3-year-old male presenting with a well-circumscribed mass lesion in the left brachium pontis with solid and cystic components that is hyperintense on T2-weighted axial MRI (A) and hypointense on T1-weighted MRI (B). Postcontrast T1-weighted MRI (C) demonstrates heterogeneous enhancement in the solid portion of the mass. There is no diffusion restriction on diffusion-weighted (D) and apparent diffusion coefficient (E) images. Pathology at the time of resection was consistent with pilocytic astrocytoma, WHO grade 1, positive for KIAA1549:BRAF fusion.
MRI: magnetic resonance imaging; WHO: World Health Organization.
