Diffusion-weighted imaging reflects variable cellularity and stromal density present in breast fibroadenomas ★

ObjectiveTo determine the underlying histopathologic features influencing apparent diffusion coefficient (ADC) values of breast fibroadenomas.Materials and MethodsBiopsy-proven fibroadenomas (n = 26) initially identified as suspicious on breast magnetic resonance imaging (MRI) were retrospectively evaluated. Histopathologic assessments of lesion cellularity and stromal type were compared with ADC measures on diffusion-weighted MRI.ResultsPresence of epithelial hyperplasia (increased cellularity) and dense collagenous stroma were both significantly associated with lower lesion ADC values (P = .02 and .004, respectively).ConclusionVariations in epithelial cellularity and stromal type influence breast lesion ADC values and may explain the wide range of ADC measures observed in benign fibroadenomas.