Meningioma - posterior falx


Sometimes it can be difficult to distinguish intra and extra-axial tumors, especially when they are large nestled deep in a sulcus or the interhemispheric fissure. In this case it invaginates the splenium of the corpus callosum with significant edema. 

One could be tempted to consider a GBM or even lymphoma, although on careful inspection a cleft can be seen between the mass and the adjacent corpus callosum. It is clearly remote from the pineal gland, being located above the internal cerebral veins.