Diffuse astrocytoma grading

Diffuse astrocytomas can be graded in according to a number of systems, the most popular being the WHO grading system. In general these grading systems focus on the presence or absence of a number of histological features :

  • cellular atypia/anaplasia 
  • mitotic activity
  • microvascular proliferation
  • necrosis typically with perinecrotic palisading

The most commonly used grading systems are:  

Direct equivalence between the grades of various grading systems is of course not possible (otherwise they wouldn't be different systems), and thus care should be taken to state which system is being used .

It is well recognized that pathological classification has a high interobserver variation and thus imperfectly predicts clinical outcomes .

Recent studies have shown that the genetic status of these tumors are more reflective of their subtypes than the histologic grading (please refer on isocitrate dehydrogenase 1 - IDH1 for a broad discussion on this topic) .