Chondrosarcoma of skull base: grade II
64 year-old male presenting with progressive numbness in the first division of the trigeminal nerve (CNV1) and abducens cranial nerve (CNV6) palsy.
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Refer to MRI report below for combined CT and MRI image findings.
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A well defined lobulated mass measuring 3.5 x 3.5 x 5.8cm cm centered at the right clivus, crossing the midline by 4mm, is heterogeneous, but predominantly T1 hypointense, brightly T2 hyperintense, with loculated/bubbly internal enhancement. It has a well-defined thin sclerotic margin medially, and an ill-defined permeative margin laterally with mass effect upon the right anterior mesiotemporal lobe. There is breech of bony cortex posteriorly with a 14 x 6mm soft tissue projection that protrudes into the prepontine cistern, beneath dura, but lying in close proximity to the basilar artery. There is also destruction of the right carotid canal with small foci of ossific debris/coarse calcification that are T1 hyperintense. The right cavernous carotid artery is displaced, but its course lies predominantly inferomedial. Normal cavernous carotid flow void is preserved although mild narrowing is present. The right cavernous sinus and Meckel's cave are obliterated. The lateral wall of the right sphenoid sinus is remodelled, and intact, with the sinus well aerated. Part of the superolateral wall of the right foramen rotundum is breached. Right foramen ovale is slightly widened. The right hypoglossal canal is breached superiorly. Tumor lies close to the right optic canal, but the optic canal is not compromised. Inferiorly, a tongue of tissue has protruded into the right longus capitis muscles, but is 7mm from the right nasopharyngeal mucosa.Right cochlear and vestibular apparatuses, middle ear and mastoid uninvolved. Right jugular foramen also appears uninvolved. Minor chronic small vessel ischemic change. No diffusion restriction. Thickened left maxillary sinus walls with mild mucosal thickening in keeping with chronic sinusitis.
Conclusion: Right central skull base tumor most likely to represent chondrosarcoma or (eccentric) chordoma with extent as described.
The patient underwent a right pterional craniotomy and resection of the skull base tumor.
Paraffin sections show a tumour of varying hypercellularity composed largely of circumscribed lobules of chondroid material in which tumour cells are haphazardly arranged in lacunae. Many lacunae contain multiple tumour cells. Tumour cells show mild nuclear atypia. An occasional mitotic figure is identified. Other areas of tumour are composed of single and small aggregates of tumour cells dispersed in a mucinous/myxoid stromal matrix. No areas of necrosis are identified. Lobules of chondroid tumour tissue are seen to permeate between trabeculae of native bone. Moderate bone remmodelling is seen. The overall features are of chondrosarcoma - grade II.
DIAGNOSIS: Skull base tumour: Chondrosarcoma - Grade II
The patient had an uneventful post-operative recovery and has remained stable and under annual radiological surveillance.
This case illustrates the typical radiological appearances of a type of skull base tumor known as a chondrosarcoma. Chondrosarcomas constitute approximately 11% of all malignant bone tumors1. Chondrosarcomas of the skull base are rare and slow-growing lesions, accounting for account for 6% of skull base neoplasms and 0.15% of all intracranial tumors 2,3. The cytological origin of skeletal chondrosarcoma is unknown, and is thought to arise from a combination of cartilage, endochondral bone, or primitive mesenchymal cells in the brain or meninges4, 5. The most common locations for these malignant extra-axial tumors are the petrous portion of the temporal bone and areas of the petro-occipital, spheno-occipital, and sphenopetrosal synchondroses2, 4. Histologically, three subtypes are differentiated: classic, myxoid and mesenchymal, with subdivision into three grades (as per the World Health Organization classification system): categories: grade I (well differentiated), grade II (moderately differentiated) and grade III (poorly differentiated)1, 3.
On neuroimaging with CT, these tumors are well-delineated and extra-axial, with a isodense to hyperdense appearance and heterogeneous contrast enhancement3, 6. On MR imaging, chondrosarcomas appear hyperintense on T2-weighted imaging, hypointense on T1-weighted images, and with intense heterogeneous post-contrast enhancement1, 6. Despite the typical neuroimaging findings of chondrosarcomas, meningiomas and metastases have to be differentiated/excluded1.
Case courtesy of Dr. Frank Gaillard
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