Brief fixation does not hamper the reliability of Ki67 analysis in breast cancer core-needle biopsies: A double-centre study

Aims: Immunohistochemical assessment of Ki67 expression in core-needle biopsies (CNBs) is increasingly playing a role in therapeutic decision-making for breast cancer patients. Within the framework of same-day diagnosis of breast lesions, fixation times are markedly decreased. We therefore attempted to validate Ki67 analysis in briefly fixed breast cancer CNBs. Methods and results: CNBs of 136 consecutive patients with invasive breast cancer diagnosed through the same-day diagnosis programme of both the University Medical Centre Utrecht (UMCU) and the Radboud University Medical Centre (RUMC) were included. CNBs were fixed in formaldehyde for approximately 45 min at the UMCU and for between 60 and 90 min at the RUMC. Immunohistochemistry for Ki67 expression was compared between the briefly fixed CNBs and conventionally fixed resection specimens of the same tumour. The overall agreement between CNBs and resections was 122 of 142 (85.9%) (κ = 0.71; 95% CI 0.60-0.83). Positive and negative predictive values were 79.7% (95% CI 67-88%) and 91.0% (95% CI 82-96%), respectively. Conclusions: Overall agreement for Ki67 expression was good between briefly fixed CNBs and conventionally fixed resection specimens, and within the range of studies comparing conventionally fixed CNBs and resections.