Laboratory validation studies in Ki-67 digital image analysis of breast carcinoma: a pathway to routine quality assurance.

Ki-67 proliferative index (PI) has prognostic and predictive value in invasive breast carcinoma (IBC), but clinical uptake has been hampered by suboptimal accuracy, reproducibility and standardisation. Published guidelines have addressed pre-analytical and analytical factors to improve Ki-67 PI utility; however, practicalities of ongoing monitoring of Ki-67 PI quality in IBC reporting have not been established. We aimed to evaluate the internal and external quality of our established digital Ki-67 PI IBC reporting practice at a tertiary institution.