Anaplastic Oligoastrocytoma (aMOA)
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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.
