Primary Chordoma in the Nasal Cavity and Nasopharynx: CT and MR Imaging Findings

Discussion

Intracranial chordomas most often originate from the spheno-occipital synchondrosis of the clivus¹¹ and primarily present as a soft tissue mass with bone destruction in the skull base. Rarely, chordomas may arise from the nasopharynx,² maxilla,¹² and paranasal sinuses. When this happens, it is difficult to differentiate a chordoma from other tumors in the nasal cavity and nasopharynx. In the view of imaging features, tumors arising from the clivus, with extension into the nasopharynx and nasal cavity, are not included in the list of primary chordomas.

Chordomas may occur at any age but are usually seen in adults, with peak prevalence in the fourth decade of life. Intracranial chordomas have a 2:1 male predilection.^13,14 Our group consisted of 4 males and 1 woman (age range, 6–66 years). It is usually difficult to make a diagnosis of primary chordomas in the nasal cavity and nasopharynx through endoscopic examination and on clinical findings. In our group (except for 1 case), the tumors originated in the left nasal cavity; 4 tumors appeared as nasopharyngeal soft tissue masses and bulged into the posterior nasal choanal region; and, in 2 cases, there was fluid in the mastoid air cells secondary to obstruction of the ostium of the eustachian tube. Also, the tumors recurred in 4 cases. Weber et al¹⁵ reported distant metastases of intracranial chordomas to the lung, liver, bone, or lymph nodes with a proportion of 7% to 14%, whereas no metastases were observed in our study.

All lesions in our group formed a predominantly lobular soft tissue mass delineated by a fibrous pseudocapsule, which, because of adjacent tissue compression, accounted for the imaging appearance of being crisply marginated. Fluid and a gelatinous mucoid substance, associated with recent and old hemorrhages, and necrotic areas were found within the tumor. The variety of these components may explain the signal intensity heterogeneity observed on MR imaging.¹⁶ On microscopic examination, the notochord tissue is somewhat similar to immature cartilage and is composed of oval cells with central nuclei and a vacuolated cytoplasm embedded in an eosinophilic myxomatous stroma. The characteristic physaliphorous cells form the hallmark of chordomas.¹⁷

The 5 cases in our group revealed no bony involvement into the clivus, with only a large soft tissue mass in the nasal cavity and nasopharyngeal region. These localizations are best explained by the occurrence of extraosseous notochordal rests.¹⁸ Remnants of these notochordal branches that have penetrated these sites presumably provide the seed from which subsequent ectopic chordomas may grow.^19,20

The appearance of chordoma on CT images was that of a well-circumscribed, expansible soft tissue mass that arises from the nasal cavity, with linear calcification in 1 patient. In 4 patients, the lesions showed predominantly lobular morphologic features in the nasopharyngeal area with irregular focal calcification. Among them, 1 case showed minimal sequestra suggesting bony destruction. However, intratumor high intensity could be seen in 4 cases. The high attenuation of the tumor showed an irregular appearance (Fig 3). We postulate that the attenuation most probably represents intratumoral calcification rather than bone sequestra because there were no bony structures in the sites; this needs to be confirmed by immunohistologic studies. Solitary or multiple low-attenuation areas are sometimes seen within the soft tissue mass and probably represent the myxoid and gelatinous material seen on gross examination.^21,22

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Fig 3.

Case 3. Chordoma in the nasopharynx in a 13-year-old boy misdiagnosed with nasopharyngeal angiofibroma by nasal endoscopy. In the nasopharynx and left paranasopharyngeal space, the lobulated tumor exhibits irregular calcification (arrow) on CT images (A), isointensity on T1-weighted images (B), heterogeneous hyperintensity on T2-weighted images (C), and mild heterogeneous enhancement on postcontrast T1-weighted images (D), with clear margins with adjacent structures. The clivus has a normal signal intensity and appearance. The characteristic physaliphorous cells with large, sharply delimited, clear vacuoles imparting a bubbly appearance form the hallmark of chordoma (hematoxylin-eosin, original magnification × 400; E).

MR imaging provides excellent tissue contrast and exquisite anatomic details for radiologic evaluation of the nasal cavity and nasopharyngeal tumors. Compared with adjacent muscles, 5 cases revealed hypointensity or isointensity on T1-weighted images, and 4 lesions were heterogeneous. On T2-weighted images, 5 cases exhibited high heterogeneous signal intensity, a finding that likely reflects the high fluid content of vacuolated cellular components, as reported in the literature.²³ Intratumoral areas of calcification, hemorrhage, and a highly proteinaceous mucous pool usually demonstrate heterogeneous hypointensity on T2-weighted images (Fig 3). The fibrous septa that divide the gelatinous components of the tumor were clearly seen on the T2-weighted images as areas of low signal intensity. These septa have been reported in 70% of chordomas and are characteristic features of chordomas.²⁴ However, we only found these in 2 of 5 patients. Four cases of chordoma demonstrated mild to moderate enhancement after contrast material injection. The enhancement pattern of the tumor sometimes has a “honeycomb” appearance created by intratumoral areas of low signal intensity.²⁵ This pattern of contrast enhancement can reflect the pathologic features of such tumors, which are organized in lobules with mucinous and gelatinous contents.

However, MR imaging is deficient in the evaluation of calcification and cortical bone. Use of contrast-enhanced imaging can demonstrate osseous destruction if the tissue on the opposite side of the bone shows abnormal enhancement, which confirms bone involvement though the cortex is not actually visualized. Fat suppression may be useful for differentiation of enhanced tumor margins from adjacent fatty bone marrow. Combined CT and MR imaging is the desirable technique for the diagnosis and pretreatment evaluation.

Because of the definite location of the nasal cavity and nasopharynx, the differential diagnosis of chordoma should be made from other nasopharyngeal and nasal soft tissue masses. In the nasopharynx, 2 cases in the group were preoperatively misdiagnosed as nasopharyngeal carcinoma and juvenile nasopharyngeal angiofibroma. Usually, peak ages for the incidence of juvenile nasopharyngeal angiofibroma are within the second decade of life; these angiofibromas primarily arise from the region of the sphenopalatine foramen. Void of flow and considerable enhancement after injection of contrast material on MR imaging may support the diagnosis of the juvenile nasopharyngeal angiofibromas. A short history, predilection among the Asian population, bony destruction, and a soft tissue mass with limited calcification are the characteristics of nasopharyngeal carcinoma, and the nasopharyngeal mucosa is usually involved, as shown on postcontrast MR imaging. In the nasal cavity, the differential diagnosis between chordomas and chondrosarcoma is surely difficult on imaging and clinical examination. Some imaging features may be suggestive of chordoma including no destruction of the clivus, an expansible and lobular soft tissue mass with well-defined margins, and intratumor calcification.