Petrous apex chondrosarcoma
4 weeks of of progressive right facial numbness involving second and third divisions of trigeminal nerve. ? demyelination.
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There is a large extra-axial mass with mass effect on the temporal lobe and brainstem. It appears to be arising from the either the posterior aspect of the right cavernous sinus or the right posterior clinoid process and clivus. On the sagittal sequences it has a broad dural attachment. It measures 37 x 33 x 34 mm (LR x AP x SI) and protrudes superiorly and posteriorly. The lesion demonstrates variable signal intensity on T1 and T2 imaging and variable contrast enhancement. Extensive punctate loss of signal on T2 and extensive susceptibility on gradient echo imaging suggests blood products and/or calcium, with the former favoured due to high signal on phase imaging. There is no restricted diffusion. The mass appears separate from the internal carotid artery and the sella. The mass appears separate from Meckel's cave which is displaced laterally and the lower margin of the cisternal trigeminal nerve. The lateral margin of the lesion effaces the right medial temporal lobe. The posterior margin displaces the upper pons, midbrain and cerebral peduncle posteriorly and medially. There is however no temporal lobe or brain stem oedema.
No other mass lesion. The remainder of the brain is normal. No evidence of demyelination.
Large right extra-axial mass probably centred on the posterior right cavernous sinus. The lesion is not typical for any single pathology and hence carries a differential diagnosis of atypical meningioma, atypical trigeminal schwannoma, haemangiomapericytoma or cavernous haemangioma. Alternative less likely diagnoses, as the lesion shows some features of a chondroid lesion, is a chondroma or chondrosarcoma of the clivus and right posterior clinoid process.
Further assessment with CT and CTA is advised to A) assess for osseous involvement and B) confirm the relationship with the ICA.
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The 30 x 40 mm mass located above the right petrous apex, involving Meckel's cave, is inseparable from the postero-lateral margin of the clivus, and has coarse central calcifications. There is local destruction of cortex.
Note that the right supraclinoid internal carotid artery has a close relationship to the mass, and that the right posterior cerebral artery is almost entirely fetal origin, the branch displaced by and covered by the mass.
Extracranial vessels are normal. No significant stenosis. No intracranial aneurysm or vascular malformation.
The additional information from the CT study effectively excludes neurofibroma or meningioma. Either chondrosarcoma or chordoma are the most likely diagnoses-the T2 signal characteristics more in favour of a chondrosarcoma. Note the close relation to the fetal right posterior cerebral artery which is displaced and on the medial border of the tumour, between right cerebral peduncle and postero-medial tumour margin.
MICROSCOPIC DESCRIPTION: Sections show a hypocellular cartilaginous tumour composed of sheets and lobules of chondroid matrix containing small chondrocytes. Occasional binucleate forms are present. Foci of necrotic cartilage are present. No cellular atypia or mitoses are seen. Cartilage is closely associated with mature bony trabeculae, however no permeation or destructive bone invasion is seen.
Multiple fragments of bone partly replaced by a chondroid proliferation with hilar matrix and paucicellular and bland appearing chondrocytes. However in areas the chondroid proliferation extends between pre-existing bony trabeculae and the occasional large irregular nucleus is noted.
FINAL DIAGNOSIS: Low grade chondroid tumour with features of low grade chondrosarcoma.