Background

Breast cancer is the leading cancer in women worldwide, with an estimated 318,000 new cases of breast cancer expected to be diagnosed in the U.S. in 2017. When discovered at an early stage the standard surgical treatment is lumpectomy, in which the tumour is removed from the breast while sparing as much healthy tissue as possible. While long-term survival rates are equivalent to mastectomy, many women prefer lumpectomy because it results in a better cosmetic outcome.

However, many tumours are not palpable and so surgeons have limited or no direct visual or tactile feedback to ensure that the entire tumour is included in the excised tissue. As a result, it is common practice for the excised tissue to undergo