title: Imaging findings in primary intracranial atypical teratoid/rhabdoid tumors.
abstract: BACKGROUND
  Intracranial atypical teratoid/rhabdoid tumors (AT/RT) are rare and extremely aggressive neoplasms seen primarily in childhood. Imaging features are often considered non-specific. However, correct diagnosis of AT/RT is important because these tumors have a markedly different clinical prognosis and require more aggressive therapy.
  
  
  OBJECTIVE
  To determine the imaging features of AT/RT.
  
  
  METHODS
  We retrospectively analyzed imaging findings in 11 patients with primary intracranial AT/RT presenting over a period of 5 years. CT (n=11), MR (n=7), clinical (n=11) and pathological (n=11) features were evaluated. FISH analysis showing monosomy of chromosome 22 (absence of bcr 22q11 locus) was available for three patients. Immunohistochemical staining for INI-1 (BAF47) was performed on all tumors.
  
  
  RESULTS
  There were 11 patients, 6 boys and 5 girls. The age of presentation varied from 1 month to 15 years (average age 3 years 8 months). Six tumors were located in the posterior fossa and five in the supratentorial compartment. The tumors showed a hyperdense solid component (64%) that showed moderate to marked enhancement with contrast medium. On MR imaging, the predominant signal pattern was isointensity on T1-weighted images (57%) and T2 shortening with heterogeneity on T2-weighted images (86%). All tumors were large in size (average 4.2 x 3.7 cm), and there was a tendency for calcification (36%), hemorrhage (46%), necrosis (46%) and perifocal edema (100%). There was also a high tendency for subarachnoid dissemination, with five patients (46%) demonstrating brain and/or spinal metastasis. At follow-up (n=7), six patients showed local recurrence. At the time of recurrence, all these patients showed extensive leptomeningeal spread of the disease in both intracranial and intraspinal compartments.
  
  
  CONCLUSIONS
  There are no specific imaging features for intracranial AT/RT. But a high tendency toward large size, a hyperdense solid component on CT scan with calcification, hemorrhage, necrosis and subarachnoid spread suggest that this tumor should be considered in the differential diagnosis of large pediatric intracranial tumors.
authors.affiliation: Department of Diagnostic Imaging, The Hospital for Sick Children, 555 University Ave., Toronto, Ontario M5G 1X8, Canada.
authors.forename: Hemant
authors.initials: H
authors.lastname: Parmar
authors.forename: Cynthia
authors.initials: C
authors.lastname: Hawkins
authors.forename: Eric
authors.initials: E
authors.lastname: Bouffet
authors.forename: James
authors.initials: J
authors.lastname: Rutka
authors.forename: Manohar
authors.initials: M
authors.lastname: Shroff
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging; D008297:Male; D018242:Neuroectodermal Tumors, Primitive / Q000175:diagnosis*; D012189:Retrospective Studies; D018335:Rhabdoid Tumor / Q000175:diagnosis* / Q000473:pathology; D012886:Skull / Q000000981:diagnostic imaging / Q000473:pathology*; D013724:Teratoma / Q000175:diagnosis* / Q000473:pathology; D014057:Tomography, X-Ray Computed