Decision-making in breast pathology reporting: the effect of clinical relevant thresholds

In breast cancer (BC) pathology reports, small differences around cut-off values can impact staging and consequently, clinical decision-making. Several pathology variables are not very exact, leaving room for interpretation by the pathologist. Therefore, the aim of this study was to investigate pathologists' decision-making around clinically relevant cut-off values.

We performed a retrospective, population-based analysis of primary invasive BC specimens using real-world data from the Dutch National Pathology Registry. Data collection included tumour diameter and oestrogen receptor (ER)/progesterone receptor (PgR) status from patients diagnosed between 2014 and 2022.

Overall, 64,099 BCs were analysed for tumour diameter. For larger tumours (>2 cm), rounding was observed to the nearest half or whole centimetre. For smaller tumours, rounding occurred only to half centimetres, while there was an avoidance of the 1.0 and 2.0 cm thresholds. For ER/PgR assessment, 74,502 BCs were analysed. In cases with low ER expression, rounding was observed at multiples of 5%. However, around the clinically relevant cut-off value of 10% in the Netherlands, pathologists tend to semiquantify the percentage of ER and/or PgR expression by also using 9% and 11%, with a trend to classify a case as just positive (10% or 11%).

Pathologists take clinical cut-off values into account in their decision-making process. For tumour size, they tend to avoid the 1.0 and 2.0 cm thresholds. For ER/PgR, they tend to categorize the tumour as positive around the threshold. Further research is needed to determine the implication of this for treatment decisions.