Rim-enhancing breast masses with smooth or spiculated margins on magnetic resonance imaging: histopathology and clinical significance.

Rim enhancement is defined as enhancement that is more pronounced at the periphery of a mass. It can have varying appearances, ranging from a thin pattern to one that is thicker. This internal enhancement characteristic is an established characteristic of malignant lesions. Additionally, the use of combined descriptors, especially internal enhancement characteristics and the associated margin, can provide a more powerful predictive value than that of individual descriptors. The margin assessment of rim-enhancing masses is important and can vary in appearance from smooth to spiculated. Moreover, rim enhancement may be dynamic in that it changes appearance during the dynamic phases of contrast- enhanced breast magnetic resonance imaging (ce-MRI), and this feature can lead to confusion in the correct application of this lexicon. Rim-enhancing masses on ce-MRI are typically of two morphological types (i.e., a thin rim-enhancing mass with a smooth margin and a thick rim-enhancing mass with a spiculated margin). It is helpful to review and clarify the lexicon of rim enhancement using combined descriptors based on the pathological findings as doing so can help predict the likelihood of malignancy of ce-MRI lesions.