Fat Necrosis of the Breast: Magnetic Resonance Imaging Characteristics and Pathologic Correlation

Rationale and Objectives: This study aims to describe the magnetic resonance imaging (MRI) features of fat necrosis on magnetic resonance mammography, which may downstage a suspicious lesion to a merely benign finding. Materials and Methods: This prospective study included 82 female patients (mean age 50 years) who were diagnosed to have suspicious lesions by mammography, ultrasonography or both. All patients underwent MRI including diffusion -weighted imaging and spectroscopy. Image postprocessing and analysis included signal intensity, enhancement characteristics, diffusion restriction, and spectroscopic analysis. All patients underwent histopathological analysis for confirmation. Sensitivity, specificity, positive predictive value (PPV), and negative (NPV) predictive value were calculated. Results: To label a lesion as fat necrosis on MRI analysis, presence of fat signal in a lesion revealed sensitivity of 98.04%, specificity of 100%, PPV of 100%, and NPP of 96.88%, whereas nonenhancement of the lesion itself revealed sensitivity of 96.08%, specificity of 100%, PPV of 100%, and NPP of 93.94%. However, adding both the nonrestriction on diffusion analysis and the lack of tCholine at 3.22 ppm increased the sensitivity and specificity to 100%, as well as PPV of 100% for fat necrosis and hence a NPV for malignancy of 100%. Conclusions: MRI proved to be of value in differentiating fat necrosis from malignancy based on the molecular composition of fat necrosis, clearly depicted by MRI without the need for invasive confirmation by biopsy.