TBX1 and chordoma: Skull base chordomas usually grow in the clival midline, while a lateral clival origin, in and next to the petroclival fissure, would favor chondrosarcoma.20, 23Yet, chordomas growing laterally in the petrous bone have previously been described.24As for the presented case, immunohistochemical detection of brachyury is currently required to confirm the diagnosis of chordoma.