title: Diffusion-weighted MRI: distinction of skull base chordoma from chondrosarcoma.
abstract: OBJECTIVE
  Chordoma and chondrosarcoma of the skull base are rare tumors with overlapping presentations and anatomic imaging features but different prognoses. We hypothesized that these tumors might be distinguished by using diffusion-weighted MR imaging.
  
  
  METHODS
  We retrospectively reviewed 19 patients with pathologically confirmed chordoma or chondrosarcoma who underwent both conventional and diffusion-weighted MR imaging. Differences in distributions of ADC were assessed by the Kruskal-Wallis test. Associations between histopathologic diagnosis and conventional MR imaging features (T2 signal intensity, contrast enhancement, and tumor location) were assessed with the Fisher exact test.
  
  
  RESULTS
  Chondrosarcoma was associated with the highest mean ADC value (2051 ± 261 × 10(-6) mm(2)/s) and was significantly different from classic chordoma (1474 ± 117 × 10(-6) mm(2)/s) and poorly differentiated chordoma (875 ± 100 × 10(-6) mm(2)/s) (P < .001). Poorly differentiated chordoma was characterized by low T2 signal intensity (P = .001), but other conventional MR imaging features of enhancement and/or lesion location did not reliably distinguish these tumor types.
  
  
  CONCLUSIONS
  Diffusion-weighted MR imaging may be useful in assessing clival tumors, particularly in differentiating chordoma from chondrosarcoma. A prospective study of a larger cohort will be required to determine the value of ADC in predicting histopathologic diagnosis.
authors.affiliation: Department of Radiology, Stanford University, Palo Alto, California 94304, USA. kyeom@stanford.edu
authors.forename: K W
authors.initials: KW
authors.lastname: Yeom
authors.forename: R M
authors.initials: RM
authors.lastname: Lober
authors.forename: B C
authors.initials: BC
authors.lastname: Mobley
authors.forename: G
authors.initials: G
authors.lastname: Harsh
authors.forename: H
authors.initials: H
authors.lastname: Vogel
authors.forename: R
authors.initials: R
authors.lastname: Allagio
authors.forename: M
authors.initials: M
authors.lastname: Pearson
authors.forename: M S B
authors.initials: MS
authors.lastname: Edwards
authors.forename: N J
authors.initials: NJ
authors.lastname: Fischbein
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002648:Child; D002675:Child, Preschool; D002813:Chondrosarcoma / Q000473:pathology*; D002817:Chordoma / Q000473:pathology*; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019292:Skull Base Neoplasms / Q000473:pathology*; D055815:Young Adult