COCCYGEAL CHORDOMA WITH FOCAL CHONDROID FEATURES
Chordoma is an uncommon malignant tumor of bone thought to originate in
notochordal remnants. It arises almost exclusively in the midline and occurs
most commonly in the sacrococcyx,
cervical spine, and clivus. Embryologically, the anatomy and development of
the notochord involves numerous complicated infoldings of this structure at the
cranial and caudal ends of the neuraxis, which may explain why notochordal
remnants tend to remain at these points and potentially give rise to tumors,
while the intervening notochord segments involute. Prognosis of the lesion is
dependent on the surgical resectability of the tumor; obviously, chordomas of
the clivus, being in a relatively inaccessible anatomical location and
surrounded by vital structures, has a poorer overall outcome when compared to a
sacrococcygeal lesion. Death usually occurs secondary to uncontrolled local
growth of the neoplasm; metastatic spread of chordoma can occur but is seldom
the primary cause of mortality.
Chordoma is characterized grossly by a soft, lobulated, firm grey to white tumor which can have a mucoid appearance. Histologically, the lesion consists of multiple lobules of small round tumor cells separated by a myxomatous stroma. The cells often display cordlike patterns of growth and have prominent vacuolation of the cytoplasm, imparting a bubbly appearance on low power examination. The cells with this characteristic have been termed "physaliphorous" and are distinctive for this neoplasm. Positive immunostaining for cytokeratins, EMA, and S100 are typical. Cytogenetic studies of this neoplasm have noted several karyotypic abnormalities, but no characteristic and reproducible findings have been reported to date. Occasionally, areas of chondroid differentation can be seen in some chordomas. Some investigators have linked such differentiation to a poorer overall outcome; some have postulated that these lesions represent a borderline lesion between chordoma and myxoid chondrosarcoma.
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Contributed by Kevin D. Horn, M.D.