['To assess whether the size of peritumoural stiffness (PTS) on shear-wave elastography (SWE) for small primary breast cancers (≤15\xa0mm) was associated with size discrepancies between grey-scale ultrasound (GSUS) and final histological size and whether the addition of PTS size to GSUS size might result in more accurate tumour size estimation when compared to final histological size.', 'A retrospective analysis of 86 consecutive patients between August 2011 and February 2013 who underwent breast-conserving surgery for tumours of size ≤15\xa0mm at ultrasound was carried out. The size of PTS stiffness was compared to mean GSUS size, mean histological size, and the extent of size discrepancy between GSUS and histology. PTS size and GSUS were combined and compared to the final histological size.', 'PTS of >3\xa0mm was associated with a larger mean final histological size (16 versus 11.3\xa0mm, p\xa0<\xa00.001). PTS size of >3\xa0mm was associated with a higher frequency of underestimation of final histological size by GSUS of >5\xa0mm (63% versus 18%, p\xa0<\xa00.001). The combination of PTS and GSUS size led to accurate estimation of the final histological size (p\xa0=\xa00.03). The size of PTS was not associated with margin involvement (p\xa0=\xa00.27).'] Does shear-wave elastography contribute to accurate tumour size estimation when assessing small breast cancers?