Pilocytic astrocytoma

General characteristics

The pilocitic astrocytoma is more common in children, is infratentorial, and represents a cyst (an asterisk in Fig.29) with a parietal node (the head of the arrow in Fig. 1). Less common in adults, mainly in the form of solid formation and is located supratentorial (head arrow in Fig. 2).

1

Fig. 1

2

Fig. 2

Epidemiology

0.6-5.1% of all tumors of the central nervous system, 6% of tumors of the central nervous system of childhood, 80% of all cerebellar astrocytomas, a peak occurrence of 5-15 years.

Morphology

There are three different types of morphological structure:

  • a cyst with a parietal node (the most common form), this form is most typical for infratentorial localization and is found mainly in children
  • solid formation
  • cystic and solid formation.

On the MRI cyst ↑ T2 and ↑ Flair ↓ T1, and a solid component → in T2 and T1 of the brain substance.

The cyst wall usually consists of a healthy cerebellar tissue, much less often of a tumor tissue.

Calcinates are found in 11% of cases, and vasogenic edema - in 5%.

On the CT scan, the contents of the cyst → cerebrospinal fluid, and the structure of the solid part → cerebral.

Hemorrhages and necrosis are not characteristic.

3

Fig. 3

Tumor cyst in the left hemisphere of the cerebellum (arrowheads in Fig. 3), the contents of the cyst have ↑ MR-signal by Flair in comparison with the unchanged cerebrospinal liquor (asterisk in Fig. 3). The parietal node on the inner side of the cyst wall (arrow in Fig. 3).



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