Reliability of Ki67-Labeling Index in Core Needle Biopsy Specimens of ER+/HER2- Breast Cancers.

The reliability of Ki67-labeling index (LI) in core needle biopsy (CNB) of ER+/HER2- invasive breast carcinoma (IBC) and factors affecting the discordance of Ki67-LI between CNB and surgical resection (SR) remain unsolved. We aimed to elucidate factors influencing the discordance of Ki67-LI between CNB and SR to classify ER+/HER2- IBC into luminal A-like (LumA) and luminal B-like (LumB). The cohort included 326 ER+/HER2- IBCs available with Ki67-LI data at both CNB and SR specimens.