Pre-operative ultrasound for breast tumour measurements: is there potential for mismanagement?

The pre-operative size of breast tumour is the most important factor in determining feasibility of breast conserving surgery in operable breast cancer. Currently there is no consensus on the most accurate modality to measure tumour size. A prospective study of consecutive and unselected symptomatic patients with invasive breast cancer who had primary surgery between January 2006 and December 2007 was conducted. Patients with multi-focal and multi-centric tumours were excluded. The aim of this study was to find the correlation between histological size of invasive breast cancer and pre-operative tumour size as measured by ultrasound. Over this two year period, data for 192 patients was analysed for this study. The mean tumour diameter on ultrasound and histology was 19.5mm and 29mm respectively. The difference between the means in the two modalities was found to be statistically significant (P<0.001).Ultrasound underestimates the true size of breast tumours as determined histologically. Inaccurate tumour size measurements may result in re-operations to achieve adequate margins.