Chordoma

rare neoplasm derived from remnants of the primitive notochord. They are usually located at the ends of the neuraxis, 50% in the sacral region, 30% in the sphenoccipital region and the remainder in the vertebral column with a decreasing frequency from the cervical to the lumbar and finally to the thoracic segments. They account for about 15% of primary bone neoplasms.

They most commonly occur in the sixth decade but they may present at any age, and are twice as common in males as in females.

Intracranially they account for 0.2% of all tumours and are almost all found in relation to the clivus, although rare lesions may be found exclusively in the pituitary fossa or laterally in the petrous bone. In the sacral region they are the most common primary neoplasm.

Clinical presentation is related to local invasivity. Lesions of the body of the clivus can extend ventrally and present as a parapharyngeal mass, or extend dorsally and cause cranial nerve palsies, brain stem compression or hydrocephalus. Chordomas of the sella or parasellar region present with visual disturbances, pituitary insufficiency or cavernous sinus syndrome. Lateral clival chordomas may present as a mass in the cerebellopontine angle.

Sacral tumours may present with pain, weakness and incontinence.

Pathologically they form soft, lobulated, grey masses that are histologically benign but locally invasive and destructive. Thick strands of fibrous connective tissue can give the mass a "lobular" appearance. Microscopically they are composed of clear cells with large intracytoplasmic vacuoles.

Imaging

Both CT and MR may clearly depict the lesion. CT better demonstrates the destructive effect on the bone and may depict the intralesional calcifications described in 3070% of cases (Fig.1). MR shows an inhomogeneous mass which is characteristically mostly isointense (75%) or hypointense (25%) on T1-weighted MRI sequences and moderately to extremely hyperintense on T2-weighted sequences. Septations composed of fibrous connective tissue form low-intensity strands separating lobulated areas of high intensity of T2-weighted images. Enhancement following contrast administration varies from little to striking.

Major differential diagnoses of chordoma are, respectively, in the clivus the other central skull base masses including nasopharyngeal malignancy (e.g. squamous cell carcinoma), distant bone metastasis, meningiomas, osteomyelitis (including Gradenigo's syndrome), myeloma and histiocytosis, in the sacral region giant cell tumour and metastasis from occult primary neoplasms such as renal cell or thyroid carcinomas.