What is next for IDC mastectomy with no sentinal node biopsy.

LJDH, you have DCIS not IDC (as you show in the pathology report). There is a big difference. You can't do a sentinel node biopsy once the DCIS/breast is removed. Your surgeon should be sending you to an oncologist who will go over any treatment options. They don't normally do an oncotype test with DCIS as DCIS stays in the ducts. 1mm invasion could have been from the surgery or biopsy; VERY, VERY tiny. I only had an MRI of my breasts before surgery and not my full body. You should have a good talk with your oncologist about what to watch for with any symptoms in the future, or, as I did, read these threads. They are a wealth of information and there is an answer to ANY question you may have. Good luck on your journey!!

LJDH, I'm sorry you find yourself in this situation.

Usually an SNB is done when a MX is done for DCIS, just as a precaution in case some invasive cancer shows up.  But the likelihood of finding any invasive cancer when the amount of DCIS is estimated to be only a few mm in size is extremely low, so I understand why you didn't have the SNB.  May I ask, with such as small estimated area of DCIS, why did you choose to have the MX?

Now that it turns out that you do have a microinvasion of IDC and you've had the MX, your situation becomes more complicated.  My microinvasion was found during my excisional biopsy so I knew going into my MX that I was Stage I and not Stage 0 and I needed to have my nodes checked.  My surgeon told me that the risk of nodal invasion for someone with a tiny invasive cancer, such as a microinvasion, is about 10%.  I've seen some studies since then that put the confirm that, with a range of nodal involvement (depending on the study) from 6% to over 20%.  So the risk is low, but there is a risk.  

Microinvasive Breast Cancer and the Role of Sentinel Node Biopsy: An Institutional Experience and Review of the Literature  

Sentinel Lymph Node Biopsy in Intraductal Carcinoma of the Breast with Microinvasion

There are some ways to do an SNB after a MX, although it's very unusual for surgeons to try these different approaches - which is why you usually hear that an SNB after a MX "can't be done".  That's not entirely true, but it's certainly very difficult and most unusual to do an SNB after a MX.  Recently there was some discussion about this in the following thread:  Topic: LCIS- Sentinel node biopsy- To do or not to do?  Although the thread is in the LCIS forum, you may find the discussion about SNBs after a MX helpful.  And here is a study that was linked to in that discussion which might be helpful: Reoperative Sentinel Lymph Node Biopsy after Previous Mastectomy

I would suggest that you take this information to your surgeon to see whether there is any way that he can attempt an SNB.  Simply removing a few nodes without going through the SNB injection procedure is risky, because there is no way to know if the nodes removed are those into which cancer would first flow from the breast. That's why an axillary node dissection usually involves a lot more than 4 nodes.

As for the Oncotype, there are actually two Oncotype tests, one for DCIS and one for invasive cancer.  Since you have the microinvasion and you had a MX, the DCIS Oncotype would not be appropriate for you.  The role of that test is to determine if women who have a lumpectomy for DCIS may be low enough risk that they can skip rads.  Obviously, that's not a decision that's on your plate!

The Oncotype of IDC might be a possibility for you, although I don't that it's used often with such a small invasive tumor.  I also suspect that with an invasive tumor that is less than 1mm in size, there wouldn't be enough tissue to test.  What's important to keep in mind is that with such a small invasive cancer, normally there is no change in treatment plan from what it would be if you had pure DCIS - no chemo, etc..  Even if you had a tiny amount of nodal involvement, it's quite possible that the treatment plan wouldn't change.  That's why the Oncotype probably wouldn't be done in a situation like yours. 

As for the possibility that the 1mm of invasion might be from the biopsy or surgery, that's actually not the case.  A surgical procedure cannot turn DCIS into invasive cancer.  And I would suspect that the appearance of a microinvasion would be quite clear under a microscope, since the cancer cells would be visible right at the edge of the duct where they would have broken through, as these pictures from BC.org show:  Image - Range of Ductal Carcinoma in situ

Talk some more to your oncologist and surgeon to see what options they can present to get your nodes checked.  With such a very tiny amount of invasive cancer, it's unlikely that there will be nodal involvement, but it is something that normally should be checked.