Chordoma and chondrosarcoma of the skull base

Abstract

Chordomas are very rare, slowly growing tumours of the bone with an incidence rate of <0.1 per 100,000 per year. They represent about 1% to 4% of all primary malignant bone tumours [17]. The median age at presentation is around 60 years; however, presentation with skull base tumours may occur at a younger age and has been reported in children and adolescents [21]. Chordomas arise from embryonic remains of notochord and show a dual epithelial-mesenchymal differentiation. Its epithelial phenotype is manifested through expression of positive markers for cytokeratin (CK) and epithelial membrane antigen (EMA). They also are positive for S-100 and vimentin. After obliteration of the notochord and its displacement from the central to the cranial and caudal positions, microscopic foci may persist in the vertebral bodies at the cranial and caudal ends of the embryo. The sacrococ-cygeal bones (50%) and clivus (in 25% to 36% of cases) are the preferential sites for chordomas. Malignant transformation typically occurs between the third and fourth decade for spheno-occipital lesions and between the fifth and sixth decade for the sacrococcygeal type [14, 23]. Chordomas are lobular grey, semitranslucent tumours of varying size. They are usually soft and gelatinous, sometimes with foci of calcification. They may invade the dura to stretch cranial or spinal nerves, or displace blood vessels and the brain stem. In typical chordoma, the cells tend to be arranged in cords set in a pale matrix of mucopolysaccharide with a characteristic physaliphourous appearance (Fig. 1) [20]. Mitoses are infrequent, even in specimens from recurrent or metastasized chordomas. In chondroid chordomas, the stroma resembles hyaline cartilage with neoplastic cells in lacunae. The chondroid histology, commonly seen in the skull base, exhibits low-grade behaviour and favourable long-term outcome. Conversely, dedifferentiated chordoma is observed in < 5% of cases, has features of high grade spindle cell sarcoma and demonstrates an aggressive clinical course [3]. Clinical presentation depends on the specific sites of their extension. Pain is the main symptom followed by visual disturbances and lower cranial nerve palsies, based on the location of the lesion. Intracranial chordoma typically arises from the clivus and can invade the dura, extend in any direction, for example towards the foramen magnum, compress the brainstem or infiltrate anteriorly the cavernous sinus [16]. Among cranial nerves, the abducens nerve is the most commonly affected. Headache is usually reported in an occipital or retro-orbital location.