MKI67 and breast cancer: Due to availability of the donated tissue for research purpose, BC‐4 and BC‐5 could be collected after pathological assessment of the tissue at the hospital, while BC‐1, BC‐2, and BC‐3 could only be collected the next morning and were kept in medium at 4 °C. Comparing the Ki‐67 quantification of received breast cancer tissues to the pathological assessment at the hospital, a reducing effect on proliferative activity could be observed between two donors with a similar breast cancer type, underlining the importance of a shorter time between tissue collection and processing.