multiple lesion excisions

I am having denials from Medicare for multiple (3) lesion excisions. Each excision was coded with CPT 11641. Medicare denied for invalid # of units. Initially it was filed on 3 separate lines with modifier 76 on the last 2 lines. We then refiled on one line with 3 units. Each time, Medicare denied for invalid # of units and we were told when we called that Medicare will only allow 2 excisions at a time. Has anyone else experienced denials from Medicare for this reason and what did you do? We can't control the number of lesions a patient needs to have removed so this just doesn't seem right to me. Thanks in advance for any advice!

multiple lesion excisions