Diagnosis

Bilateral fronto-parietal peri-ventricular and subependymal mass lesion with infiltration of the forceps major and corpus callosum as described; the conventional and MR spectroscopic criteria is in favor of primary CNS lymphoma. The differential is high grade glioma (GBM), however the lack of significant perifocal edema, mass effect and lack of  typical pattern of thick irregular rind of enhancement, as well as the multifocal subependymeal and periventricular nature of the lesion, strongly suggests primary CNS lymphoma, rather than high grade glioma.