Pentameric last-digit preference and stage border avoidance in pathology measurement

Cancer treatment relies on accurate staging, an essential aspect of which is determination of the size of a tumour. Measuring the size of a tumour in daily practice often proves problematic and results in rounding of values to approximate values. It has been shown that size values are most frequently reported with end digits of 0 or 5.

We sought to determine whether this observation holds true in our national cancer registry of breast and lung tumours. Data from patients with breast and lung cancer were retrieved from the Netherlands National Cancer Registry and analysed for tumour size. Whereas a preference for terminal digits of 0 or 5 (pentameric preference) was clearly present for lung cancer, critical pentameric values at stage boundaries were avoided in breast cancer.

In conclusion, pathologists adopt a practical approach to tumour size measurement by rounding values and avoiding stage border boundary values, thus circumventing potential difficulties in treatment decisions.