title: Diagnostic challenges, management and outcomes of midline low-grade gliomas.
abstract: BACKGROUND
  Low-grade gliomas (LGGs) are slow-growing and diffusely infiltrating tumours constituting 25-30 % of adult gliomas. Rarely, these tumours may arise in the cerebral midline, including the thalamus, hypothalamus, tectum and brainstem. Here we present a contemporary experience with midline LGGs.
  
  
  METHODS
  Midline LGGs were identified from a retrospective database of adult patients who received a histological diagnosis of WHO grade II glioma between 2006 and 2012 at a single institution. Location, radiological data and clinical outcomes were collected. IDH1 status was assessed by immunohistochemistry.
  
  
  RESULTS
  Eighteen patients with midline LGGs were identified, with a median age of 45. Most received biopsy upon diagnosis, though asymptomatic patients with tectal tumours underwent active surveillance. Oligodendroglial tumours were much less common than in a comparable group of lobar tumours (6 vs. 38 %, Fisher's exact test, p = 0.007). Only one tumour was immunopositive for IDH1 (1/17). Radiological diagnosis correlated with histology in only 71 % of patients. Median survival of midline LGGs was 48 months (3-90 months) and radiological features such as contrast enhancement, size and radiological diagnosis did not predict survival in this cohort. Median overall survival of midline LGGs was less than lobar LGGs (log-rank, p = 0.006), though differences became insignificant when considering only biopsied astrocytomas in both locations (log-rank, p = 0.491).
  
  
  CONCLUSIONS
  Diagnosis of midline LGGs is complicated by both limitations of biopsy and imaging. Midline tumours have a poorer prognosis compared to lobar equivalents and survival differences are probably due to the absence of significant surgical intervention in midline locations.
authors.affiliation: School of Medicine, University of Liverpool, Cedar House Ashton Street, Liverpool, L9 7AL, UK, md0u92dd@liv.ac.uk.
authors.forename: Mueez
authors.initials: M
authors.lastname: Waqar
authors.forename: Shahid
authors.initials: S
authors.lastname: Hanif
authors.forename: Nitika
authors.initials: N
authors.lastname: Rathi
authors.forename: Kumar
authors.initials: K
authors.lastname: Das
authors.forename: Rasheed
authors.initials: R
authors.lastname: Zakaria
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Brodbelt
authors.forename: Carol
authors.initials: C
authors.lastname: Walker
authors.forename: Michael D
authors.initials: MD
authors.lastname: Jenkinson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000401:mortality* / Q000628:therapy; D003131:Combined Modality Therapy; D019468:Disease Management; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D005910:Glioma / Q000175:diagnosis* / Q000401:mortality* / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D012189:Retrospective Studies; D015996:Survival Rate; D055815:Young Adult
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