PET Imaging of a Butterfly Glioblastoma

In magnetic resonance imaging (MRI) a robust contrast enhancement usually includes glioblastoma. However, in a small percentage (4%) of patients with glioblastoma (GBM), there is minimal or even lacking contrast enhancement on MRI. We report the neumimaging findings in a 37-year-old woman with a "butterfly" GBM. In contrast to a clearly bilateral increased (11)C-11 methionine (MET) positron emission tomography (MET-PET) uptake pattern, contrast enhancement on MRI was only slightly increased despite a large tumor extension. The extent of the metabolically active tumor mass delineated by MET-PET was larger than the MRI lesion. Whereas MRI suggested a bifocal growth, MET-PET showed a widespread but continuous tumor mass. In this case of bihemispheric GBM, MRI findings were ill-defined and ambiguous. MET-PET imaging added substantial diagnostic information that strongly suggested the diagnosis of GBM and helped to delineate the tumor extension.