Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
Sign up to receive an email alert when a new Case of the Week is posted.
November 21, 2019
T2-FLAIR Mismatch in IDH-Mutated Glioma (Anaplastic Astrocytoma)
- Background:
- The 2016 World Health Organization Classification of Tumors of the Central Nervous System introduced the use of molecular markers in addition to histopathology to define several entities. Notably, diffuse gliomas that are IDH-mutated and 1p/19q noncodeleted are associated with better survival rates.
- Studies have shown that in grade II and III gliomas, increased signal intensity on T2 and attenuated signal on FLAIR sequences (T2-FLAIR mismatch) are predictive of IDH-mutated status with high specificity and positive predictive value.
- Clinical Presentation:
- Depends on location and size
- Most commonly, patients present with headaches (50%–60%) followed by seizures and focal neurologic symptoms (eg, weakness, visual changes, language deficits) and in some cases cognitive dysfunction and personality changes.
- Key Diagnostic Features:
- Diffuse gliomas tend to be hypointense on T1WI and hyperintense on T2WI.
- Anaplastic astrocytomas (grade III) primarily involve the white matter; enhancement is variable but usually absent.
- In grade II/III gliomas, increased signal on T2WI and decreased signal on FLAIR are highly predictive of IDH-mutant, 1p/19q noncodeleted status.
- Differential Diagnoses:
- Diffuse astrocytoma (grade II): May be indistinguishable on conventional imaging; rCBV is lower than that in grade III and IV tumors.
- Glioblastoma (grade IV): Heterogeneous enhancement with central necrosis, frequently accompanied by hemorrhage; solid components may show restricted diffusion due to high cellularity.
- Oligodendroglioma (grade II or III): May be indistinguishable from other diffuse gliomas, but preferential cortical/subcortical involvement with gyral expansion and calcifications are highly characteristic. Enhancement is variable and may show elevated rCBV. Higher rCBV, necrosis, and hemorrhage are suggestive of grade III (anaplastic) oligodendrogliomas.
- Abscess: Following the stages of early and later cerebritis, an abscess develops an enhancing capsule and shows central restricted diffusion.
- Necrotic metastasis: Presents with peripheral enhancement, may be hemorrhagic, and can occasionally be indistinguishable from a glioblastoma. Peritumoral rCBV values are typically lower than those in high-grade gliomas.
- Treatment:
- Typically consists of maximal safe resection followed by radiation and chemotherapy
