title: Distinctive MRI features of pediatric medulloblastoma subtypes.
abstract: OBJECTIVE
  We hypothesized that the apparent diffusion coefficient (ADC) and other MRI features can be used to predict medulloblastoma histologic subtypes, as defined by the World Health Organization (WHO) in WHO Classification of Tumours of the Central Nervous System.
  
  
  METHODS
  A retrospective review of pediatric patients with medulloblastoma between 1989 and 2011 identified 38 patients with both pretreatment MRI and original pathology slides. The mean and minimum tumor ADC values and conventional MRI features were compared among medulloblastoma histologic subtypes.
  
  
  RESULTS
  The cohort of 38 patients included the following histologic subtypes: 24 classic medulloblastomas, nine large cell (LC) or anaplastic medulloblastomas, four desmoplastic medulloblastomas, and one medulloblastoma with extensive nodularity. The median age at diagnosis was 8 years (range, 1-21 years) and the median follow-up time was 33 months (range, 0-150 months). The mean ADC (× 10(-3) mm(2)/s) was lower in classic medulloblastoma (0.733 ± 0.046 [SD]) than in LC or anaplastic medulloblastoma (0.935 ± 0.127) (Mann-Whitney test, p = 0.004). Similarly, the minimum ADC was lower in classic medulloblastoma (average ± SD, 0.464 ± 0.056) than in LC or anaplastic medulloblastoma (0.630 ± 0.053) (p = 0.004). The MRI finding of focal cysts correlated with the classic and desmoplastic subtypes (Fisher exact test, p = 0.026). Leptomeningeal enhancement positively correlated with the LC or anaplastic medulloblastoma subtype and inversely correlated with the classic medulloblastoma and desmoplastic medulloblastoma subtypes (p = 0.04). Ring enhancement correlated with tumor necrosis (p = 0.022) and with the LC or anaplastic medulloblastoma histologic subtype (p < 0.001).
  
  
  CONCLUSIONS
  The LC or anaplastic medulloblastoma subtype was associated with increased ADC and with ring enhancement, the latter of which correlated with tumor necrosis. These features could be considered in the evaluation of high-risk medulloblastoma subtypes.
authors.affiliation: Department of Radiology, Lucile Packard Children's Hospital, Stanford University, 725 Welch Rd, Pediatric MRI & CT, Rm 0511, Palo Alto, CA 94304, USA. kyeom@stanford.edu
authors.forename: Kristen W
authors.initials: KW
authors.lastname: Yeom
authors.forename: Bret C
authors.initials: BC
authors.lastname: Mobley
authors.forename: Robert M
authors.initials: RM
authors.lastname: Lober
authors.forename: Jalal B
authors.initials: JB
authors.lastname: Andre
authors.forename: Sonia
authors.initials: S
authors.lastname: Partap
authors.forename: Hannes
authors.initials: H
authors.lastname: Vogel
authors.forename: Patrick D
authors.initials: PD
authors.lastname: Barnes
mesh_terms: D000293:Adolescent; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000473:pathology; D016009:Chi-Square Distribution; D002648:Child; D002675:Child, Preschool; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007223:Infant; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008527:Medulloblastoma / Q000175:diagnosis* / Q000473:pathology; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D055815:Young Adult
chemical_list: D003287:Contrast Media