title: Cellularity and apparent diffusion coefficient in oligodendroglial tumours characterized by genotype.
abstract: OBJECTIVE
  Apparent diffusion coefficient (ADC) describes water diffusion within tissues. Previous studies report a negative linear correlation between minimum ADC and tumour cellularity in different types of gliomas, but there are no studies in oligodendroglial tumours. This study evaluated the relationship between ADC and tumour cellularity in oligodendroglial tumours characterized by genotype.
  
  
  METHODS
  ADC was assessed in 17 patients with known 1p/19q status: 3 grade II oligodendrogliomas (OII), 9 grade II oligoastrocytomas (OAII), 5 grade III oligoastrocytomas (OAIII). Regions of interest were placed on ADC maps around tumour margins to generate mean tumour ADC, and over minimum and maximum tumour ADC. Histopathology assessment of tumour cellularity determined minimum, maximum and mean cell density in serial stereotactic biopsies.
  
  
  RESULTS
  1p/19q loss was present in 2/3 OII, 5/9 OAII, 2/5 OAIII. Grade III tumours had higher maximum cell density than grade II tumours (17.2 vs. 10.57%: Mann Whitney U; P = 0.20). Oligoastrocytoma were more likely to have a lower minimum cell density than oligodendrogliomas (Mann Whitney U; P = 0.032). There was no relationship between cell density and genotype. There was no linear correlation between mean ADC and mean cell density (Spearman's rho; r = 0.486: P = 0.438), minimum ADC and maximum cell density (Spearman's rho; r = 0.158: P = 0.660), and maximum ADC and minimum cell density (Spearman's rho; r = 0.039: P = 0.985).
  
  
  CONCLUSIONS
  In oligodendroglial tumours there is no relationship between quantitative assessment of cellularity and ADC. This may reflect differences in oligodendroglial tumour biology compared to other gliomas, although the composition of the extracellular matrix may influence ADC more than cellularity.
authors.affiliation: Department of Neurosurgery, The Walton Centre for Neurology and Neurosurgery, Lower Lane, Liverpool, L9 7LJ, UK. michael.jenkinson@liv.ac.uk
authors.forename: Michael D
authors.initials: MD
authors.lastname: Jenkinson
authors.forename: Daniel G
authors.initials: DG
authors.lastname: du Plessis
authors.forename: Trevor S
authors.initials: TS
authors.lastname: Smith
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Brodbelt
authors.forename: Kathy A
authors.initials: KA
authors.lastname: Joyce
authors.forename: Carol
authors.initials: C
authors.lastname: Walker
mesh_terms: D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000235:genetics / Q000473:pathology*; D002878:Chromosomes, Human, Pair 1; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D005838:Genotype; D006801:Humans; D019656:Loss of Heterozygosity; D008297:Male; D008875:Middle Aged; D009837:Oligodendroglioma / Q000235:genetics / Q000473:pathology*; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D055815:Young Adult