Edit Article

Dysembryoplastic neuroepithelial tumour

contributed by Dr Frank Gaillard on May 2, 2008

System: Central Nervous System
Tag: neoplasm

A dysembryoplastic neuroepithelial tumour (DNET) is a benign (WHO Grade I) slow growing tumour arisig from either cortical (vast majority) or deep grey matter. They are thought to arise from secondary germinal layers and are frequently (up to 80% of cases) associated with co-existent cortical dysplasia, and is characteristically the cause of intractable partial seizures (see temporal lobe epilepsy). 

They demonstrate essentially no growth over time, although very gradual increase in size has been described. As expected prognosis is excellent and even though these lesions are often incompletely resected, tumour progression is uncommon. Additionally even in cases of incomplete ressection, seizures frequently cease. 

Location

The temporal lobe is the most common location, but all parts of the CNS containing grey matter are potential locations. 

Radiographic Features

CT
  • if cortical may scallop the inner table of of the skull vault (44 - 60%)
  • calcification in 20 - 40% (more common histologically) 
  • low density
  • no enhancement
MRI

Typically seen as a cortical lesion with hardly any surrounding vasogenic oedema 

  • T1 : generally low signal
  • T2 : generally high signal with high signal 'bubbly appearance'
  • FLAIR : mixed signal intensity with bright rim sign. (see case 2)
  • GE (gradient echo) : haemosiderin staining uncommon as bleeding into DNETs is only occasional ; calcification is not infrequent
  • SWI :  areas of signal drop out may be seen. 
  • C+ GAD : may show enhancement in ≈ 1/3 of cases 5 
  • DWI : no restricted diffusion
  • MRS : non-specific although lactate may be present

Differential diagnoses

The differential diagnosis will depend on the location of the tumour. 

Mesial temporal lobe

see also temporal lobe tumours

Cortical