Breast DWI has shown great potential to become a contrast-free diagnostic tool for breast cancer. The purpose of this work was to determine a unified model to describe the diffusion signal of cancer and healthy breast tissues, and compare tumor conspicuity of model components to DCE-MRI and DWI estimates. Multi-exponential models with fixed ADCs were determined and the weights of each component estimated. Tumor conspicuity, defined as contrast-to-noise ratio, was found to be ~3 times higher in DCE-MRI than in the weights of multi-exponential components. This model may increase the sensitivity and specificity of DWI for breast cancer diagnosis.