Practice Essentials
Chordoma is a relatively rare malignant midline tumor that arises in the axial skeleton, primarily at its cranial and caudal ends; it is derived from persistent embryonic notochordal cell rests. [1, 2, 3]
A resemblance exists between notochordal and chordoma cells morphologically and immunohistochemically (positivity for S-100 protein, cytokeratin [CK], and epithelial membrane antigen [EMA]). [4, 5, 6]
Chordomas have been divided into the following three subtypes:
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Conventional
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Chondroid
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Dedifferentiated
Chordomas present clinically as destructive bony masses with soft-tissue involvement. They erode and impinge upon adjacent structures, giving rise to a wide variety of clinical symptoms.
Treatment options include the following:
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Low-dose or high-voltage radiation therapy
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Combined radiation and surgery
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Surgical excision alone
It has been generally accepted that complete surgical excision of the tumor is the only curative procedure.
Pathophysiology
The notochord is derived from the primitive ectoderm and defines the midline of the chordate embryos. As the human fetus grows, the notochord expands at the site of the future intervertebral disks and forms the nucleus pulposus. The notochord regresses to leave an acellular sheath, except at its cephalic and caudal ends, where cell rests persist. Although this explains the observed distribution of chordomas (sphenoccipital and sacrococcygeal), it does not explain why the cell rests should transform into tumors.
Epidemiology
Chordomas can affect individuals of any age, including young children, but are most often diagnosed in individuals between the ages of 40 and 75 years (average age at diagnosis, 55 y). Chordoma is diagnosed in just one person per million per year. Thus, about 300 patients are diagnosed with chordoma each year in the United States and about 700 in all of Europe. At any given time, fewer than one in 100,000 people are living with chordoma. [7, 8]
Chordomas affect males more often than females, by a ratio of approximately 2:1; however, skull-base tumors have an equal (1:1) sex distribution. Children are more likely to have skull-base tumors, whereas spinal chordomas are more common in older individuals. Chordomas account for approximately 1-4% of all malignant bone tumors and 20% of primary tumors of the spinal column. Some reports have stated that these tumors are more common in individuals of European ancestry. [7, 8]
Prognosis
The 5-year and 10-year survival rates for conventional chordoma are approximately 50% and 25-30%, respectively. Conversely, chondroid chordoma has 5-year and 10-year survival rates of approximately 80%. Survival rates appear to be influenced more by local tumor progression than by metastasis. [9, 10] A higher survival rate is associated with Hispanic ethnicity, smaller tumor size, and surgical intervention.
All three types of chordomas can metastasize, usually later in the course of the disease (except dedifferentiated chordomas, which can metastasize early). The usual metastatic sites are skin, bone, lung, and lymph nodes. Accurate prediction of metastatic potential is not possible, though certain clinical (local aggressiveness) and pathologic (anaplastic histology) features may be indicative. Vertebral body chordomas have a higher incidence of metastasis than do those arising in the clivus or sacrum. [11]
Some data suggest that female sex, tumor necrosis, and tumor volume of more than 70 mL are independent poor prognostic variables in skull-base chordomas. The difference in survival rate between the sexes suggests that hormone receptor status and hormone manipulation management may be areas for future investigation. [12]
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MRI scan demonstrates an osteolytic lesion involving the vertebral body. This lesion occurred in the mobile vertebral column.
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Histologic section demonstrating lobular arrangement of tumor cells surrounded by fibrous connective tissue septa. Cellularity is variable with cells present in a pale myxoid matrix.
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S-100 immunostain of physaliphorous cells demonstrating strong nuclear staining.
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Cytologic preparation demonstrating characteristic physaliphorous cells with bubbly cytoplasm at higher magnification.
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Cytologic preparation demonstrating a sheet of low-grade polygonal large cells in a background of pale myxoid matrix.
