Chordoma - Chordoma

Chordoma
last edited by Matt Steensma on Oct 01, 2008
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Epidemiology

Chordomas are thought to arise from primitive notochordal remnants in the axial skeleton. For this reason, chordomas universally present in a central, axial-based location, most often anteriorly. The cumulative case count published in The Burden of Musculoskeletal Disease (AAOS) identified 2,339 chordomas over a period of twenty years. This amounts to an annual incidence of 117 chordomas in the United States within the studied population. Other estimates are as high as 300 per year. The most common location is the sacrum (52%), followed by the base of the skull (35%). The remaining lesions can occur anywhere in the cervical, thoracic or lumbar spine (13%). The average age of diagnosis of sacral chordomas is 55, however the age range is broad. Cranial-based tumors occur in slightly younger patients. Males are affected more frequently than females. The median survival is 6 years. Overall survival rates are 70% at 5 years, 40% at 10 years. After the development of metastases, median survival diminishes greatly.

Pathology

The histologic appearance of chordoma is distinct. Tumor cells are separated into lobular regions separated by fibrous septae. The high mucin content within cytoplasm and in the matrix renders a deep, eosinophilic appearance on H&E stained sections. The physaliphorous cell is the sine qua non of chordoma and is characterized by prominent cytoplasmic vacuoles that displace the nucleus eccentrically. A chondroid appearance has been described particularly in clival-based tumors, and may portend a better prognosis. There is also a dedifferentiated form of chordoma that, similar to other dedifferentiated neoplasms, has a poor prognosis. Malignant fibrous histiocytoma, fibrosarcoma, osteosarcoma and rhabdomyosarcoma have been known to arise from chordomas, granted this is an uncommon occurrence. Chordomas are characterized immunohistochemically by S100 and epithelial membrane antigen positivity.

Presentation

Symptoms of chordoma are usually nonspecific and dependent on the location of the tumor. Lesions in the cervical spine can cause hoarseness, dysphagia, or bleeding. Sacral lesions can be accompanied by vague low back pain, constipation, lower extremity radiculopathy, or a palpable mass. Bowel and bladder dysfunction can be a direct result of local organ mass effect or autonomic dysfunction. Autonomic dysfunction can result as the tumor compresses the adjacent sympathetic or parasympathetic outflow. On average, diagnosis of chordoma is made 10 months after the onset of symptoms.

Imaging
The typical xray appearance of chordoma is a lytic, destructive lesion with a large soft tissue shadow. Often, these findings are masked by overlying abdominal contents on routine AP pelvis. CT scan is useful to assess the degree of osseous involvement, as well as proximity of the tumor mass to adjacent pelvic organs. MRI gives superior soft tissue resolution with respect to involvement of neurovascular structures within the pelvis as well as the spinal canal. Because of the mucinous content of chordomas, they typically appear hypointense on T1-weighted images and hyperintense on T2-weighted images. The lobular, heterogeneous features characteristic of this tumor are usually apparent. Occasionally, contrast fluid-fluid levels can be identified in cystic portions of the mass.
Treatment
Surgical resection is the mainstay of therapy as chemotherapy is ineffective. Isolated responses have been documented, however meaningful increases in survival have not been validated. Wide resection can be curative, however a 50% recurrence rate has been reported. Resection of upper sacral lesions (S2 or above) carry an increased risk of blood loss, major complications, and longer ICU stays.

Therapy targets are being studied in Chordoma. A recent investigation identified the presence of platelet-derived growth factor beta (PDGF-B) expression in clinical samples. This observation has led to the administration of imatinib in selected cases with subjective improvement in tumor size based on MRI and CT imaging. To date, no complete response has been documented, however investigations are ongoing.

Recommended Readings

Cancer. 2004 Nov 1;101(9):2086-97. Imatinib mesylate in chordoma.Casali PG, Messina A, Stacchiotti S, Tamborini E, Crippa F, Gronchi A, Orlandi R, Ripamonti C, Spreafico C, Bertieri R, Bertulli R, Colecchia M, Fumagalli E, Greco A, Grosso F, Olmi P, Pierotti MA, Pilotti S.

J Surg Oncol. 2006 Sep 1;94(3):203-11. Level-adjusted perioperative risk of sacral amputations.Devin C, Chong PY, Holt GE, Feurer I, Gonzalez A, Merchant N, Schwartz HS.

Orthopaedic Pathology. Bullough P. 4th ed. Mosby 2004.

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