Figure 2. . Imaging findings.

Axial postgadolinium T1-weighted images on MRI revealed a heterogeneously enhancing mass lesion in the diencephalon (white arrow), anterior and right of the third ventricle (A). The mass continually decreased in size by 2 months (B) and 5 months (C) after initiation of combination BRAF and MEK inhibitors. 18-Fluoro-deoxyglucose PET (FDG-PET) images revealed FDG-uptake in a circular mass lesion (black arrow) greatly reduced in size after treatment (G & H) compared with baseline (E & F). Cortical metabolic activity in the right hemisphere (*) was markedly decreased compared with the normal contralateral cortex (**) in the pretreatment FDG-PET (E), while the bihemispheric FDG uptake normalized post-treatment (H). FLAIR MRI reveal near disappearance of the tumor and edema at 7 months after treatment (I) compared with pretreatment (D).

FDG-PET: 18-Fluoro-deoxyglucose PET; FLAIR: Fluid-attenuated inversion recovery.