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General Information and Demographics
Chordomas are rare neoplasms comprising approximately 2% of all central nervous system tumors [1]. They are low grade mesenchymal tumors, most likely arising from notochord remnants. They are most commonly seen in the sacrococcygeal spine (50% of cases), though they may occur in the sphenooccipital area (35% of cases), as well as the cervical and thoracolumbar regions of the spine [2].
While a sacrococcygeal chordoma may develop at any age, it does so more frequently in the fifth and sixth decades [3]. The tumor grows slowly, and may be present many years before a clinical diagnosis is made. The presence of symptoms depends on the compression of surrounding structures by the tumor, such as those of spinal cord compression [4].
Cytologic Appearance
The cells in a chordoma are arranged in cell cords and lobules. A subset of these cells, known as 'physaliferous cells,' are typically large with vacuolated ('bubbly') cytoplasm and a prominent vesicular nucleus [5].
The nests are usually separated by a variable amount of matrix material, which appears fibrillary or myxoid, and looks metachromatic on Diff-Quik stained smears. Tumor cells in other regions may be smaller with inconspicuous nuclei. Mitotic figures are usually minimal to absent [5].
Immunohistochemical Profile
On cytologic preparations, chordomas can resemble other benign or malignant neoplasms; immunohistochemical stains are recommended to rule out other etiologies, before rendering a final diagnosis of chordoma.
On review of Romanowsky-type-stained aspirate smears, chordomas may be histologically similar to chondrosarcomas, myxopapillary ependymomas, and chordoid meningiomas [6]. In addition, some cases may resemble a mucinous adenocarcinoma. In the sacrococcygeal region, the presence of colorectal tumor extension must also be considered in the differential. For these reasons, formulation of an appropriate immunohistochemical panel is important.
Chordomas are typically immunoreactive for S100, keratins, and epithelial membrane antigen (EMA). Focal staining for carcinoembryonic antigen (CEA) has been reported [3].
Chordomas are not typically immunoreactive for CK7, CK20, GFAP, D2-40, MelanA, HMB45, Desmin, CD34 or smooth muscle actin. Staining for Ki67 reveals a low proliferative index. Positivity for GFAP is seen in chordoid meningiomas [6, 10]. D2-40 is useful to exclude extraskeletal myxoid chondrosarcomas [6, 10].
Histological Follow-up
The mass was subsequently excised (image 11). Histologic sections showed similar morphology, including a myxoid stroma, large cells arranged in cell cords and lobules, 'physaliferous cells,' rare mitotic activity and no necrosis (images 112 and 13).
Treatment and Prognosis
For sacrococcygeal chordomas, surgical resection is the treatment of choice [7]. Conversely, chordomas of the skull are typically difficult to resect, thereby prompting adjuvant chemoradiation therapy. Chordomas can recur and may even locally invade or destroy surrounding bone [8].
Despite the low grade nature of this tumor, distant metastases may occur in up to 43% of cases, particularly late in the disease course [3,9]. Skin and bone are the most common areas of spread, though other sites such as the ovary have been reported [9].
References
Contributed by Milon Amin, MD and Sara Monaco, MD
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