In this paper, we present the very first virtual reality training system for neurosurgical interventions based on a real surgical microscope and on a haptic interface for a better visual and ergonomic realism. Its main purpose is the realistic simulation of the palpation of low-grade glioma. The ability of a surgeon to feel the difference in consistency between tumors cells and normal brain parenchyma requires considerable experience and it is a key factor for a successful intervention. The simulation takes advantage of an accurate tissue modeling, a force feedback device and the rendering of the virtual scene directly to the oculars of the operating microscope.