Presentation
Personality change.
Patient Data
A large right frontal lobe hypodense mass with subfalcine herniation is present. No definite enhancement or necrosis.
A very large tumor occupies the majority of the right frontal lobe extending across and thickening the corpus callosum into the left frontal lobe. It is primarily low T1 high T2 in signal without nodular enhancement; at most there are wispy areas of enhancement at the margins. No obvious necrosis. Large portions of the tumor demonstrate T2/FLAIR mismatch. Minor areas of blood product are seen in the medial component, that herniates below the falx. These are not calcifications. High T2 signal also extends down the right insula and into the temporal pole. CBV is low. MRS demonstrates a high Choline peak. Diffusion is facilitated
Ventricles are compressed with some obstruction to their outflow at the foramen on Munro.
Conclusion:
A large frontal tumor is almost certainly an adult-type diffuse glioma, most likely an astrocytoma. Although there are no definite high-grade features on imaging, in this age group the majority of tumors (~80% 1) will be IDH-wildtype and thus a molecular glioblastoma is the most likely diagnosis.
Case Discussion
The patient went on to have a partial resection.
Histology
Sections show brain widely infiltrated by a diffuse glioma. The tumor cells have enlarged oval-to-angulated nuclei, with fairly coarse chromatin. They are set within a fibrillar background that also contains plentiful mucin. Mitoses are easily identified. There is no necrosis but focal microvascular proliferation is identified.
Immunohistochemistry:
- IDH-1 R132H: positive (mutant)
- GFAP: positive
- OLIG2: positive
- ATRX: negative (mutant)
- p53: positive (mutant)
- p16 CDKN2A: positive (not lost)
- Ki67: 10%
FINAL DIGANOSIS: adult-type astrocytoma, IDH-mutant (CNS WHO grade 4)
Discussion
This case nicely illustrates how even in older individuals IDH-mutant astrocytomas are sometimes encountered, however, their prevalence is highly determined by age.