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Pleomorphic xanthoastrocytoma

contributed by Dr Frank Gaillard on May 2, 2008

System: Central Nervous System

Pleomorphic xanthoastrocytoma (PXA) is type of rare low grade astrocytoma (WHO Grade II) found in young patients who typically present with temporal lobe epilepsy.

Demographics and clinical presentation

Typically these tumours are found in young patients (children or young adults), and as they have a predilection for the temporal lobe, they most frequently present with seizures ( 71 - 78% of cases ) 1,2.

They are rare tumours accounting for only approximately 1% of primary brain tumours 2,3.

Pathology

Macroscopically these tumours appear well circumscribed, often with cystic component and involvement of the overlying leptomeninges 1,3.

Microscopically the margins are not as well defined. Spindle cells, polygonal cells and multi-nucleated cells are identified. Even more pleomorphic is the appearance of the nuclei. 

These tumours are GFAP positive, although often only weakly 3.

Radiographic features

PXAs are almost invariably (98%) located supratentorially, typically located superficially (peripherally), involving the cortex and overlying leptomeninges. Approximately half are located in the temproal lobe 2. Often there is a cystic component ( 50 - 60% ) with an enhancing mural nodule. Additionally they are one of the tumours that may exhibit a dural tail, which is reactive rather than due to direct dural invasion, which is rare 2. 

CT

PXAs are typically hypo or isodense and may be well or poorly demarcated, usually with little surrounding oedema. Calcification is rare. Due to its superfical location it may cause scalloping of the overlying bone 2.

MRI
  • T1
    • iso to hypointense c.f. grey matter
    • solid component usually enhances vividly
    • leptomeningeal involvement seen in over 70% of cases 2
  • T2
DSA

Despite vivid enhancement, PXAs are usually avascular on angiography 2

Treatment and prognosis

Although prognosis is good following surgical excision, with a 5 year survival of 70 -80% 1,3, local recurrence and malignant transformation (to WHO grade III lesion or GBM) are not uncommon (up to 20% cases) 2

Neither radiotherapy nor chemotherapy have a significant effect on these tumours 2, although radiotherapy may have a role to play in patients with incomplete resection or those with recurrent disease 3. 

Differential diagnoses

See also