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Pilocytic Astrocytoma (PA)

Last Updated: October 1, 2018

Figure 1: This posterior fossa pilocytic astrocytoma (PA) has a large cyst with an adjacent mass (nodule). The axial image (left) shows that this patient's cytic tumor is compressing and deviating the fourth ventricle with resulting hydrocephalus. Sagittal postcontrast T1WI image (right) shows the sometimes very heterogeneous enhancement apparent in the solid portion of the lesion that belies its underlying low-grade histology.

 

Figure 2: Axial (top row left) and sagittal (top row right) post-contrast T1-weighted images demonstrate a cystic lesion with a brightly enhancing mural nodule/mass. This appearance is very typical for juvenile pilocytic astrocytoma, but must be distinguished from the similar-appearing hemangioblastoma when in the posterior fossa, particularly when in older...