Chordoma
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: Notochordoma; chordocarcinoma; chordoepithelioma
Overview
Chordomas are uncommon malignant tumors that account for 1% of intracranial tumors and 4% of all primary bone tumors. They originate from embryonic remnants of the primitive notochord (earliest fetal axial skeleton, extending from the Rathke's pouch to the coccyx). Since chordomas arise in bone, they are usually extradural and result in local bone destruction. They are locally aggressive, but uncommonly metastasise.
Pathophysiology
Fluid and gelatinous mucoid substance (associated with recent and old haemorrhage) and necrotic areas are found within the tumor. In some patients, calcification and sequestered bone fragments are found as well. The variety of these components may explain the signal heterogeneity observed on MRI. Incomplete delineation of the tumor and microscopic distal extension of tumor cells may explain the frequency of recurrences. Physaliphorous cells are classically seen on microscopy. Metastatic spread of chordomas is observed in 7-14% of patients and includes nodal, pulmonary, bone, cerebral or abdominal visceral involvement, predominantly from massive tumors. True malignant forms of chordomas occasionally have areas of typical chordoma and undifferentiated areas, most often suggestive of fibrosarcoma; the prognosis is poor.
Location
Chordomas are found along the axial skeleton and a relatively evenly distributed among three locations: Sacrococcygeal: 30-50% Spheno-occipital: 30-35% Vertebral body: 15-30%
Sacrococcygeal
This is the most common location, accounting for approximately 30-50% 2-3 of all chordomas and involving particularly the fourth and fifth sacral segments. In this location a male predilection has been reported (M:F ratio of 2:1) and the tumor may be particularly large at presentation. Chordoma is the most common primary malignant sacral tumor.
Spheno-occipital
The clival region is the next most common, accounting for 30-35% 2-3 of cases. Typically the mass projects in the midline posteriorly indenting the pons. This characteristic appearance has been termed the 'thumb sign". In contrast to sacrococcygeal tumours, there is currently no recognised gender difference.
Vertebral bodies
Chordomas of the vertebral bodies are rare but after lymphoproliferative tumours are nonetheless the most common primary malignancy of the spine in adults 2. They most commonly involve the cervical spine (particularly C2), followed by the lumbar spine then the thoracic spine. They often extend across the intervertebral disc space, involving more than one vertebral segment. They may extend into the epidural space, compressing the spinal cord, or along the nerve roots, enlarging the neural exit foramen.
Epidemiology
Chordomas occur at any age but are usually seen in adults (30-70 years). Those located in the spheno-occipital region most commonly occur in patients 20-40 years of age, whereas sacrococcygeal chordomas are typically seen in a slightly older age group (peak around 50 years 10). They are commonly found in Caucasians.