CNS tumor
Diffuse astrocytic and oligodendroglial tumors
Gemistocytic astrocytoma IDH mutant
Author: Eman Abdelzaher, M.D., Ph.D.
Topic Completed: 1 February 2018
Minor changes: 4 September 2020
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: Gemistocytic astrocytoma IDH-mutant
Table of Contents
Definition / general | Epidemiology | Sites | Grading | Prognostic factors | Gross description | Microscopic (histologic) description | Positive stains | Molecular / cytogenetics description | Differential diagnosisCite this page: Abdelzaher E. Gemistocytic astrocytoma IDH mutant. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cnstumorgemistocyticastrocytomaIDHmut.html. Accessed August 4th, 2021.
Definition / general
- Variant of IDH mutant diffuse astrocytoma characterized by the presence of a recognizable population of neoplastic gemistocytes (> 20%)
Epidemiology
- Accounts for approximately 10% of all WHO grade II diffuse astrocytomas
- Age: fourth decade
- Appears more frequently in men
Sites
- Any region of the CNS
- Most commonly affects the frontal and temporal lobes
Grading
- WHO grade II
Prognostic factors
- Gemistocytic astrocytoma has been associated with early progression and less favorable outcome
- However, it remains to be determined whether the prognosis of IDH mutant gemistocytic astrocytoma differs significantly from that of IDH mutant diffuse astrocytoma
Gross description
- Similar to other low grade diffuse gliomas
- May have single, large, smooth walled cyst
Microscopic (histologic) description
- Conspicuous proportion of neoplastic gemistocytes (> 20%)
- Neoplastic gemistocytes are angular shaped with abundant, glassy, eosinophilic cytoplasm and eccentric nuclei with distinct nucleoli
- There is a coarse fibrillary background formed by stout cytoplasmic processes
- Intermingled small cell component: small tumor cells with dark nuclei and scanty cytoplasm; constitutes the proliferating component with higher Ki67 index compared to gemistocytic cells
- Perivascular lymphocyte cuffing is common
- Rare or no mitoses
Positive stains
Molecular / cytogenetics description
- Mutations in IDH genes
- High frequency of p53 mutations
Differential diagnosis
- Ganglioglioma: neoplastic ganglion cells
- Gliosis: evenly distributed hypertrophic astrocytes, IDH1 negative
- Subependymal giant cell astrocytoma: intraventricular, noninfiltrative
