Whether to do Sentinel Node Biopsy

My sister is 50 yrs. old and was diagnosed with DCIS  which is high grade with necrosis. 9 millimeter calcification. Would it be recommended to do a sentinel node biopsy with an expert in that area at the same time a lumpectomy is done???There is no sign of invasion at this time on MRI etc., but we understand that could be different once lumpectomy is done and pathology comes back.  Two Doctors said it is unnecessary to do at time of lumpectomy but one who is an expert in SNbiopsy said it would be good to do at same time, in case it turns out there are microinvasions, she won't have to go back in for another surgery to do SNbiopsy which carries virtuall no downside. Would it be recommended with this kind of DCIS which is high grade and has necrosis in light of small risk of lymphodema etc. from sentinel node biopsy --and what are risks from Sentinel node biopsies?  Thank you!!!

[luna1]

My sister had a lumpectomy and the MRI did not show any node involvement. But they did a sentinal node biopsy during the lumpectomy and did find the node had a significant amount of cancer in it . So they did take out a few more nodes (level 1) and also found a few more with cancer. Some doctors thought they should of taken more nodes but my sister did not want the risk of lymphodema.
so far her arm is fine .