Definition
Chordoma, A rare solitary slowly growing neoplasm of
skeletal tissue in adults, derived from persistent portions of the
notochord; composed of cells arranged in lobules, with abundant
quantities of extracellular mucus; some cells contain vacuoles of
mucus that resemble soap bubbles.
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Radiographic Appearance
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.
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Pathology
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 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.
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Treatment:
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. |
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