Gemistocytic astrocytoma IDH-mutant [Neurosurgery Wiki]

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====== Gemistocytic astrocytoma IDH-mutant ======

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[[Gemistocytic]] differentiation is a rare histological feature seen in IDH mutant Astrocytomas. The [[World Health Organization Classification of Tumors of the Central Nervous System 2021]] retains the diagnosis of 
[[Astrocytoma IDH-mutant]] with its classical histology and tumors with the rare histological pattern of [[gemistocytic]] differentiation.

A [[WHO grade II]] variant of [[diffuse astrocytoma IDH mutant]] distinguished by gemistocytes comprising > 20% of tumor cells. They make up ≈ 10% of WHO grade II diffuse astrocytomas. Mean age at diagnosis is 40 years.

===== Histology =====
Gemistocytes appear as astrocytes with glassy, plump, angular eosinophilic cell bodies, and contain GFAP-positive cell processes.

===== Molecular biology =====
[[TP53 mutation]]s appear to be highly represented (> 80%) in all gemistocytic astrocytomas, and this is likely to be higher among IDH-mutant gemistocytic astrocytomas.

===== Imaging =====

There are no imaging characteristics that can differentiate this subtype of diffuse astrocytoma.

===== Prognosis =====

Gemistocytic astrocytomas tend to dedifferentiate earlier and have a worse outcome, but this will require confirmation in comparison to cohorts with known IDH mutation status.
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Two [[diffuse astrocytoma]] variants have been deleted from the [[WHO classification]] [[2016]]: [[protoplasmic astrocytoma]], a diagnosis that was previously defined in only vague terms and is almost never made any longer given that tumors with this histological appearance are typically characterized as other more narrowly defined lesions; and [[fibrillary astrocytoma]], since this diagnosis overlaps nearly entirely with the standard [[diffuse astrocytoma]]. As a result, only [[gemistocytic astrocytoma]] remains as a distinct variant of [[diffuse astrocytoma IDH mutant]].