Breast masses with peripheral rim enhancement on dynamic contrast-enhanced MR images: Correlation of MR findings with histologic features and expression of growth factors

PURPOSE: To investigate the histologic bases of rim enhancement of breast masses demonstrated on dynamic contrast material-enhanced magnetic resonance (MR) Images. MATERIALS AND METHODS: Dynamic MR images of breast lesions (invasive carcinoma, n = 29; other, n = 6) in 35 women were reviewed. In each patient, subtraction images of the dynamic contrast-enhanced study were obtained, and early and delayed rim enhancement and delayed internal enhancement were evaluated. The MR findings were correlated with the ratio of microvessel density of the peripheral to the central portion of the lesion, fibrosis, and other histologic features, including expression of vascular endothelial growth factor (VECF) and transforming growth factor beta1. RESULTS: Early rim enhancement was observed in 29% and delayed rim enhancement was noted in 60% of all patients. Small cancer nests, a high ratio of peripheral-to-central microvessel density, peripheral VEGF expression, and a low ratio of peripheral-to-central fibrosis were correlated with early rim enhancement. Delayed rim enhancement was correlated with a high degree of fibrosis and inflammatory changes. Delayed internal enhancement was correlated with a high degree of fibrosis. CONCLUSION: Rim enhancement of breast lesions at MR imaging is due to a combination of angiogenesis, distribution and degree of fibrosis, expression pattern of VEGF, and various histologic features.