In neurofibromas type I (plexiform) and type II (diffuse) the Schwann cell is the predominant cell in the neoplastic proliferation. Electron microscopic investigation of a neurofibroma with structures resembling tactile corpuscles (type III) revealed neoplastic proliferation of perineurial in stead of Schwann cells. The tactile-like (pseudo-Meissnerian) corpuscles (corpuscles neurofibromateux) are formed by neoplastic perineurial cells. These cells have a tendency to wrap themselves around longitudinal structures, such as collagen fibres or axons, and to come into direct contact with the latter. The close relationship between the axon and the neoplastic perineurial cell, analogous to that between axon and Schwann cell, points to a neuroectodermal origin origin of the perineurial cell. The electron microscopic appearances suggest that either the Schwann cell or the perineurial cell is the essential neoplastic component of neurofibromas, the fibroblastic proliferation being a secondary phenomenon.