Pleomorphic xanthoastrocytoma

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Sujit Routray, M.D. [2]

Synonyms and keywords: Pleomorphic xanthoastrocytomas; PXA

Overview

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

Pathophysiology

Pathogenesis

• Pleomorphic xanthoastrocytoma is formed through the mitosis of the astrocytes.

Gross Pathology

• On gross pathology, polymorphic xanthoastrocytoma is characterized by a well circumscribed mass, often with cystic component and a superficially situated mural nodule, with involvement of the overlying leptomeninges.
• Polymorphic xanthoastrocytomas are almost invariably (98%) located supratentorially, typically located superficially (peripherally), involving the cortex and overlying leptomeninges. Approximately half are located in the temporal lobe.
• They are found commonly in the area of the temples, frontal lobe, or on top of the parietal lobe. In about 20% of cases, more than one lobe is involved.

Microscopic Pathology

• On microscopic histopathological analysis, polymorphic xanthoastrocytoma is characterized by:

• Ill-defined margins
• Spindle cells, polygonal cells, multi-nucleated cells, and lipid laden xanthomatous astrocytes
• Pleomorphic nuclei
• No endothelial proliferation or necrosis

Immunohistochemistry

• Polymorphic xanthoastrocytoma is demonstrated by positivity to tumor marker such as GFAP.

Differentiating Pleomorphic Xanthoastrocytoma from other Diseases

Pleomorphic xanthoastrocytoma must be differentiated from:

• Desmoplastic infantile ganglioglioma
• Neuroblastoma
• Extraventricular neurocytoma
• Dysembryoplastic neuroepithelial tumor (DNET)​
• Ganglioglioma
• Oligodendroglioma

Epidemiology and Demographics

Prevalence

• Pleomorphic xanthoastrocytoma constitutes approximately 1% of all primary brain tumors.

Age

• Pleomorphic xanthoastrocytoma is a rare disease that tends to affect the children and young adult population.
• The median age at diagnosis is 26 years.

Natural History, Complications and Prognosis

Natural History

• If left untreated, patients with pleomorphic xanthoastrocytoma may progress to develop seizures,

Complication

• Common complications of pleomorphic xanthoastrocytoma include:

• Local recurrence
• Malignant transformation (WHO grade III lesion or glioblastoma multiforme)

Prognosis

• Prognosis is generally good, and the 5-year survival rate of patients with pleomorphic xanthoastrocytoma is approximately 70-80%.

Symptoms

• Symptoms of pleomorphic xanthoastrocytoma include:

• Seizures with or without aura
• Headaches
• Amnesia
• Loss of consciousness
• Auditory sensations (sound or tune)
• Gustatory senasation (taste)
• Olfactory sensation (smell that is not truly present)
• Dysphoria or euphoria
• Motionless staring, automatic movements of the hands or mouth, inability to respond to others, unusual speech, or unusual behavior

CT

Head CT scan is helpful in the diagnosis of pleomorphic xanthoastrocytoma. On CT scan, pleomorphic xanthoastrocytoma is characterized by:

• Iso- or hypoattenuating mass
• Calcification
• Vivid enhancement on contrast administration

MRI

Brain MRI is helpful in the diagnosis of pleomorphic xanthoastrocytoma. On MRI, pleomorphic xanthoastrocytoma is characterized by:

MRI component	Findings
T1	Solid component: iso- to hypointense compared to the gray matter Cystic component: hypointense Leptomeningeal involvement
T2	Solid component: iso- to hyperintense compared to the gray matter Cystic component: hyperintense Mild surrounding vasogenic edema
T1 with contrast	Solid component: vivid enhancement

Digital subtraction angiography

• Digital subtraction angiography (DSA): Despite vivid enhancement, pleomorphic xanthoastrocytomas are usually avascular on angiography.

Positron Emission Tomography

• F-18 FDG PET images of pleomorphic xanthoastrocytoma demonstrates markedly decreased accumulation of [18F]-fluorodeoxyglucose (glucose hypometabolism).