Answer and Discussion of Quiz Set: N-019

1.    Which of the following features is seen in diffuse astrocytoma (WHO grade II)?

A.  Mitotic count of over 3 per high-power field

B.  Proliferation of endothelial cells (endothelial proliferation)

C.  Enhancement on MRI

D.  Mass effect and herniation

E.  Tumor growth across the midline through the corpus callosum

Answer and Discussion: The answer is (D). Three or more mitotic count per 10 high-power field is too high for a WHO grade II astrocytoma and suggests a diagnosis of anaplastic astrocytoma (WHO grade III). Proliferation of endothelial cells meets the criteria of a glioblastoma (WHO grade IV). However, it should be noted that vascular proliferation can occasionally be seen in pilocytic astrocytoma (WHO grade I). All clinical and histologic features should be taken into account when a diagnosis is made. WHO grade II gliomas usually do not enhance and do not grow accross the corpus callosum. Although diffuse astrocytoma is a low-grade (WHO grade II) tumor, it can grow to a large size that would cause mass effects, deviation of the midline, and herniation.