MKI67 and breast carcinoma: Although the definition of high-risk breast cancer continues to evolve, key features associated with a high risk of breast cancer recurrence include: younger age at initial diagnosis [5,6,7,8], premenopausal status [5], Ki-67 ≥ 20% [9], tumour size ≥ 5 cm (T3) or tumour of any size with direct extension to chest wall, skin, or both (T4a-d) [9], high tumour grade (3) [9], and nodal involvement [9].