Chordoma is a rare malignant
tumor that arises from notochord remnants. Chordomas account for 1 to
4% of all bone tumors.l They occur in older adults with the highest prevalence
in the fifth to seventh decade. The ratio of male to female is two to
one. Due to their origin in the notochord, chordomas occur in the mid-line
of the axial skeleton. One half of cases occur in the sacrococcygeal region
and one third occur at the base of the skull. Other rare sites include
transverse processes of vertebrae and the paranasal sinuses.
The clinical presentation depends on the location of the tumor. Sacrococcygeal
tumors often present as low back pain with no characteristic pattern or
time course. Sacrococcygeal tumors can also present as bowel and bladder
dysfunction. Presacral tumors can sometimes be palpated on rectal exam.
Sacral tumors are often large at presentation as a large volume of tumor
can be accommodated within the pelvis. Anterior cervical tumors can present
as dysphagia and posterior cervical tumors can cause neurological deficits.
Tumors at the base of the skull may present with headaches.
On plain x-ray, chordomas appear as a solitary mid-line lesion with bony
destruction. There is often an accompanying soft tissue mass. Approximately
half of the time focal calcifications are present. CT and MRI scans help
demonstrate the soft tissue component, calcifications and epidural extension.
MRI is helpful in identifying local recurrences. Chordomas have reduced
uptake on bone scan.
On gross examination, chordomas are soft, blue-gray, lobulated tumors.
There are gelatinous translucent areas and often a capsule is present.
The lesion often tracks along nerve roots in the sacral plexus or out
the sciatic notch in planes of least resistance.
Under the microscope, the chordomas are characterized by lobules and fibrous
septa. The malignant cell has eosinophilic cytoplasm. Prominent vacuoles
of mucus push the nuclei to the side resulting in "physaliphorous"
cells from the Greek word for bubble or drop.
During the fourth to sixth week of fetal development mesenchymal cells
from individual sclerotomes merge to surround the notochord and form the
vertebral bodies. The notochord normally degenerates and remnants form
the nucleus pulposus of the vertebral disc. The prevailing theory is that
in chordomas the notochord fails to degenerate and then undergoes malignant
transformation. The major failing of this theory is that normal notochord
remnants have never been observed.
The treatment of chordomas is difficult. Wide surgical excision is desirable
but rarely feasible based on the anatomic location of the tumor. With
sacrococcygeal tumors, sexual function and sphincter control may be compromised
after surgery. Radiation is used if complete resection is impossible.
Chordomas metastasize to lymph nodes, lungs, liver and bone. Chemotherapy
can be used for late stage disease.
l Healey, JH and JM Lane, Chordoma: A Critical Review of Diagnosis
and Treatment, Orthopedic Clinics of North America, 20(3):417-425,
Bullough, Peter, Orthopaedic Pathologv (third edition), Times Mirror
International Publishers Limited, London, 1997.
Huvos, Andrew, Bone Tumors: Diagnosis. Treatment and Prognosis,
W.B. Saunders. Co., 1991.
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