It looks to me like the insurance company may think that the 13101 code was for the left breast, as a wound repair/closure code, after the revision was done(which would bundle), but it was actually for a dog ear on the BACK of the patient. Separate area, separate incision, therefore the 59 modifier is allowed, and NCCI edits on the 13101 show this to be the case. I would contact insurance, explain this to them, and see if they won't adjust the claim. If not, you should appeal with the op report.