Had a diagnostic 3dmammo & located a 1cm asymmetry in my l breast. it was visable in the cc & mlo views. nothing seen on us but he referred me for stereotactic biopsy & it was bi-rads 4. being that it was not seen on us could it still be cancer?

You have done adequate diagnostic testing to rule out presence of cancer for the present time. These findings lead one to question why you had a mammogram in the first place as it is not indicated until you are past 40 years of age. Now that you have created a doubtful situation, you should have annual follow up Mammograms and a Physical examination of your breasts done by a physician.