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 (to 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%.

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 with respect to the gray matter Cystic component: hypointense Leptomeningeal involvement
T2	Solid component: iso- to hyperintense with respect 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).