In this paper we present a novel approach to track and explore stiff tissues within 3-D ultrasound volumes acquired by a medical 3-D ultrasound probe mounted on a six degrees of freedom robotic arm. Autonomous palpation and on-line elastography process are implemented to estimate the elastic property of the tissues (strain) in a volume of interest (VoI) indicated by the user. The compression motion, required for the elastography, is performed by controlling the force applied by the ultrasound probe to the tissues. A visual servoing control for centering a rigid tissue (target) inside the field of view (FoV) of the ultrasound probe is established to always maintain the target visible. Additionally, rotations around the contact point between the tissue and the ultrasound probe are teleoperated through a haptic device handled by the user in order to allow exploration of the target surrounding areas. Results show a stable system that can be used in the future for diagnosis of diseases or tumor location.