This case demonstrates features characteristic of CNS lymphoma (primary in this case), and highlights the importance of understanding the general histological makeup of lesions if imaging is to be adequately interpreted. The densely cellular and 'small round blue cell' appearance manifests as hypderdensity on CT and restricted diffusion on MRI, with out the heterogeneity or non-enhancing components of glioblastomas. 

Although this is not an intra-ventricular lesion, the striking periventricular distribution and exophytic thalamic component means that it is useful to think of this lesion in the context of intraventricular pathology, which can often (e.g. ependymoma) have a parenchymal component.