Chondrosarcoma of the petroclival synchondrosis

The patient is a 57-year-old, right-handed, retired postal worker. He presented with a chief complaint of left-sided facial tingling. The episodes of paresthesia last only a few seconds, but have persisted for 7 years.

There have also been episodes of dizziness and imbalance. He denied headaches. His only significant past medical history includes hypertension and anxiety disorder.

On physical examination, no cranial nerve deficit was evident. Specifically, sensory and motor function of the trigeminal nerve and extraocular muscle function were intact.

Scanning results

MRI of the brain demonstrated a T2 hyperintense, heterogeneously enhancing, destructive mass centered at the left petroclival synchondrosis. There was anterior displacement of the petrous segment of the internal carotid artery, as well as partial effacement of the left Meckel’s cave. There was a small component of posterior extension into the left prepontine cistern. The superior portion of the tumor extended into the left middle cranial fossa, without parenchymal edema in the adjacent temporal lobe. The superior portion of the tumor had stronger enhancement than the inferior portion.

A preoperative postcontrast, high-resolution CT examination exhibited osseous destruction centered at the foramen lacerum, involving the lateral clivus and medial petrous apex. The superior component of the tumor contained punctate and arc-like areas of calcification (in contrast to the irregular remnants of the destroyed portion of the petrous apex). The superior component of the tumor also had slightly higher attenuation than the inferior component of the tumor, which may reflect higher density, enhancement or a combination.

Axial postcontrast CT images. Panel A shows relatively higher attenuation of the tumor in its craniad component, adjacent to the medial temporal lobe. There are curvilinear hyperdensities (arrow) consistent with chondroid matrix. Panel B shows a more hypodense inferior portion of the tumor (arrowhead), anterior to the partially destroyed petrous apex. Photos courtesy of M. Ghesani, MD

Axial postcontrast T1-weighted images with fat saturation. Panel A shows relatively brisk enhancement of the superior portion of the tumor (arrow), corresponding to the area of calcifications seen in Figure 1A. Note anteromedial displacement of the flow void for the left internal carotid artery (short arrow in panel A). Panel B shows a lesser degree of enhancement at the inferior portion of the tumor (arrowhead), corresponding to Figure 1B, with mild extension into the prepontine cistern.

Coronal reformatted image from the CT examination shown in Figure 1, bone algorithm (panel A). The curvilinear calcifications in the superior portion of the tumor (arrow) are consistent with a tumor of chondroid origin. Coronal T2 weighted image (panel B) shows signal hyperintensity of the tumor.

Chondrosarcoma. Most areas of the tumor consist of a cellular proliferation of small rounded chondrocytes distributed in a copious myxoid matrix (panel A, H&E, 100x). These cells are focally arranged in cords and trabeculae, have pale eosinophilic to clear cytoplasm, and slightly enlarged nuclei with occasional binucleation. Some areas of the tumor show more obvious cartilaginous differentiation with lobules of well-formed hyaline cartilage (arrows in panel B, H&E, 100x) and entrapped trabecular bone (left lower quadrant of panel B).

The patient underwent surgical resection of the tumor. Histologic findings were consistent with a chondrosarcoma (CSA), predominantly myxoid type. Distinguishing the tumor from chordoma, the main differential diagnostic consideration, was difficult and required the use of multiple immunohistologic stains.

Discussion

Although CSA may account for up to one-third of primary bone malignancies, the intracranial variety is much rarer, making up less than 1% of all intracranial tumors. Origin from rests of fetal cartilage, which are remnants of intramembranous ossification of endochondral bone, gives CSA a predilection for the petroclival, sphenopetrosal, petro-occipital and spheno-occipital synchondroses of the skull base. CSA may also arise from malignant degeneration of enchondroma, as in Ollier’s disease and Maffucci’s syndrome.

The clinical presentation of CSA will largely depend on the specific anatomic areas involved. Headache is common. More specific symptoms that point to involvement of particular cranial nerves are common, especially diplopia due to involvement of the abducens nerve as it crosses the petrous apex, or facial pain due to the tumor’s proximity to Meckel’s cave and the cavernous sinus, involving the trigeminal nerve.

Virtually all skull base CSA are of the conventional type, which may be composed of myxoid matrix, hyaline matrix or, most often, a combination of the two. The hyaline type has a more solid tumor matrix than the myxoid type and may feature calcifications that characteristically take a curvilinear shape on imaging, often described as “rings and arcs.” Matrix calcifications may be seen in about one-half of cases of skull base CSA.

As in this case, lobulated morphology with T2 hyperintensity on MRI is characteristic. Bone destruction is evident on CT in most cases. In this case, the tumoral component with stronger CT hyperdensity and gadolinium enhancement, as well as calcifications, likely represents an area of hyaline matrix, whereas the component with relative CT hypodensity and less brisk contrast enhancement is likely composed predominantly of myxoid matrix.

Daniel E. Meltzer, MD, is an assistant professor of radiology at St Luke’s-Roosevelt Hospital Center.

Ali Noor, MD, is a resident, PG-4, diagnostic radiology at St Luke’s-Roosevelt Hospital Center.

Yinghua Pang, MD, is a resident, PGY-3, anatomical and clinical pathology at St Luke’s-Roosevelt Hospital Center.

Arzu Buyuk, MD, is an assistant professor of pathology at St Luke’s-Roosevelt Hospital Center and Roosevelt Hospital Surgical Pathology.

Munir Ghesani, MD, is an attending radiologist at St. Luke’s-Roosevelt Hospital Center and associate clinical professor of radiology at Columbia University College of Physicians and Surgeons.

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Disclosures: The authors report no relevant financial disclosures.