Gemistocytic astrocytoma (anaplastic)
Headache and seizure.
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Large intra-axial ill-marginated right frontal lesion. Heterogeneous enhancement over 3.5 x 4.5cm (axial), corresponding to areas of diffusion restriction and patchy increased CBV. Elevation of choline, NAA depression, myo-inositol elevation and a lactate peak are noted on MRS. There are patchy internal areas of non-enhancement. Extensive surrounding bright flair signal involving the white matter and cortex. Medially this bright signal extends to the subependymal region of the anterior right lateral ventricle and internal capsule anterior limb. Superiorly it extends into the centrum semiovale at level of middle frontal gyrus. Inferiorly it extends through the right insular into the anterior right temporal lobe.
There is significant mass effect, with right uncal herniation and midbrain distortion, and 1.1 CM leftward midline shift of the septum pellucidum. There is effacement of the right lateral ventricle, and entrapment of the left lateral ventricle with periventricular bright flair signal is seen.
Mildly prominent left retrocerebellar extraaxial CSF space is noted, probably incidental.
Conclusion: The mass is clearly a primary brain tumour, with grade III or IV components. The size and heterogeneity of the lesion with cystic and ill defined FLAIR suppressing areas (separate to the enhancing component) suggesting an underlying non-fibrillary subtype (esp gemistocytic).
The patient went on to have debulking.
MICROSCOPIC DESCRIPTION: All the sections show a densely cellular astrocytic tumour. The astrocytes form sheets. Most of these cells are gemistocytes with enlarged hyperchromatic nuclei and moderate amounts of eosinophilic cytoplasm. Scattered mitoses are seen. There are occasional foci of mild endothelial cell hyperplasia. Necrosis is absent. Perivascular lymphocytes are seen. There is tumour involving the cerebral cortex. The features are those of anaplastic astrocytoma of the gemistocytic type (gemistocytic astrocytoma). IDH-1 immunostain is positive. The Ki-67 index is about 8%.
DIAGNOSIS: Anaplastic gemistocytic astrocytoma (WHO grade III).
This is a fairly typical appearance for a gemistocytic astrocytoma, with little difference in appearance between WHO Grade II and Grade III lesions on imaging. Both tend to be large tumours, most commonly located in the frontal lobes, with areas of non-enhancement, partial suppression on FLAIR, cystic change and enhancement.
The differential is really only of a WHO grade IV lesions, GBM.