[Pathology of myxoid bone tumors of the skull base].

Myxoid bone tumors of the skull encompass chordomas and chondrosarcomas. Their accurate diagnosis is usually a challenge and it is of utmost importance to identify chordomas because of the poorer prognosis. Even if the topography of the tumor is suggestive (median versus lateral), modern imaging is not specific enough and the diagnosis is based on histological features. We report nine cases of myxoid bone tumors of the skull including four chordomas, one chondroid chordoma and four chondrosarcomas. Smears are useful for rapid intraoperative diagnosis. Chondrosarcomas show cords of small round cells in a myxoid background while chordomas are made of multilayered sheets of larger, often vacuolated cells. Histology shows areas of cartilaginous matrix associated with myxoid areas in chondrosarcomas and in chondroid chordomas. Immunohistochemistry is determinant showing the expression of epithelial markers and Tau protein in chordomas only.