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 tumors ¹. 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 meninges ^4,5. 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 synchondroses ^2,4. Histologically, three subtypes are differentiated: classic, myxoid and mesenchymal, with subdivision into three grades (as per the World Health Organization classification system): 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 enhancement ^3,6. On MR imaging, chondrosarcomas appear hyperintense on T2W imaging, hypointense on T1W images, and with intense heterogeneous post-contrast enhancement ^1,6. Despite the typical neuroimaging findings of chondrosarcomas, meningiomas and metastases have to be differentiated/excluded ¹.

Case courtesy of Dr. Frank Gaillard