Purpose or Case Report: The purpose of this pictorial review is
* To illustrate the classic MRI characteristics of PA in common and less typical locations in both standard advanced MRI sequences. Special attention to MR Spectroscopy will be provided
* To outline the less specific imaging features
* To discuss the relevant differential diagnosis according to tumor location
Methods & Materials: Pilocytic Astrocytoma (PA) is the most common pediatric glial tumor, typically located in he posterior fossa with predilection to the cerebellum. Other common locations are along the hypothalamic pituitary axis, optic nerves and chiasm. The association with neurofibromatosis (NF1) is well established, known to affect mainly the optic pathways. Supratentorial and spinal cord location are not often seen in pediatric population.

The classic radiologic appearance of cystic lesion with avidly enhancing mural nodule makes potential easy diagnosis. Nevertheless, less specific features are also known and include necrotic mass, hemorrhagic change, predominantly solid lesion, aggressive local invasion and leptomeningeal spread.
The treatment of choice is surgical resection providing excellent outcome. Chemotherapy and radiotherapy are reserved for compromising tumor location and disseminated disease.

Results: This presentation will demonstrate the imaging features of PA in the posterior fossa, pituitary axis and optic pathways as well as less common imaging characteristics and locations like brain stem, cerebral hemispheres and with leptomeningeal dissemination.
Relevant differential options including high grade glioma, germ cell tumours and hemangioblastoma will be discussed.
Conclusions: PA is a common pediatric CNS tumor and usually easily diagnosed with the classis imaging features of cystic mass with enhancing mural nodule. Familiarity with the spectrum of imaging characteristics will facilitate diagnosis and appropriate treatment option.