9421/1 Piloid astrocytoma


Related terms

Pilocytic astrocytoma

Definitions

Tumours of the central nervous system
ICD-O-3 topography code: C70, C71 and C72

Pilocytic astrocytoma is the most common glioma in children and adolescents. It is a generally circumscribed, slowly growing, often cystic astrocytoma with preferential location in the cerebellum and cerebral midline structures (optic pathways, hypothalamus, brain stem) 1
 
Louis DN, Ohgaki H, Wiestler OD, Cavenee WK (Eds.)
WHO Classification of Tumours of the Central Nervous System.
4th Edition
International Agency for Research on Cancer: Lyon 2007



. Histologically, it is characterized by a biphasic pattern with varying proportions of compacted bipolar cells with Rosenthal fibers and loose textured multipolar cells with microcysts and granular bodies 2
 
Burger PC, Scheithauer BW, Vogel F.S.
Surgical Pathology of the Nervous System and Its Coverings
4th Edition,
Churchill Livingston: London 2002



. Since surgery can be curative, pilocytic astrocytoma corresponds to WHO grade I 3
 
Louis DN, Ohgaki H, Wiestler OD, Cavenee WK (Eds.)
WHO Classification of Tumours of the Central Nervous System.
4th Edition
International Agency for Research on Cancer: Lyon 2007



; however, in some locations (optic pathways, hypothalamus) complete resection is usually not possible.
Genetically, pilocytic astrocytomas are chracterized by the presence of NF1 mutations, BRAF duplications and the absence of IDH1 mutations
4
Click to access Pubmed
Korshunov A, Meyer J, Capper D, Christians A, Remke M, Witt H, Pfister S, von Deimling A, Hartmann C (2009)
Combined molecular analysis of BRAF and IDH1 distinguishes pilocytic astrocytoma from diffuse astrocytoma.
Acta Neuropathol 118: 401-5



.

Pilocytic astrocytomas, in particular those involving the optic pathways, are a hallmark of the autosomal dominant syndrome neurofibromatosis type 1 (NF1) .

> Pilomyxoid astrocytoma is considered a variant of pilocytic astrocytoma.