Confused about nodes and margins

Shira

I am confused about three things (at this moment!).

If someone has positive Sentinel Nodes, and so the docs go back and take Axillary Nodes, are they taking more just to test more nodes and determine status, or are they also removing the nodes to prevent the cancer from spreading?  Also, if they take a lot of nodes, then are there any left to do their job?  Also, if the nodes are there to protect and take infection away, then what would the nodes do with any cancer cells if we didn't remove them? 

Next, I get that we want to have clear margins, but why are unclear margins such a big deal diagnostically? Doesn't it just mean that thy didn''t have the size right at first? 

Last, I had an MRI in the early part of my diagnosis.  However, it doesn't tell the lymph node status and I don't think it sized the tumor right, so does anybody know what it rules out or tells us?

Thanks, having some issues getting diagnosed, which is why I am asking!

SpecialK

I can only answer your question from my own experience.  I had a positive SNB, but it was not discovered until after my BMX in post-op pathology.  Because I was Her2+ both my MO and BS felt that I needed a complete axillary node dissection.  If you have a positive sentinel there is a much stronger possibility that more nodes have cancer.  So either you have chemo and your axilla is radiated, or you have ALND, or you roll the dice.  Knowing the total number of nodes that have cancer also affects correct staging.  Additional nodes are taken to determine how much cancer is there, and to keep it from having access to the rest of your lymphatic system, theoretically reducing the odds of distant metastasis.  There is an entire lyphatic system so there are other nodes in the body to filter infection.  Removing nodes from the axilla does put your arm at risk though, so you need to take care and minimize cuts, scrapes, insect bites, etc., on that arm because it can't do as good a job at filtering.  There are levels of nodes in the axilla, and each of us have differing numbers of nodes there.

Obtaining clear margins actually involves two scenarios - a "dirty" margin meaning there is cancer all the way to the edge of the removed tissue, which can mean residual cancer in the breast -or - too small a clear margin.  The usual standard is a minimum of 2mm all the way around the removed mass.  Approximately 20% of lumpectomies require re-excision for better margins.  Imaging estimates sizing but it is not exact.  Most surgeons only want to remove what they must while getting good margins, but they are flying blind to a certain degree - if they have to go back, they are usually only taking a few millimeters more.  Removed tumors are inked with differing colors before being sent to pathology - front, back, left, right.  This tells you exactly where the additonal tissue needs to removed from.

MRI is only another imaging tool.  All imaging gives information - my 2cm tumor did not show on mammogram, it did show on ultrasound, my MRI showed consistent sizing, but not my positive nodes.  All forms of imaging work a bit differently - mammography is not as effective on dense breasts, but MRI is supposed to be better.  Ultrasound can be useful but sometimes does not see things that mammo and MRI do.