Chordomas and chondrosarcomas

Abstract

Primary bone tumors of the skull base are unusual conditions, mostly chordoma and chondrosarcoma [ 51 ]. Their development sends us to the embryological period in which the axial skeleton is formed [ 25 ]. The notochord is the initial axial skeletal structure that is progressively involved by the mesodermal tissue and later on replaced by cartilaginous and bone tissues [ 25 ]. Remnants of the notochord may remain entrapped by bone [ 25, 36 ], particularly in the clivus and sacrum [ 35, 36, 63 ]. They are also encountered in the nucleus pulposus [ 63 ] or forming a rather distinct intradural clival mass that may be incidentally found at autopsy, namely, the ecchordosis physalifora [ 28 ]. Besides, focal persistent rests of fetal cartilage may remain unchanged in the skull base during ossifi cation [ 13, 51 ]. From the notochord remnants arise the chordomas [ 8, 25, 28, 36, 50, 51 ], while the persistent fetal cartilage rests may be the progenitors of the chondrosarcomas [ 13, 34, 51 ]. Other assumption is the origin of chondrosarcomas from metaplasia of meningeal fi broblasts when occurring outside the skull base [ 5 ]. Both chordomas and chondrosarcomas are rare tumors each comprising 0.1- 0.2 and 0.02-0.2 % of all intracranial tumors, respectively [ 12, 18, 63, 64 ].