be either enhancing or non-enhancing. Less frequently, there can be a necrotic mass with a central non-enhancing zone or a predominantly solid mass with minimal or no cyst-like component. The precise cause for the often-noted enhancement of the cyst wall is not well understood and does not seem to correlate with aggressiveness of the lesion or prognosis.
       Macroscopically, as would be anticipated from the imaging features described above, these tumors are typically well-circumscribed cyst-like masses with a discrete mural nodule. Histologically, these lesions demonstrate a ‘biphasic pattern’. Rosenthal fibers as well as microcysts are often present. It should also be noted that the relative contribution of the loose and compact tissue components is highly variable within different tumors. While macroscopically well circumscribed, there may in fact be microscopic invasion into surrounding brain parenchyma, but this has not been shown to affect long-term prognosis.
 
Therapy and Prognosis
     Surgical management is the treatment of choice for pilocytic astrocytomas. Total resection

Figure 3: A, Sagittal T1 pre-contrast. B, FLAIR image demonstrates that contents of cyst are hyperintense to CSF. C, Sagittal T1-post gadolinium injection demonstrates homogeneous enhancement of the mural nodule. D, CoronalT1-post gadolinium.

References
(1) Bell D et al, “Pilocytic astrocytoma of the adult-clinical features, radiological features and management.” Br J Neurosurg. 2004 Dec;18(6):613-6.
(2) Burkhard C et al, “A population-based study of the incidence and survival rates in patients with pilocytic astrocytoma”, J Neurosurg. 2003 Jun;98(6):1170-4.
(3) Koeller KK & Rushing EJ, From the Archives of the AFIP: Pilocytic Astrocytoma: “Radiologic-Pathologic Correlation” RadioGraphics 2004; 24: 1693-1708.