1Molecular Imaging and Pharmacokinetics, National Cancer Center, 2Breast and Endocrine Surgery, Kumamoto University
【Background】 Tumor stiffness is mainly regulated by interactions among tumor cells, stromal cells, and extracellular matrix and was regarded as a representative feature of tumor microenvironment. Basic research has revealed that the tumor stiffness can contribute to tumor progression; however, little is known about its clinical significance because no useful modality is available in the clinical setting, thus far. The aim of this study was to explore the clinical significance of breast tumor stiffness based on ultrasound elastographic evaluation. 【Methods】 We investigated the tumor stiffness by strain elastography in 503 patients with invasive breast cancer. Correlations between strain ratio（fat lesion ratio）and clinicopathological factors and stromal-related genes’expressions in primary breast tumor, were statistically examined. 【Results】 Tumor stiffness significantly correlated with the frequency of axillary lymph node metastasis and large tumor size but not with ER expressions, HER2 status, and ki67 labeling index by analyses of both categorical and continuous variables of strain ratio. On multivariate analyses for factors influencing primary tumor stiffness, axillary lymph node metastasis was an independent factor. In the gene expression analyses, relatively hard tumors had a significantly high gene expression of lysyl oxidase but not osteopontin. 【Conclusions】 This study indicated a close relationship between primary tumor stiffness by ultrasound elastography and axillary lymph node metastasis. Tumor stiffness may have clinical significance for certain patients with breast cancer.