Gemistocytic astrocytoma

Gemistocytic astrocytoma is a histologic subtype of low grade astrocytoma, with a poorer prognosis than other matched WHO grade tumors, and with no specific imaging features. 

For a general discussion of clinical presentation, epidemiology, treatment please refer to the article on low grade astrocytomas. 

Pathology

Gemistocytic astrocytomas are characterized by a significant gemistocytes population, which are large cells with their cytoplasm filled with eosinophilic material displacing the nucleus eccentrically ¹.

It is important to note that other gliomas (e.g. fibrillary astrocytoma and oligodendrogliomas) can have occasional gemistocytes, without being designated a gemistocytic astrocytoma. Some authors use a cut off of 20% of the tumor cells being gemistocytes before designating it as a gemistocytic astrocytoma ^1-2. 

Radiographic features

Although there are no specific features which allow pre-biopsy diagnosis, gemistocytic astrocytomas are almost always supratentorial and usually located in the frontal lobes ⁴. 

Treatment and prognosis

In general gemistocytic astrocytomas, although often still considered WHO II tumors, have a more aggressive behavior compared to fibrillary astrocytomas ^1-3. Some authors suggest that they should be considered WHO III tumors ².  

The median with treatment is only 2.5 years, with a 5-year survival rate of 30% which is significantly worse than other low grade gliomas ⁴. Older age at presentation appears to be a poor prognostic sign ⁴. 

Given the generally worse prognosis, most clinicians would favor a more aggressive approach to treatment.