Department of Pathology, University of Oklahoma Health Sciences Center

Pilocytic Astrocytoma (WHO grade I/IV)

Panel A and B (T1-weighed contrast enchancing image): 

• Similar to this case, a significant proportion of pilocytic astrocytoma occur in the cerebellum. 

• The tumor is large in this patient and produces mass effect with compression of the aqueduct leading to hydrocephalus.

•  Pilocytic astrocytomas, particularly the larger ones, often have cystic components and mural nodules. 

• Although most high-grade glial neoplasms (WHO grade III and IV) enhance and low-grade glial neoplasm (WHO grade II) do not, pilocytic astrocytoma (WHO grade I) is an exception and enhancement is the rule. 

• Peritumoral edema may be present but is usually not a prominent in pilocytic astrocytomas. Peritumoral edema is best visualized in T2-weighed images. 

Panel C (T1-weighed contrast enchancing image): This sagittal image well demonstrated the compression of the aqueduct by the tumor leading to hydrocephalus (dilated lateral ventricles).

Panel D (Fluid attenuation and image reversion image, FLAIR): Mild hydrocephalus resulted from compression of the aqueduct by the tumor is well demonstrated in this FLAIR image. 

Images courtesy of Dr. Kalliopi Petroulou, University of Oklahoma Health Science Center. 

For Comment: KarMing-Fung@ouhsc.edu