In haptic augmented reality (AR), a stimulus from a real object is augmented by a synthetic haptic signal. We previously developed a haptic AR system wherein the stiffness of a real object can be augmented with the aid of a haptic interface. This demonstration presents a case study of this technology for medical training of breast cancer palpation. A real breast model made of soft silicone is augmented with a virtual tumor rendered inside. Haptic stimuli for the virtual tumor are generated based on a contact dynamics model identified via real measurements. With our palpation system, a user can experience excellent realism comparable to that of a real breast mock-up containing a real tumor.