Mammograms are notoriously unreliable in pre-menopausal women. I've had numerous false positives, and more importantly I had a false negative -- lucky for me that my female family physician listened to my concerns about the lump that didn't go away, and sent me for a needle biopsy which proved positive.  I'm here to tell the tale 25 years later. Thank you to that excellent family physician, and to the cancer experts at Women's College Hospital.  Listen to your body, especially if you 'feel' that something isn't quite right.