Stiffness of tumours measured by shear-wave elastography correlated with subtypes of breast cancer

To evaluate the correlation between stiffness values obtained by shear-wave elastography (SWE) and breast cancer subtypes. This was an institutional review board-approved retrospective study with a waiver of informed consent. The stiffness of 337 invasive breast cancers in 337 women was evaluated by SWE and mean stiffness values (kPa) and qualitative colour scores (1-5) of tumours were obtained. The results were analysed according to BI-RADS category, tumour size, grade and tumour subtype (triple-negative [TN], human epidermal growth factor receptor 2 [HER2]-positive, and oestrogen receptor [ER]-positive) using a multiple linear regression analysis. The mean stiffness values and colour scores were: 146.8 kPa +/- 57.0 and 4.1 +/- 1.1; 165.8 kPa +/- 48.5 and 4.6 +/- 0.7 for TN tumours (n = 64), 160.3 kPa +/- 56.2 and 4.3 +/- 1.0 for HER2-positive tumours (n = 55) and 136.9 kPa +/- 57.2 and 4.0 +/- 1.1 for ER-positive tumours (n = 218; P < 0.0001). All three breast cancers classified as BI-RADS category 3 on B-mode ultrasound were TN subtype. A multiple linear regression analysis revealed that tumour size, histological grade and tumour subtype were independent factors that influenced the stiffness values. High stiffness values correlated with aggressive subtypes of breast cancer. Shear-wave elastography is increasingly used to measure the stiffness of breast tumours. Triple-negative and HER2-positive tumours showed greater stiffness than ER-positive tumours. All breast cancers classified as BI-RADS 3 on B-mode ultrasound were triple-negative subtype. Tumour size, histological grade and subtype were independent factors influencing SWE stiffness.