Background: B3 category mainly consists of lesions that provide benign histology on core biopsy, but either are known to show heterogeneity or have increased risk of associated malignancy. However, the level of risk is very different for different entities. All the cases should be looked for atypia. The objective of this study is to compare various B3 lesions in two audits, to calculate the median rate and upgrade rates (the rate at which they turn into malignancy on subsequent excision) for different B3 lesions and to compare them with the national standards and published literature. The study aims to see whether vacuum assisted excision or surgical excision has been done in such lesions. Methods: This is a retrospective study and encompasses two audits done in 2017- 18 and 2020-21 at Queen's hospital, Barking, Havering and Redbridge NHS trust. A total of 4478 cases were reviewed and 206 cases were graded as B3 on core biopsy. Results: Overall, 113 cases were graded as B3 in 2020-21 and 93 cases in 2017- 18 giving the median rate of 5% and the overall upgrade rate of 12%. Intraductal papilloma was the most commonly seen lesion in both audits. Also, 31 cases underwent vacuum assisted excision and 62 cases underwent surgical excision, with 38 cases not undergoing further excision. Conclusion: The median rate was within the 'preferred median rate'- 4.5-8.5% and the upgrade rate was comparable (16.57%) with those of National Breast Cancer screening audit, 2016-2019. The type of excision for various lesions was in line with the criteria stated by the Royal College of Pathologists. The lesions which were not excised did not turn into malignancy on follow-up. [ABSTRACT FROM AUTHOR]