Primary CNS lymphoma

A large enhancing, mildly irregular mass is centered on the genu of the corpus callosum in the frontal lobes, crossing the midline involving both the left and right frontal lobes with extensive surrounding vasogenic edema. A further similar mass is seen just inferiorly within the inferior left frontal lobe. There is significant mass-effect with compression of the frontal horns of both lateral ventricles and approximately 5 mm of midline shift to the right at the level of the body of the lateral ventricles. No hydrocephalus. No hemorrhage.

A third and different lesion appearing partly calcified and enhancing is extra axial deep to the inner table of the right pterion is suggestive of a meningioma. 

Conclusion: Enhancing frontal mass lesions centered on the genu of the corpus callosum most likely represents a lymphoma or high-grade butterfly glioma. Given the clinical history, metastatic disease is also a possibility but felt less likely. 

The genu of the corpus callosum is expanded by a centrally low T1/high T2 signal mass which demonstrates avid homogeneous enhancement and extends into both frontal lobes. Prominent restricted diffusion and elevated CBV.  No midline shift or hydrocephalus.

At the inferomedial aspect of this lesion, there is a small region of low T2 signal with blooming on EPI, some intrinsic T1 high signal and enhancement that has a leptomeningeal component. This is consistent with a focus of hemorrhage. There is extensive FLAIR hyperintensity within both frontal lobes surrounding the lesions, which predominantly involves white-matter. The high FLAIR signal extends into the left internal capsule.

Multiple small foci of further enhancement are seen including in the left superior frontal gyrus and left medial cerebellar hemisphere

Incidental pteryonal meningioma.

Conclusion: Features most likely represent primary CNS lymphoma.