Astrocytoma, IDH-mutant - grade 3 - gliomatosis growth pattern

Much of the left hemisphere is of abnormal T2 signal with multiple areas demonstrating gyral expansion. Deep to the expanded cortex of the left middle frontal gyrus are areas of faint enhancement. No overt necrosis or hemorrhage. Abnormal signal also spreads across the corpus callosum into the right hemisphere. Significant mass effect with midline shift.

Conclusion:

The appearances are those of an adult-type diffuse glioma with extensive involvement and a gliomatosis growth pattern. The presence of areas of enhancement suggests a higher grade (e.g. WHO grade 3).

Both specimens have similar features and consist of fragments of a moderately cellular glial tumor. Tumor cells diffusely infiltrate within a fibrillary background. Many of the tumor cells have gemistocytic morphology. Tumor nuclei are ovoid, hyperchromatic and moderately pleomorphic. Two mitoses are seen within one fragment. Necrosis and microvascular proliferation are not identified.  

Immunohistochemistry:

• Ki67: 5%

• p16 CDKN2A: positive (not lost)

• p53: positive (mutated)

• ATRX: lost (mutated)

• IDH-1 R132H: positive (mutated)

• OLIG2: Positive

• GFAP: Positive

Final diagnosis:

Astrocytoma, IDH-1 R132H-mutant, WHO grade 3