Strain elastography features in invasive breast cancer: relationship between stiffness and pathological factors

Our study aimed to investigate the relationship between stiffness and pathological factors in invasive breast cancer. We evaluated stiffness by strain elastography indicators of elasticity score and hardness percentage (HP) in tumors that histologically confirmed as invasive breast cancers. The relationship between stiffness and pathological factors including histologic type, histologic grade and molecular subtypes were analyzed, and the most influential factor was further determined by logistic regression analysis. Of 291 invasive breast cancers, 230 (79.0%) tumors were stiff according to elasticity score evaluation, and the average value of HP was (82.32 +/- 15.72)%. Based on the elasticity score result, the cutoff value of HP for hard tumors was 80.0% (sensitivity 90.1%, specificity 100.0%), lesions with inconsistent evaluation results by two indicators were almost grade III tumors (19/21). Differences in stiffness could be found in histologic grades (both P < 0.001) and molecular subtypes (score P=0.003, HP P < 0.001) but were not obvious in histological types (score P=0.034, HP P=0.131). Grade I or grade II (low grade) type tumors and luminal A type tumors were harder, while histologic grade was the only independent factor for tumor stiffness. The grade III group, which had a mean value of HP (65.68 +/- 18.02)%, was significantly softer than the low grade group (P < 0.001). The cutoff value of HP for low grade tumors was 80.59% (sensitivity 88.2%, specificity 84.4%). Our study revealed a close relationship between tumor stiffness and the histologic grade of invasive breast cancer. Strain elastography may have potential applications to provide prognostic information for patients with breast cancer noninvasively.