angiocentric glioma

Angiocentric gliomas are rare superficial slow-growing brain tumors typically presenting in young patients with intractable partial epilepsy . They were first introduced in the 2007 (4) edition of the WHO brain tumor classification, and are classified as WHO grade I tumors .

For a general discussion of clinical presentation, epidemiology, and treatment, please refer to the article on low-grade astrocytomas.

Epidemiology

Angiocentric gliomas are very rare tumors with relatively few reported cases. They usually affect children and young adults . No reported gender predilection has been reported .

Clinical presentation

Seizures are the classical presentation, with over 95% of patients presenting with intractable seizures .

Pathology

Angiocentric gliomas are designated as WHO grade I tumors . The exact etiology of angiocentric gliomas remains unclear although some features are similar to ependymomas . In fact, sometimes, a distinct ependymoma component may co-exist .

Microscopic appearance

These tumors demonstrate a monomorphic population of elongated spindle-shaped bipolar cells with a strikingly perivascular orientation, somewhat reminiscent to perivascular pseudorosettes . Although tumor cells do extend into the surrounding parenchyma, a strong predilection for perivascular spread is evident . Subpial growth along the surface of the cortex is also a prominent feature .

Immunophenotype

The immunophenotype shares some similarities to ependymomas .

• GFAP: positive
• EMA: both surface and perinuclear cytoplasmic dot may be present

Ki-67 index is usually <5% .

They do not demonstrate neuronal markers (e.g. synaptophysin, chromogranin-A, neuronal nuclear antigen) and they are isocitrate dehydrogenase (IDH) negative.

Associations

Cortical dysplasia may be associated.

Radiographic features

Angiocentric gliomas are usually cortical or subcortical (grey-white matter junction), typically well-delineated, supratentorial tumors that tend to expand affected gyri. They exhibit a propensity to spread horizontally in the subpial plane and deeply along vessels .

CT

Typically appear as an expansile non-enhancing cortical tumor.

MRI 

• T1
  • hypointense
  • hyperintense rim may be seen
• T2 / FLAIR
  • hyperintense
  • extension toward the ventricles along vessels
  • may have cystic-appearing areas
• T1 C+ (Gd): no enhancement

History and etymology

Angiocentric glioma was initially identified in 2005 in two separate case reports and then introduced in the WHO classification of CNS tumors in 2007. It remains an entity in the current (2016) WHO classification .

Differential diagnosis

Given their rarity, on purely imaging grounds it is difficult to distinguish these tumors from more common diffuse gliomas (both astrocytoma and oligodendroglioma). Other imaging differential considerations include:

• focal cortical dysplasia
• cortical tuber (forme fruste of tuberous sclerosis)
• DNET 
  • "bubbly" cortical and subcortical lesion
  • rim of high signal on FLAIR
  • minimal surrounding edema
• perivascular spaces
  • total nulling on the FLAIR sequence
• ganglioglioma/gangliocytoma
  • usually enhance
  • well defined
• multinodular and vacuolating neuronal tumors
  • subcortical cluster of cystic-like lesions

Siehe auch:

• Gangliogliom
• Oligodendrogliom
• Dysembryoplastischer neuroepithelialer Tumor

und weiter:

• WHO-Klassifikation der Tumoren des zentralen Nervensystems