We report and discuss clinical breast imaging results obtained with operator independent ultrasound tomography. A series of in-vivo experiments were carried out using a recently upgraded clinical prototype based on the principles of ultrasound tomography. The in-vivo performance of the prototype was assessed by imaging patients at the Karmanos Cancer Institute. Our techniques successfully demonstrated in-vivo tomographic imaging of breast architecture in both reflection and transmission imaging modes. Masses as small as 6 mm in size were detected. These initial results indicate that operator-independent whole-breast imaging and the detection of cancerous breast masses are feasible using ultrasound tomography techniques. This approach has the potential to provide a low cost, non-invasive, and non-ionizing means of evaluating breast masses. Future work will concentrate on extending these results to larger trials.