Definition and diagnostic implications of gemistocytic astrocytomas: a pathological perspective.

Gemistocytic astrocytoma still continues to be enigmatic; both in terms of definition and prognostic implications. The major issue of contention has been the clinical relevance of this pathological entity. The currently accepted definition of gemistocytic astrocytoma requires 20% or more gemistocytes, and considers the neoplasm as a diffuse astrocytoma, which is a WHO grade II tumor. Some suggest that gemistocytic morphology should be considered as evidence of a higher grade astrocytoma. However, there is no consensus on the percentage of gemistocytes associated with a worse prognosis than otherwise expected. Given the reported cases and series, it is not clear that this morphology portends a more aggressive biology when all else is equal. There is still a need for studies with sufficient numbers of well-matched gemistocytic and non-gemistocytic astrocytic neoplasms to decide whether upgrading a tumor with 'significant' number of gemistocytes is justifiable. This article presents a critical review of the existing studies and a brief mention of our experience from a pathological perspective.