Background Glioblastoma multiforme (GBM) typically presents in the supratentorial white matter, commonly within the centrum semiovale as a ring-enhancing lesion with areas of necrosis. An atypical presentation of this lesion, both anatomically as well as radiographically, is significant and must be part of the differential for a neoplasm in this anatomical location. Case Description We present a case of a 62-year-old woman with headaches, increasing somnolence, and cognitive decline for several weeks. Magnetic resonance imaging demonstrated mild left ventricular dilatation with a well-marginated, homogeneous, and nonhemorrhagic lesion located at the ceiling of the third ventricle within the junction of the septum pellucidum and fornix, without exhibiting the typical radiographic features of hemorrhage or necrosis. Final pathology reports confirmed the diagnosis of GBM. Conclusion This case report describes an unusual location for the most common primary brain neoplasm. Moreover, this case identifies the origin of a GBM related to the paracentral ventricular structures infiltrating the body of the fornix and leaves of the septum pellucidum. To our knowledge this report is the first reported case of a GBM found in this anatomical location with an entirely atypical radiographic presentation.
Keywords: foramen of Monroe; fornix; glioblastoma multiforme; gliosarcoma; hydrocephalus; septum pellucidum; third ventricle.