Anaplastic Oligoastrocytoma (aMOA)

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Contents

Definition

Anaplastic Oligoastrocytoma is a mixed oligoastrocytoma with histological features of malignancy, such as increased cellularity, nuclear atypia, pleomorphism, and increased mitiotic activity. aMOA is a WHO Grade III glioma.

Epidemiology

No precise epidemiological data on aMOA are available.

Localization

Like oligodendrogliomas, aMOA are predominantly cerebral hemispheric tumors.

Clinical presentation

The typical time course of symptoms to presentation for patient with aMOA is relatively short, though some patients do present with an exacerbation of indolent symptoms, suggestive of a progressive tumor.

Imaging

aMOA appear as diffuse, irregular, contrast-enhancing lesions on MRI.

Macroscopy

MOA is macroscopically indistinguishable from an Anaplastic Astrocytoma (AA).

Histopathology

aMOA is histologically similar to an MOA, but with additional features of malignancy, such as increased cellularity, nuclear atypia, pleomorphism, and increased mitiotic activity. In addition, microvascular proliferation and necrosis may be present.

Molecular genetics

aMOAs have been found to share many alterations implicated in the progression of astrocytomas and oligodendrogliomas, including LOH on 9p and homozygous deletion of CDKN2A, as well as allelic loss on chromosomes 10 and 11p.

Prognosis

Median survival time following medical and surgical intervention is 2.8 years, with 5- and 10-year survival rates of 36% and 9%, respectively. Factors though to confer more favorable outcome include young age, chromosomes 1p and 19q deletion, and gross total surgical resection.

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