Pleomorphic xanthastrocytoma

Large expansile mixed solid and cystic mass centred on the right thalamus and an bulging superiorly to obliterate the right body of lateral ventricle. The right internal capsule and cerebral peduncle are displaced around the periphery of the lesion. Abnormal white matter FLAIR hyperintensity superior and lateral to the mass in the right external capsule temporoparietal region is compatible with vasogenic oedema.

The cystic component located superiorly has a complicated multiloculated appearance with innumerable small cystic spaces and septi demonstrating susceptibility artefact suggestive of haemosiderin staining. A few of these appear to layer on the SWI sequences suggesting fluid/fluid levels within some of the small cystic compartments. Enhancing rind surrounding the cystic component is thin superiorly but is thick and irregular inferiorly.

The solid component consists of a markedly expanded thalamus, largely non-enhancing apart from a 6 mm nodular enhancing focus anteriorly in the lesion. There is a mild cerebral blood volume (CBV) increase corresponding to the enhancing components, which demonstrate a tumoural trace (not shown) consisting of elevated choline, reduced NAA and a lactate peak.

There is a significant mass effect, with effacement of the third ventricle, distortion of the lateral ventricles and a 6mm midline shift to the left as measured at the septum pellucidum. The temporal horn of the right lateral ventricle is entrapped and dilated, while less pronounced enlargement of the left lateral ventricle is likely due to compression at the level of the aqueduct.

Conclusion:

Large right thalamic mass with solid and multicystic components causes gross mass effect on the midline, entrapment of the right temporal horn and moderate hydrocephalus due to aqueductal compression. Spectroscopy findings and elevated CBV suggest a high grade-grade tumour. However, given the relative paucity of symptoms for the degree of mass effect, the patient's young age and the lesion's relatively circumscribed margins a pilocytic astrocytoma or other low grade tumour-grade tumours (e.g. PXA) should be considered.