Hunt KN, et al. - In this investigation, researchers prospectively compared the size of invasive breast cancer before and after neoadjuvant chemotherapy (NAC) at breast MRI and molecular breast imaging (MBI) and evaluated the accuracy of post-NAC MBI and MRI relative to pathologic analysis. To compare the longest dimension before and after NAC at MRI and MBI, women with invasive breast cancer greater than or equal to 1.5 cm were enlisted. In 72.3% of cases before NAC and 70.1% of cases after NAC, the longest dimension at MRI was within 1.0 cm of that at MBI. Before NAC, breast MRI and MBI exhibited comparable disease extent. In patients with a contraindication to breast MRI, MBI may be an alternative to breast MRI. None of the modalities showed adequate precision after NAC in predicting complete response to breast pathology to obviate tissue diagnosis to evaluate residual invasive disease. Defining the extent of residual disease compared to pathological assessment for both breast MRI and MBI was also limited after NAC.