Reasons for the 17% of 630 patients who were not diagnosed by needle biopsy were as follows: inability to cooperate (1%); small or superficial lesion less than 1 cm that technically was easier to excise in the office (4%); bloody discharge without clinical or mammographic mass (1%); lesion adjacent to implant (.5%); a mammographic lesion that was too posterior, too superficial, or too faint to be performed stereotactically (5%); or patient preference (5%).