Figure 9b. Exophytic pilocytic astrocytoma arising from the brainstem. (a) Axial CT image shows a hypoattenuated mass (m) of the posterior margin of the mid-pons and left cerebellar hemisphere. (b) Axial T2-weighted image reveals heterogeneous hyperintensity of the mass, which extends into the adjacent cisternal space (arrow). (c) Contrast-enhanced axial T1-weighted image demonstrates intense enhancement of the soft-tissue nodule (n) and lack of enhancement of the cystic portion. Extension into the cerebellopontine cistern is again noted.