title: Diagnostic challenges of primary thalamic gliomas-identification of a minimally enhancing neuroradiological subtype with aggressive neuropathology and poor clinical outcome.
abstract: OBJECTIVE
  To evaluate neuropathology and neuroradiology in the diagnosis and clinical outcome of a retrospective cohort of thalamic gliomas.
  
  
  METHODS
  Neuropathological and neuroradiological review was undertaken in 25 cases of radiologically suspected thalamic glioma (excluding childhood pilocytic astrocytoma) over an 8 year period (2004-2012) at Frenchay Hospital and compared to the clinical outcome.
  
  
  RESULTS
  In 12/25 (48%) there was a difference in neuropathological and suspected neuroradiological grading of the lesion of one or more grades. In 5/12 (42%) cases, the neuroradiology was lower grade than the pathology. In 4/5 (80%) of these cases, we identified a minimally enhancing subtype where the neuroradiology was predicted to be of lower grade than neuropathology. In 4/12, (33%) the suspected neuroradiology grade was higher than the final pathology. In 3/4, (75%) of these cases the suspected neuroradiology grade was higher than the neuropathology possibly because of unusual differentiation within the thalamic glioma (central neurocytoma, anaplastic oligoastrocytoma, and diffuse astrocytoma with pilocytic features). In 3/12 (25%) the biopsy was non-diagnostic. Neuropathology was a better predictor of clinical outcome than neuroradiology. 9/10 (90%) WHO Grade 4 gliomas and 8/9 (88%) Grade 3 gliomas on neuropathology were dead between 3-7 years after diagnosis. 3/3 (100%) Grade 2 gliomas on neuropathology were alive 3-7 years after diagnosis. 2/3 (67%) of the non-diagnostic cases were alive 3-7 years after biopsy. In 1/3 (33%) of the non-diagnostic cases the outcome was unknown.
  
  
  CONCLUSIONS
  Diagnosis of primary thalamic glioma is challenging. We have identified that in the thalamus, a pattern of diffuse infiltration with minimal enhancement on imaging may often represent high-grade glioma. Neuropathology is overall the best predictor of clinical outcome.
authors.affiliation: Department of Neuropathology, Frenchay Hospital, Bristol, UK, kathreena.kurian@nbt.nhs.uk.
authors.forename: K M
authors.initials: KM
authors.lastname: Kurian
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: H R
authors.initials: HR
authors.lastname: Haynes
authors.forename: N A
authors.initials: NA
authors.lastname: Macaskill
authors.forename: M
authors.initials: M
authors.lastname: Bradley
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000145:classification / Q000473:pathology*; D002648:Child; D003937:Diagnosis, Differential; D005260:Female; D005910:Glioma / Q000145:classification / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D009485:Neuroradiography / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013788:Thalamus / Q000473:pathology*; D055815:Young Adult