title: Pilocytic astrocytomas: well-demarcated magnetic resonance appearance despite frequent infiltration histologically.
abstract: OBJECTIVE
  To determine the magnetic resonance imaging (MRI) characteristics of pilocytic astrocytomas and to correlate them with the histopathologic findings.
  
  
  METHODS
  MRI examinations and histopathologic findings in 56 patients with pilocytic astrocytomas were retrospectively reviewed. In 38 patients, findings on MRI were compared with those on computed tomography.
  
  
  RESULTS
  The tumors occurred at all levels of the central nervous system, including the spinal cord. The intracranial tumors were periventricular (73%) or periaqueductal (9%). All tumors were typical pilocytic astrocytomas and were grade 1 on the basis of the World Health Organization classification. At operation, they were often circumscribed and cystic. Radiologically, the tumors were well demarcated (96%), had benign morphologic features, and almost always showed enhancement (94%).
  
  
  CONCLUSIONS
  MRI of pilocytic astrocytomas typically demonstrated a relatively large, sharply demarcated periventricular mass with pronounced contrast enhancement but minimal or no associated edema. Often, the tumors were cystic on MRI. Despite the well-demarcated appearance grossly and on MRI, pathologic review showed that many of these tumors (64%) infiltrated the surrounding parenchyma, particularly the white matter.
authors.affiliation: Department of Diagnostic Radiology, Mayo Clinic Rochester, Minnesota 55905, USA.
authors.forename: K J
authors.initials: KJ
authors.lastname: Coakley
authors.forename: J
authors.initials: J
authors.lastname: Huston
authors.forename: B W
authors.initials: BW
authors.lastname: Scheithauer
authors.forename: G
authors.initials: G
authors.lastname: Forbes
authors.forename: P J
authors.initials: PJ
authors.lastname: Kelly
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001254:Astrocytoma / Q000000981:diagnostic imaging / Q000473:pathology*; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed