Chordomas

Chordomas can be classified into three subgroups. The most common are the conventional chordomas, which are distinguished by the absence of mesenchymal elements such as cartilage. On histologic examination, lobules of epithelioid cells are arranged in cords, separated by a mucinous matrix. Tumor cells have vacuolated, bubbly cytoplasm, earning the name “physaliphorous cells.” Nuclear pleomorphism and mitoses are rare. Chondroid chordomas contain chondromatous and chondromatous features and often occur in the spheno-occipital region. Both the conventional chordomas and chondroid chordomas have similar prognoses. The third type includes chordomas that undergo sarcomatous transformation; these have a worse prognosis because they behave more aggressively. Histologically, the sarcomatous component is interspersed between areas of conventional chordoma. Although chordomas are slow growing, they tend to recur and occasionally metastasize.

Clinical Manifestations. Signs and symptoms depend on the location of the tumor and its effect on neighboring structures. Local pain is a common complaint. With skull base involvement, patients often complain of headache and diplopia secondary to invasion of the cavernous sinus. Involvement of the lower clivus may affect the lower cranial nerves, resulting in dysphagia or hoarseness, followed by brainstem compression. Because the onset of symptoms is quite insidious and vague, diagnosis is often delayed. Tumors of the spinal column and sacrum can cause back pain. Direct compression from spinal column tumors can lead to cord compression. Occasionally, the tumors of the sacrococcygeal region may reach enormous proportions, resulting in bladder and bowel dysfunction due to direct pressure on the rectum and involvement of sacral nerves.

Diagnostic Studies. Both MRI and CT are used for diagnostic purposes. MRI provides detailed anatomy, providing the ability to assess the extent of soft tissue and dural involvement. CT is more effective for delineating bony lesions. There is no pathognomonic imaging findings, thus histopathologic examination from a tissue specimen is required for a definite diagnosis.

Treatment. Because of the rarity of the tumor, there are no set guidelines for treatment of chordomas. Based on small retrospective studies, a multimodal approach, combining surgery with radiotherapy, is recommended. Surgery is used for both diagnostic and therapeutic purposes; it allows for a tissue diagnosis and reduces tumor burden. Complete resection is the goal but often not feasible due to the anatomic constraints of the tumor. Their invasive nature results in a high incidence of local recurrence, and about 2% to 8% of chordomas will undergo sarcomatous transformation. Salvage therapy may include repeat surgery or radiation treatment.

Adjuvant radiotherapy has been employed with increasing frequency, especially with current advances in radiation equipment and technique. Historically, conventional radiation with photons was difficult to administer because the required doses were often associated with increased risk of damage to important structures such as the brainstem or cranial nerves. With newer techniques using proton therapy, stereotactic radiosurgery, or intensity modulated radiation therapy (IMRT), outcomes have significantly improved by allowing higher doses of radiation while minimizing injury to neighboring structures.

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