Skull base chondrosarcoma
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A very large mass, which has destroyed the left inferolateral aspect of the clivus, extends laterally through the floor of the left middle cranial fossa as far as its lateral wall. It extends inferiorly through the destroyed floor into the infra temporal fossa and posteriorly impinges upon the pons immediately to the left of midline. It contacts the left side of the basilar artery, but does not appear to encase it. The left internal carotid artery is markedly displaced laterally, almost to the lateral wall of the left middle cranial fossa. It is totally encased by the tumour as it emerges from carotid canal, but remains patent. Posterolaterally it has invaded through the destroyed petrous bone to abut the left cerebellar hemisphere. It occupies the jugular bulb and abuts the left internal auditory meatus on three sides.
Conclusion : Very large extension of left sided "clival chordoma" to almost entirely occupy the anterior aspect of the left middle cranial fossa, a small portion of the posterior fossa and the upper portion of the left infratemporal fossa.
Pathology report on repeat surgery.
The sections show a moderately cellular tumour with a lobulated architecture. There are aggregates of epithelioid cells in blue-tinged chondroid-like stroma. The tumour cells have mildly enlarged and hyperchromatic nuclei, angulated nuclear contour, small nucleoli and small to moderate amounts of clear vacuolated to eosinophilic cytoplasm. No mitoses or necrosis is seen. Sections of the bone show tumour infiltrating into the medullary spaces. The tumour cells are S-100 positive. There is focal staining for M2A. EMA staining is equivocal. CAM5.2, AE1/3, CK19 and CEA are negative.
Comment: The previous biopsy has been reviewed. It showed similar morphology as compared to the current tumour with cellular nodules of cartilage, containing atypical chondrocytes. CAM5.2 was also negative. The overall features are those of grade 2 chondrosarcoma. Cytokeratin negativity excludes the diagnosis of chordoma .
The radiology has also been reviewed and chondrosarcoma is favoured over chordoma.
Final diagnosis : Skull base tumour: Recurrent grade II chondrosarcoma.