DCISMI expert pathologist.  He imports your slides from biopsy and surgery, re-examines them, consults with you by phone, sends them back, etc.  He concurred that SNB wasn't necessary, put my chance of nodal involvement at less than 1% (the other docs had put it at less than 5%, which is one in twenty), though not 0.  Provided study reporting that treated microinvasion basically never results in higher recurrence than DCIS, and also not distant recurrence.  So I didn't do it.  I'm OK with that, but sometimes do wonder.  By the way, he found a second, smaller micro (apparently, 2 micros, unconnected, are not worse than one) in my core biopsy that the HMO had said was not a micro.  Not to scare anyone, but it does make me wonder how many women who think they have not had a tiny micro really have.

Jezzabelle, in addition to the very odd way that this all developed for you, here are a couple of other strange things that stand out to me in what you've described.

You say that the description of your tumor is a "focus of microinvasive ductal carcinoma arising in a background of
intermediate grade DCIS with associated necrosis and
microcalcifications."  But you also indicate that you've been staged as Stage I, "(T1(a), N0,M0) invasive ductal carcinoma".  A true microinvasion (a lesion of 1mm in size or smaller) is not a T1a tumor, it's a T1mic tumor.  And while the staging is Stage I, it's usually described as DCIS-Mi.  So your TNM status and the use of the description "invasive ductal carcinoma" seems to suggest an area of invasion that is slightly larger than a microinvasion.  In the scheme of things, 2mm (for example) doesn't make much difference vs. 1mm, but you might want to get this clarified, particularly since it might impact your decision on the sentinel node biopsy.

Secondly, even with a 1mm invasive tumor (and certainly with an T1a tumor), the pathologist should be able to determine grading and hormone status (and HER2 status particularly if the tumor is a T1a tumor).  So the fact that you've been told that they can't provide this info is really odd - and again this could impact your decision on the sentinel node biopsy.

As for the SNB itself, don't worry about the fact that the tumor has been removed.  Often the injections are made around the nipple rather than at the tumor site, so the fact that you've had the lumpectomy shouldn't impact the reliability of the SNB. 

So sorry that you find yourself in this very confusing situation!

Jezzabelle, thanks for that clarification.  

If the report says that the microinvasion measures considerably less than 1mm in greatest dimension, that's really good news and that explains why grade and hormone testing can't be done.  It appears simply that your surgeon isn't completely up-to-speed on staging.  An invasive lesion of that size is a T1mic tumor, and your diagnosis would usually be called Stage I DCIS-Mi (although technically IDC is correct).  You might want to clarify that with your MO, who I hope would be more familiar with staging protocol.

Here is an explanation of staging, from the official source: Breast Cancer Staging: Working With the Sixth Edition of the AJCC Cancer Staging Manual

A few of the key points relevant to this discussion:

T1mic      Microinvasion ≤0.1 cm in greatest dimension

T1a          Tumor >0.1 cm but ≤0.5 cm in greatest dimension  

- The pathologic tumor size for classification is a measurement of only the invasive component.

- When there are multiple foci of microinvasion (extension of cancer cells
beyond the basement membrane into the adjacent tissues with no focus
greater than 1 mm in greatest dimension), the size of only the largest
focus is used to classify the microinvasion. (Do not use the sum of all
the individual foci.)

And from the most recent (7th edition) update: AJCC CANCER STAGING MANUAL SUMMARY OF CHANGES FROM THE SIXTH EDITION TO THE SEVENTH

- Made specific recommendations that (1) the microscopic measurement is the most accurate and preferred method to determine pT with a small invasive cancer that can be entirely submitted in one paraffin block...

- Made the specific recommendation to estimate the size of invasive cancers that are unapparent to any clinical modalities or gross pathologic examination by carefully measuring and recording the relative positions of tissue samples submitted for microscopic evaluation and determining which contain tumor

- Acknowledged that the prognosis of microinvasive carcinoma is generally thought to be quite favorable, although the clinical impact of multifocal microinvasive disease is not well understood at this time.

I added my radiation treatment to my stats, but I see that they are still not showing up. 

TB- go back to your edit on your profile and make sure its "public"  when you edit it does not default to being public until you change it. 

So here is my interesting story- I got interested when reading all the great info Beesie had here around staging and pathology and decided to pull out my report.  Imagine my surprise when I re-read and realized that not only did I have a .8cm invasive carcinoma but I also had DCIS with aggregates to 1.3cm- imagine that.  I don't know if I just did not read it closely, spaced it or what.  

I do remember getting my pathology report and my surgeon giving it to me and saying "you can read this probably better than I can so I will just give it to you"  I guess I really didn't read it as well as she thought I could. Low nuclear grade and clear margins to .6cm to the posterior margin-  Glad to have this board and people like Beesie constantly putting out very good information in detail.