In 2011, our institution adopted the policy (in line with national guidance) not to biopsy breast masses in patients <25 years if they have benign characteristics on ultrasound. This retrospective audit was performed prior to this decision. We compare the histology result with the USS findings of all patients <25 years who had a breast mass biopsied or excised, between 2003 and 2009, with respect to Stavros criteria.