According to this article from HealthDay, the interpretation of diagnostic (not screening) mammograms can vary, depending on the radiologist looking at them. To make sure that you get the most accurate interpretation of the results, health experts recommend that you:

• have your mammogram done at a location that has a breast-imaging specialist, or at least where the radiologist reads a significant number of mammograms a year.
• visit the same facility every time you have a mammogram, or at the very least bring your past films with you. Your radiologist needs to read the results on a continuum, or by looking at past images.
• have your mammogram done at a facility where there is more than one radiologist, so that, if necessary, consultation is possible.

Interestingly, experience doesn't seem to make a radiologist more accurate. Though experienced doctors were less likely to biopsy a false positive, they weren't as good as newer radiologists at picking up the cancer in the first place.