5th mammogram and finding focal asymmetry

I have had 4 previous mammograms in the last 6 years. I recently had my 5th one come back with focal asymmetry on 2 views in my left breast. The machine used is the newer 3d type. My concern is, that this is the first time a mammogram came back "abnormal". I've read the statistics that 9 in 10 call backs are benign, but I'm a still a bit anxious. Is it more likely cancer since it just now showed up? Has anyone had the same thing before?