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!!!

[Cleveland Clinic]

Dear risb:  There is no test, other than biopsy, that can determine whether there is any invasion in a tumor.  A needle or core biopsy takes a small sample of an area of concern and then it is hoped that this is representative of the rest of the area.  If the specimen comes back DCIS or invasive breast cancer, additional surgery (lumpectomy in many cases) will need to be done.  If we knew that the entire lump is DCIS, then sentinel lymph node biopsy is not necessary and your sister would have an unnecessary surgery.  If, on the other hand, there is any invasion in the abnormality, a sentinel lymph node biopsy would be recommended and your sister could need additional surgery.  Further, the other challenge is making sure all of the bad tissue is removed with the surgery.  If there are margins (or edges) that have bad cells, then additional surgery may be needed to fix that.  In other words, there is no magic right or wrong answer.  Most surgeons will ere on doing less to prevent unnecessary procedures but in some cases, this can result in needing more procedures.