Extraventricular neurocytoma and ganglioneurocytoma: advanced MR imaging, histopathological, and chromosomal findings.

Extraventricular neurocytoma and ganglioneurocytoma are rare intra-axial brain neoplasms that are now recognized as distinct entities in the 2007 WHO classification of brain tumors. We describe the conventional MR imaging, perfusion MRI, proton MR spectroscopy (1H MRS), histopathology, immunohistochemistry, and chromosomal analysis in two cases of these tumors, with some features which have not been previously well described. Both tumor types demonstrated markedly elevated cerebral blood volume on perfusion MRI and had 1p19q chromosomal codeletions. Both tumor types showed an elevated Cho/Cr ratio, but extraventricular ganglioneurocytoma showed a preserved NAA/Cr ratio. These tumors should be considered in the differential diagnosis of intra-axial brain tumors.